RIC Message Router – RMR

Please refer to the main RMR manual page for an overview of the library.

Installation Guide

The RMR shared-object library and supporting files including C-language header files for development are published as Debian (.deb) and Redhat Package Manager (.rpm) package files to PackageCloud . Follow the instructions there to download and install the required version. The commands to install a recent version on a Debian system such as Ubuntu appear next:

wget -nv --content-disposition https://packagecloud.io/o-ran-sc/release/packages/debian/stretch/rmr_4.0.5_amd64.deb/download.deb
sudo dpkg -i rmr_4.0.5_amd64.deb
wget -nv --content-disposition https://packagecloud.io/o-ran-sc/release/packages/debian/stretch/rmr-dev_4.0.5_amd64.deb/download.deb
sudo dpkg -i rmr-dev_4.0.5_amd64.deb

Configuration and Deployment

OVERVIEW

The RIC Message Router (RMR) is a library for peer-to-peer communication. Applications use the library to send and receive messages where the message routing and endpoint selection is based on the message type rather than DNS host name-IP port combinations.

This document contains information regarding the configuration of RMR when it is embedded by a user application . RMR itself is a library, not a deployable entity.

Configuration

Many aspects of RMR behavior are controlled via environment variables. These values are read when a user application invokes the RMR initialization function. This allows these variables to be set before the application is started as a function of the true environment, or set by the application as a means for the application to influence RMR’s behaviour. The following is a list of environment variables which RMR recognizes. Also see the main RMR manual page in the development package for more details.

RMR_ASYNC_CONN	Allows the async connection mode to be turned off (by setting the value to 0). When set to 1, or missing from the environment, RMR will invoke the connection interface in the transport mechanism using the non-blocking (async) mode. This will likely result in many “soft failures” (retry) until the connection is established, but allows the application to continue unimpeded should the connection be slow to set up.
RMR_BIND_IF	This provides the interface that RMR will bind listen ports to, allowing for a single interface to be used rather than listening across all interfaces. This should be the IP address assigned to the interface that RMR should listen on, and if not defined RMR will listen on all interfaces.
RMR_CTL_PORT	This variable defines the port that RMR should open for communications with Route Manager, and other RMR control applications. If not defined, the port 4561 is assumed. Previously, the RMR_RTG_SVC (route table generator service port) was used to define this port. However, a future version of Route Manager will require RMR to connect and request tables, thus that variable is now used to supply the Route Manager’s well-known address and port. To maintain backwards compatibility with the older Route Manager versions, the presence of this variable in the environment will shift RMR’s behaviour with respect to the default value used when RMR_RTG_SVC is not defined. When RMR_CTL_PORT is defined: RMR assumes that Route Manager requires RMR to connect and request table updates is made, and the default well-known address for Route manager is used (routemgr:4561). When RMR_CTL_PORT is undefined: RMR assumes that Route Manager will connect and push table updates, thus the default listen port (4561) is used. To avoid any possible misinterpretation and/or incorrect assumptions on the part of RMR, it is recommended that both the RMR_CTL_PORT and RMR_RTG_SVC be defined. In the case where both variables are defined, RMR will behave exactly as is communicated with the variable’s values.
RMR_RTREQ_FREQ	When RMR needs a new route table it will send a request once every n seconds. The default value for n is 5, but can be changed if this variable is set prior to invoking the process. Accepted values are between 1 and 300 inclusive.
RMR_RTG_SVC	The value of this variable depends on the Route Manager in use. When the Route Manager is expecting to connect to an xAPP and push route tables, this variable must indicate the port which RMR should use to listen for these connections. When the Route Manager is expecting RMR to connect and request a table update during initialisation, the variable should be the host of the Route Manager process. The RMR_CTL_PORT variable (added with the support of sending table update requests to Route manager), controls the behaviour if this variable is not set. See the description of that variable for details.
RMR_HR_LOG	By default RMR writes messages to standard error (incorrectly referred to as log messages) in human readable format. If this environment variable is set to 0, the format of standard error messages might be written in some format not easily read by humans. If missing, a value of 1 is assumed.
RMR_LOG_VLEVEL	This is a numeric value which corresponds to the verbosity level used to limit messages written to standard error. The lower the number the less chatty RMR functions are during execution. The following is the current relationship between the value set on this variable and the messages written: 0 Off; no messages of any sort are written. 1 Only critical messages are written (default if this variable does not exist) 2 Errors and all messages written with a lower value. 3 Warnings and all messages written with a lower value. 4 Informational and all messages written with a lower value. 5 Debugging mode – all messages written, however this requires RMR to have been compiled with debugging support enabled.
RMR_RTG_ISRAW	Deprecated. Should be set to 1 if the route table generator is sending “plain” messages (not using RMR to send messages), 0 if the RTG is using RMR to send. The default is 1 as we don’t expect the RTG to use RMR. This variable is only recognised when using the NNG transport library as it is not possible to support NNG “raw” communications with other transport libraries. It is also necessary to match the value of this variable with the capabilities of the Route Manager; at some point in the future RMR will assume that all Route Manager messages will arrive via an RMR connection and will ignore this variable.
RMR_SEED_RT	This is used to supply a static route table which can be used for debugging, testing, or if no route table generator process is being used to supply the route table. If not defined, no static table is used and RMR will not report ready until a table is received. The static route table may contain both the route table (between newrt start and end records), and the MEID map (between meid_map start and end records).
RMR_SRC_ID	This is either the name or IP address which is placed into outbound messages as the message source. This will used when an RMR based application uses the rmr_rts_msg() function to return a response to the sender. If not supplied RMR will use the hostname which in some container environments might not be routable. The value of this variable is also used for Route Manager messages which are sent via an RMR connection.
RMR_VCTL_FILE	This supplies the name of a verbosity control file. The core RMR functions do not produce messages unless there is a critical failure. However, the route table collection thread, not a part of the main message processing component, can write additional messages to standard error. If this variable is set, RMR will extract the verbosity level for these messages (0 is silent) from the first line of the file. Changes to the file are detected and thus the level can be changed dynamically, however RMR will only suss out this variable during initialisation, so it is impossible to enable verbosity after startup.
RMR_WARNINGS	If set to 1, RMR will write some warnings which are non-performance impacting. If the variable is not defined, or set to 0, RMR will not write these additional warnings.

User’s Guide

RIC Message Router – RMR

Overview

The RIC Message Router (RMR) is a library for peer-to-peer communication. Applications use the library to send and receive messages where the message routing and endpoint selection is based on the message type rather than DNS host name-IP port combinations. The library provides the following major features:

• Routing and endpoint selection is based on message type.

• Application is insulated from the underlying transport mechanism and/or protocols.

• Message distribution (round robin or fanout) is selectable by message type.

• Route management updates are received and processed asynchronously and without overt application involvement.

Purpose

RMR’s main purpose is to provide an application with the ability to send and receive messages to/from other peer applications with minimal effort on the application’s part. To achieve this, RMR manages all endpoint information, connections, and routing information necessary to establish and maintain communication. From the application’s point of view, all that is required to send a message is to allocate (via RMR) a message buffer, add the payload data, and set the message type. To receive a message, the application needs only to invoke the receive function; when a message arrives a message buffer will be returned as the function result.

Message Routing

Applications are required to place a message type into a message before sending, and may optionally add a subscription ID when appropriate. The combination of message type, and subscription ID are refered to as the message key, and is used to match an entry in a routing table which provides the possible endpoints expecting to receive messages with the matching key.

Round Robin Delivery

An endpoint from RMR’s perspective is an application to which RMR may establish a connection, and expect to send messages with one or more defined message keys. Each entry in the route table consists of one or more endpoint groups, called round robin groups. When a message matches a specific entry, the entry’s groups are used to select the destination of the message. A message is sent once to each group, with messages being balanced across the endpoints of a group via round robin selection. Care should be taken when defining multiple groups for a message type as there is extra overhead required and thus the overall message latency is somewhat increased.

Routing Table Updates

Route table information is made available to RMR a static file (loaded once), or by updates sent from a separate route manager application. If a static table is provided, it is loaded during RMR initialization and will remain in use until an external process connects and delivers a route table update (often referred to as a dynamic update). Dynamic updates are listened for in a separate process thread and applied automatically; the application does not need to allow for, or trigger, updates.

Latency And Throughput

While providing insulation from the underlying message transport mechanics, RMR must also do so in such a manner that message latency and throughput are not impacted. In general, the RMR induced overhead, incurred due to the process of selecting an endpoint for each message, is minimal and should not impact the overall latency or throughput of the application. This impact has been measured with test applications running on the same physical host and the average latency through RMR for a message was on the order of 0.02 milliseconds.

As an application’s throughput increases, it becomes easy for the application to overrun the underlying transport mechanism (e.g. NNG), consume all available TCP transmit buffers, or otherwise find itself in a situation where a send might not immediately complete. RMR offers different modes which allow the application to manage these states based on the overall needs of the application. These modes are discussed in the Configuration section of this document.

General Use

To use, the RMR based application simply needs to initialise the RMR environment, wait for RMR to have received a routing table (become ready), and then invoke either the send or receive functions. These steps, and some behind the scenes details, are described in the following paragraphs.

Initialisation

The RMR function rmr_init() is used to set up the RMR environment and must be called before messages can be sent or received. One of the few parameters that the application must communicate to RMR is the port number that will be used as the listen port for new connections. The port number is passed on the initialisation function call and a TCP listen socket will be opened with this port. If the port is already in use RMR will report a failure; the application will need to reinitialise with a different port number, abort, or take some other action appropriate for the application.

In addition to creating a TCP listen port, RMR will start a process thread which will be responsible for receiving dynamic updates to the route table. This thread also causes a TCP listen port to be opened as it is expected that the process which generates route table updates will connect and send new information when needed. The route table update port is not supplied by the application, but is supplied via an environment variable as this value is likely determined by the mechanism which is starting and configuring the application.

The RMR Context

On successful initialisation, a void pointer, often called a handle by some programming languages, is returned to the application. This is a reference to the RMR control information and must be passed as the first parameter on most RMR function calls. RMR refers to this as the context, or ctx.

Wait For Ready

An application which is only receiving messages does not need to wait for RMR to become ready after the call to the initialization function. However, before the application can successfully send a message, RMR must have loaded a route table, and the application must wait for RMR to report that it has done so. The RMR function rmr_ready() will return the value true (1) when a complete route table has been loaded and can be used to determine the endpoint for a send request.

Receiving Messages

The process of receiving is fairly straight forward. The application invokes the RMR rmr_rcv_msg() function which will block until a message is received. The function returns a pointer to a message block which provides all of the details about the message. Specifically, the application has access to the following information either directly or indirectly:

• The payload (actual data)

• The total payload length in bytes

• The number of bytes of the payload which contain valid data

• The message type and subscription ID values

• The hostname and IP address of the source of the message (the sender)

• The transaction ID

• Tracing data (if provided)

The Message Payload

The message payload contains the raw data that was sent by the peer application. The format will likely depend on the message type, and is expected to be known by the application. A direct pointer to the payload is available from the message buffer (see appendix B for specific message buffer details).

Two payload-related length values are also directly available: the total payload length, and the number of bytes actually filled with data. The used length is set by the caller, and may or not be an accurate value. The total payload length is determined when the buffer is created for sending, and is the maximum number of bytes that the application may modify should the buffer be used to return a response.

Message Type and Subscription ID

The message type and subscription ID are both directly available from the message buffer, and are the values which were used to by RMR in the sending application to select the endpoint. If the application resends the message, as opposed to returning the message buffer as a response, the message number and/or the subscription ID might need to be changed to avoid potential issues[1].

Sender Information

The source, or sender information, is indirectly available to the application via the rmr_get_src() and rmr_get_ip() functions. The former returns a string containing hostname:port, while the string ip:port is returned by the latter.

Transaction ID

The message buffer contains a fixed length set of bytes which applications can set to track related messages across the application concept of a transaction. RMR will use the transaction ID for matching a response message when the rmr_call() function is used to send a message.

Trace Information

RMR supports the addition of an optional trace information to any message. The presence and size is controlled by the application, and can vary from message to message if desired. The actual contents of the trace information is determined by the application; RMR provides only the means to set, extract, and obtain a direct reference to the trace bytes. The trace data field in a message buffer is discussed in greater detail in the Trace Data section.

Sending Messages

Sending requires only slightly more work on the part of the application than receiving a message. The application must allocate an RMR message buffer, populate the message payload with data, set the message type and length, and optionally set the subscription ID. Information such as the source IP address, hostname, and port are automatically added to the message buffer by RMR, so there is no need for the application to worry about these.

Message Buffer Allocation

The function rmr_msg_alloc() allocates a zero copy buffer and returns a pointer to the RMR rmr_mbuf_t structure. The message buffer provides direct access to the payload, length, message type and subscription ID fields. The buffer must be preallocated in order to allow the underlying transport mechanism to allocate the payload space from its internal memory pool; this eliminates multiple copies as the message is sent, and thus is more efficient.

If a message buffer has been received, and the application wishes to use the buffer to send a response, or to forward the buffer to another application, a new buffer does not need to be allocated. The application may set the necessary information (message type, etc.), and adjust the payload, as is necessary and then pass the message buffer to rmr_send_msg() or rmr_rts_msg() to be sent or returned to the sender.

Populating the Message Buffer

The application has direct access to several of the message buffer fields, and should set them appropriately.

len	This is the number of bytes that the application placed into the payload. Setting length to 0 is allowed, and length may be less than the allocated payload size.
mtype	The message type that RMR will use to determine the endpoint used as the target of the send.
sub_id	The subscription ID if the message is to be routed based on the combination of message type and subscription ID. If no subscription ID is valid for the message, the application should set the field with the RMR constant RMR_VOID_SUBID.
payload	The application should obtain the reference (pointer) to the payload from the message buffer and place any data into the payload. The application is responsible for ensuring that the maximum payload size is not exceeded. The application may obtain the maximum size via the rmr_payload_size() function.
trace data	Optionally, the application may add trace information to the message buffer.

Sending a Message Buffer

Once the application has populated the necessary bits of a message, it may be sent by passing the buffer to the rmr_send_msg() function. This function will select an endpoint to receive the message, based on message type and subscription ID, and will pass the message to the underlying transport mechanism for actual transmission on the connection. (Depending on the underlying transport mechanism, the actual connection to the endpoint may happen at the time of the first message sent to the endpoint, and thus the latency of the first send might be longer than expected.)

On success, the send function will return a reference to a message buffer; the status within that message buffer will indicate what the message buffer contains. When the status is RMR_OK the reference is to a new message buffer for the application to use for the next send; the payload size is the same as the payload size allocated for the message that was just sent. This is a convenience as it eliminates the need for the application to call the message allocation function at some point in the future, and assumes the application will send many messages which will require the same payload dimensions.

If the message contains any status other than RMR_OK, then the message could not be sent, and the reference is to the unsent message buffer. The value of the status will indicate whether the nature of the failure was transient ( RMR_ERR_RETRY) or not. Transient failures are likely to be successful if the application attempts to send the message at a later time. Unfortunately, it is impossible for RMR to know the exact transient failure (e.g. connection being established, or TCP buffer shortage), and thus it is not possible to communicate how long the application should wait before attempting to resend, if the application wishes to resend the message. (More discussion with respect to message retries can be found in the Handling Failures section.)

Advanced Usage

Several forms of usage fall into a more advanced category and are described in the following sections. These include blocking call, return to sender and wormhole functions.

The Call Function

The RMR function rmr_call() sends a message in the exact same manner as the rmr_send_msg()() function, with the endpoint selection based on the message key. But unlike the send function, rmr_call() will block and wait for a response from the application that is selected to receive the message. The matching message is determined by the transaction ID which the application must place into the message buffer prior to invoking rmr_call(). Similarly, the responding application must ensure that the same transaction ID is placed into the message buffer before returning its response.

The return from the call is a message buffer with the response message; there is no difference between a message buffer returned by the receive function and one returned by the rmr_call() function. If a response is not received in a reasonable amount of time, a nil message buffer is returned to the calling application.

Returning a Response

Because of the nature of RMR’s routing policies, it is generally not possible for an application to control exactly which endpoint is sent a message. There are cases, such as responding to a message delivered via rmr_call() that the application must send a message and guarantee that RMR routes it to an exact destination. To enable this, RMR provides the rmr_rts_msg(), return to sender, function. Upon receipt of any message, an application may alter the payload, and if necessary the message type and subscription ID, and pass the altered message buffer to the rmr_rts_msg() function to return the altered message to the application which sent it. When this function is used, RMR will examine the message buffer for the source information and use that to select the connection on which to write the response.

Multi-threaded Calls

The basic call mechanism described above is not thread safe, as it is not possible to guarantee that a response message is delivered to the correct thread. The RMR function rmr_mt_call() accepts an additional parameter which identifies the calling thread in order to ensure that the response is delivered properly. In addition, the application must specifically initialise the multi-threaded call environment by passing the RMRFL_MTCALL flag as an option to the rmr_init() function.

One advantage of the multi-threaded call capability in RMR is the fact that only the calling thread is blocked. Messages received which are not responses to the call are continued to be delivered via normal rmr_rcv_msg() calls.

While the process is blocked waiting for the response, it is entirely possible that asynchronous, non-matching, messages will arrive. When this happens, RMR will queues the messages and return them to the application over the next calls to rmr_rcv_msg().

Wormholes

As was mentioned earlier, the design of RMR is to eliminate the need for an application to know a specific endpoint, even when a response message is being sent. In some rare cases it may be necessary for an application to establish a direct connection to an RMR-based application rather than relying on message type and subscription ID based routing. The wormhole functions provide an application with the ability to create a direct connection and then to send and receive messages across the connection. The following are the RMR functions which provide wormhole communications:

rmr_wh_open	Open a connection to an endpoint. Name or IP address and port of the endpoint is supplied. Returns a wormhole ID that the application must use when sending a direct message.
rmr_wh_send_msg	Sends an RMR message buffer to the connected application. The message type and subscription ID may be set in the message, but RMR will ignore both.
rmr_wh_close	Closes the direct connection.

Handling Failures

The vast majority of states reported by RMR are fatal; if encountered during setup or initialization, then it is unlikely that any message oriented processing should continue, and when encountered on a message operation continued operation on that message should be abandoned. Specifically with regard to message sending, it is very likely that the underlying transport mechanism will report a soft, or transient, failure which might be successful if the operation is retried at a later point in time. The paragraphs below discuss the methods that an application might deal with these soft failures.

Failure Notification

When a soft failure is reported, the returned message buffer returned by the RMR function will be RMR_ERR_RETRY. These types of failures can occur for various reasons; one of two reasons is typically the underlying cause:

• The session to the targeted recipient (endpoint) is not connected.

• The transport mechanism buffer pool is full and cannot accept another buffer.

Unfortunately, it is not possible for RMR to determine which of these two cases is occurring, and equally as unfortunate the time to resolve each is different. The first, no connection, may require up to a second before a message can be accepted, while a rejection because of buffer shortage is likely to resolve in less than a millisecond.

Application Response

The action which an application takes when a soft failure is reported ultimately depends on the nature of the application with respect to factors such as tolerance to extended message latency, dropped messages, and over all message rate.

RMR Retry Modes

In an effort to reduce the workload of an application developer, RMR has a default retry policy such that RMR will attempt to retransmit a message up to 1000 times when a soft failure is reported. These retries generally take less than 1 millisecond (if all 1000 are attempted) and in most cases eliminates nearly all reported soft failures to the application. When using this mode, it might allow the application to simply treat all bad return values from a send attempt as permanent failures.

If an application is so sensitive to any delay in RMR, or the underlying transport mechanism, it is possible to set RMR to return a failure immediately on any kind of error (permanent failures are always reported without retry). In this mode, RMR will still set the state in the message buffer to RMR_ERR_RETRY, but will not make any attempts to resend the message. This zero-retry policy is enabled by invoking the rmr_set_stimeout() with a value of 0; this can be done once immediately after rmr_init() is invoked.

Regardless of the retry mode which the application sets, it will ultimately be up to the application to handle failures by queuing the message internally for resend, retrying immediately, or dropping the send attempt all together. As stated before, only the application can determine how to best handle send failures.

Other Failures

RMR will return the state of processing for message based operations (send/receive) as the status in the message buffer. For non-message operations, state is returned to the caller as the integer return value for all functions which are not expected to return a pointer (e.g. rmr_init().) The following are the RMR state constants and a brief description of their meaning.

RMR_OK	state is good; operation finished successfully
RMR_ERR_BADARG	argument passed to function was unusable
RMR_ERR_NOENDPT	send/call could not find an endpoint based on msg type
RMR_ERR_EMPTY	msg received had no payload; attempt to send an empty message
RMR_ERR_NOHDR	message didn’t contain a valid header
RMR_ERR_SENDFAILED	send failed; errno may contain the transport provider reason
RMR_ERR_CALLFAILED	unable to send the message for a call function; errno may contain the transport provider reason
RMR_ERR_NOWHOPEN	no wormholes are open
RMR_ERR_WHID	the wormhole id provided was invalid
RMR_ERR_OVERFLOW	operation would have busted through a buffer/field size
RMR_ERR_RETRY	request (send/call/rts) failed, but caller should retry (EAGAIN for wrappers)
RMR_ERR_RCVFAILED	receive failed (hard error)
RMR_ERR_TIMEOUT	response message not received in a reasonable amount of time
RMR_ERR_UNSET	the message hasn’t been populated with a transport buffer
RMR_ERR_TRUNC	length in the received buffer is longer than the size of the allocated payload, received message likely truncated (length set by sender could be wrong, but we can’t know that)
RMR_ERR_INITFAILED	initialisation of something (probably message) failed
RMR_ERR_NOTSUPP	the request is not supported, or RMR was not initialised for the request

Depending on the underlying transport mechanism, and the nature of the call that RMR attempted, the system errno value might reflect additional detail about the failure. Applications should not rely on errno as some transport mechanisms do not set it with any consistency.

Configuration and Control

With the assumption that most RMR based applications will be executed in a containerised environment, there are some underlying mechanics which the developer may need to know in order to properly provide a configuration specification to the container management system. The following paragraphs briefly discuss these.

TCP Ports

RMR requires two (2) TCP listen ports: one for general application-to-application communications and one for route-table updates. The general communication port is specified by the application at the time RMR is initialised. The port used to listen for route table updates is likely to be a constant port shared by all applications provided they are running in separate containers. To that end, the port number defaults to 4561, but can be configured with an environment variable (see later paragraph in this section).

Host Names

RMR is typically host name agnostic. Route table entries may contain endpoints defined either by host name or IP address. In the container world the concept of a service name might exist, and likely is different than a host name. RMR’s only requirement with respect to host names is that a name used on a route table entry must be resolvable via the gethostbyname system call.

Environment Variables

Several environment variables are recognised by RMR which, in general, are used to define interfaces and listen ports (e.g. the route table update listen port), or debugging information. Generally this information is system controlled and thus RMR expects this information to be defined in the environment rather than provided by the application. The following is a list of the environment variables which RMR recognises:

RMR_BIND_IF	The interface to bind to listen ports to. If not defined 0.0.0.0 (all interfaces) is assumed.
RMR_RTG_SVC	This variabe supplies the host:port (or address:port) of the Route Manager (route table generator) process. RMR will attempt to connect to this address port combination and request a route table. If it is desired to prevent RMR from attempting to request a dynamic route table, the value of this variable should be set to “-1.” If not set routemgr is assumed.
RMR_CTL_PORT	This is the port which RMR’s route table collector thread will use to listen for RMR messages from the route manager (route table generator). By default this is 4561, and must be unique for each RMR process running on the host/container.
RMR_RTREQ_FREQ	When a new route table is needed, the frequency that RMR sends a route table request to the Route Manager defaults to 5 seconds. This variable can be used to set the frequency to a value between 1 and 300 seconds inclusive.
RMR_SEED_RT	Where RMR expects to find the name of the seed (static) route table. If not defined no static table is read.
RMR_RTG_ISRAW	If the value set to 0, RMR expects the route table manager messages to be messages with and RMR header. If this is not defined messages are assumed to be “raw” (without an RMR header.
RMR_VCTL_FILE	Provides a file which is used to set the verbose level of the route table collection thread. The first line of the file is read and expected to contain an integer value to set the verbose level. The value may be changed at any time and the route table thread will adjust accordingly.
RMR_SRC_NAMEONLY	If the value of this variable is greater than 0, RMR will not permit the IP address to be sent as the message source. Only the host name will be sent as the source in the message header.

Logging

RMR does not use any logging libraries; any error or warning messages are written to standard error. RMR messages are written with one of three prefix strings:

[CRI]	The event is of a critical nature and it is unlikely that RMR will continue to operate correctly if at all. It is almost certain that immediate action will be needed to resolve the issue.
[ERR]	The event is not expected and RMR is not able to handle it. There is a small chance that continued operation will be negatively impacted. Eventual action to diagnose and correct the issue will be necessary.
[WRN]	The event was not expected by RMR, but can be worked round. Normal operation will continue, but it is recommended that the cause of the problem be investigated.

Notes

[1] It is entirely possible to design a routing table, and application group, such that the same message type is is left unchanged and the message is forwarded by an application after updating the payload. This type of behaviour is often referred to as service chaining, and can be done without any “knowledge” by an application with respect to where the message goes next. Service chaining is supported by RMR in as much as it allows the message to be resent, but the actual complexities of designing and implementing service chaining lie with the route table generator process.

Appendix A – Quick Reference

Please refer to the RMR manual pages on the Read the Docs site

https://docs.o-ran-sc.org/projects/o-ran-sc-ric-plt-lib-rmr/en/latest/index.html

Appendix B – Message Buffer Details

The RMR message buffer is a C structure which is exposed in the rmr.h header file. It is used to manage a message received from a peer endpoint, or a message that is being sent to a peer. Fields include payload length, amount of payload actually used, status, and a reference to the payload. There are also fields which the application should ignore, and could be hidden in the header file, but we chose not to. These fields include a reference to the RMR header information, and to the underlying transport mechanism message struct which may or may not be the same as the RMR header reference.

The Structure

The following is the C structure. Readers are cautioned to examine the rmr.h header file directly; the information here may be out of date (old document in some cache), and thus it may be incorrect.

typedef struct {
    int    state;            // state of processing
    int    mtype;            // message type
    int    len;              // length of data in the payload (send or received)
    unsigned char* payload;  // transported data
    unsigned char* xaction;  // pointer to fixed length transaction id bytes
    int    sub_id;           // subscription id
    int    tp_state;         // transport state (errno)

                             // these things are off limits to the user application
    void*    tp_buf;         // underlying transport allocated pointer (e.g. nng message)
    void*    header;         // internal message header (whole buffer: header+payload)
    unsigned char* id;       // if we need an ID in the message separate from the xaction id
    int      flags;          // various MFL_ (private) flags as needed
    int      alloc_len;      // the length of the allocated space (hdr+payload)
    void*    ring;           // ring this buffer should be queued back to
    int      rts_fd;         // SI fd for return to sender
    int      cookie;         // cookie to detect user misuse of free'd msg
} rmr_mbuf_t;

State vs Transport State

The state field reflects the state at the time the message buffer is returned to the calling application. For a send operation, if the state is not RMR_OK then the message buffer references the payload that could not be sent, and when the state is RMR_OK the buffer references a fresh payload that the application may fill in.

When the state is not RMR_OK, C programmes may examine the global errno value which RMR will have left set, if it was set, by the underlying transport mechanism. In some cases, wrapper modules are not able to directly access the C-library errno value, and to assist with possible transport error details, the send and receive operations populate tp_state with the value of errno.

Regardless of whether the application makes use of the tp_state, or the errno value, it should be noted that the underlying transport mechanism may not actually update the errno value; in other words: it might not be accurate. In addition, RMR populates the tp_state value in the message buffer only when the state is not RMR_OK.

Field References

The transaction field was exposed in the first version of RMR, and in hindsight this shouldn’t have been done. Rather than break any existing code the reference was left, but additional fields such as trace data, were not directly exposed to the application. The application developer is strongly encouraged to use the functions which get and set the transaction ID rather than using the pointer directly; any data overruns will not be detected if the reference is used directly.

In contrast, the payload reference should be used directly by the application in the interest of speed and ease of programming. The same care to prevent writing more bytes to the payload buffer than it can hold must be taken by the application. By the nature of the allocation of the payload in transport space, RMR is unable to add guard bytes and/or test for data overrun.

Actual Transmission

When RMR sends the application’s message, the message buffer is not transmitted. The transport buffer (tp_buf) which contains the RMR header and application payload is the only set of bytes which are transmitted. While it may seem to the caller like the function rmr_send_msg() is returning a new message buffer, the same struct is reused and only a new transport buffer is allocated. The intent is to keep the alloc/free cycles to a minimum.

Appendix C – Glossary

Many terms in networking can be interpreted with multiple meanings, and several terms used in various RMR documentation are RMR specific. The following definitions are the meanings of terms used within RMR documentation and should help the reader to understand the intent of meaning.

application	A programme which uses RMR to send and/or receive messages to/from another RMR based application.
Critical error	An error that RMR has encountered which will prevent further successful processing by RMR. Critical errors usually indicate that the application should abort.
Endpoint	An RMR based application that is defined as being capable of receiving one or more types of messages (as defined by a routing key.)
Environment variable	A key/value pair which is set externally to the application, but which is available to the application (and referenced libraries) through the getenv system call. Environment variables are the main method of communicating information such as port numbers to RMR.
Error	An abnormal condition that RMR has encountered, but will not affect the overall processing by RMR, but may impact certain aspects such as the ability to communicate with a specific endpoint. Errors generally indicate that something, usually external to RMR, must be addressed.
Host name	The name of the host as returned by the gethostbyname system call. In a containerised environment this might be the container or service name depending on how the container is started. From RMR’s point of view, a host name can be used to resolve an endpoint definition in a route table.)
IP	Internet protocol. A low level transmission protocol which governs the transmission of datagrams across network boundaries.
Listen socket	A TCP socket used to await incoming connection requests. Listen sockets are defined by an interface and port number combination where the port number is unique for the interface.
Message	A series of bytes transmitted from the application to another RMR based application. A message is comprised of RMR specific data (a header), and application data (a payload).
Message buffer	A data structure used to describe a message which is to be sent or has been received. The message buffer includes the payload length, message type, message source, and other information.
Message type	A signed integer (0-32000) which identifies the type of message being transmitted, and is one of the two components of a routing key. See Subscription ID.
Payload	The portion of a message which holds the user data to be transmitted to the remote endpoint. The payload contents are completely application defined.
RMR context	A set of information which defines the current state of the underlying transport connections that RMR is managing. The application will be give a context reference (pointer) that is supplied to most RMR functions as the first parameter.
Round robin	The method of selecting an endpoint from a list such that all endpoints are selected before starting at the head of the list.
Route table	A series of “rules” which define the possible endpoints for each routing key.
Route table manager	An application responsible for building a route table and then distributing it to all applicable RMR based applications.
Routing	The process of selecting an endpoint which will be the recipient of a message.
Routing key	A combination of message type and subscription ID which RMR uses to select the destination endpoint when sending a message.
Source	The sender of a message.
Subscription ID	A signed integer value (0-32000) which identifies the subscription characteristic of a message. It is used in conjunction with the message type to determine the routing key.
Target	The endpoint selected to receive a message.
TCP	Transmission Control Protocol. A connection based internet protocol which provides for lossless packet transportation, usually over IP.
Thread	Also called a process thread, or pthread. This is a lightweight process which executes in concurrently with the application and shares the same address space. RMR uses threads to manage asynchronous functions such as route table updates.
Trace information	An optional portion of the message buffer that the application may populate with data that allows for tracing the progress of the transaction or application activity across components. RMR makes no use of this data.
Transaction ID	A fixed number of bytes in the message buffer) which the application may populate with information related to the transaction. RMR makes use of the transaction ID for matching response messages with the &c function is used to send a message.
Transient failure	An error state that is believed to be short lived and that the operation, if retried by the application, might be successful. C programmers will recognise this as EAGAIN.
Warning	A warning occurs when RMR has encountered something that it believes isn’t correct, but has a defined work round.
Wormhole	A direct connection managed by RMR between the user application and a remote, RMR based, application.

Appendix D – Code Examples

The following snippet of code illustrate some of the basic operation of the RMR library. Please refer to the examples and test directories in the RMR repository for complete RMR based programmes.

Sender Sample

The following code segment shows how a message buffer can be allocated, populated, and sent. The snippet also illustrates how the result from the rmr_send_msg() function is used to send the next message. It does not illustrate error and/or retry handling.

#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <time.h>

#include <rmr/rmr.h>

int main( int argc, char** argv ) {
    void* mrc;                            // msg router context
    struct epoll_event events[1];        // list of events to give to epoll
    struct epoll_event epe;                // event definition for event to listen to
    int     ep_fd = -1;                    // epoll's file des (given to epoll_wait)
    int rcv_fd;                            // file des for epoll checks
    int nready;                            // number of events ready for receive
    rmr_mbuf_t*        sbuf;                // send buffer
    rmr_mbuf_t*        rbuf;                // received buffer
    int    count = 0;
    int    rcvd_count = 0;
    char*    listen_port = "43086";
    int        delay = 1000000;            // mu-sec delay between messages
    int        mtype = 0;
    int        stats_freq = 100;

    if( argc > 1 ) {                    // simplistic arg picking
        listen_port = argv[1];
    }
    if( argc > 2 ) {
        delay = atoi( argv[2] );
    }
    if( argc > 3 ) {
        mtype = atoi( argv[3] );
    }

    fprintf( stderr, "<DEMO> listen port: %s; mtype: %d; delay: %d\\n",
        listen_port, mtype, delay );

    if( (mrc = rmr_init( listen_port, 1400, RMRFL_NONE )) == NULL ) {
        fprintf( stderr, "<DEMO> unable to initialise RMR\\n" );
        exit( 1 );
    }

    rcv_fd = rmr_get_rcvfd( mrc );  // set up epoll things, start by getting the FD from RMR
    if( rcv_fd < 0 ) {
        fprintf( stderr, "<DEMO> unable to set up polling fd\\n" );
        exit( 1 );
    }
    if( (ep_fd = epoll_create1( 0 )) < 0 ) {
        fprintf( stderr, "[FAIL] unable to create epoll fd: %d\\n", errno );
        exit( 1 );
    }
    epe.events = EPOLLIN;
    epe.data.fd = rcv_fd;

    if( epoll_ctl( ep_fd, EPOLL_CTL_ADD, rcv_fd, &epe ) != 0 )  {
        fprintf( stderr, "[FAIL] epoll_ctl status not 0 : %s\\n", strerror( errno ) );
        exit( 1 );
    }

    sbuf = rmr_alloc_msg( mrc, 256 );    // alloc 1st send buf; subsequent bufs alloc on send
    rbuf = NULL;                        // don't need to alloc receive buffer

    while( ! rmr_ready( mrc ) ) {        // must have route table
        sleep( 1 );                        // wait til we get one
    }
    fprintf( stderr, "<DEMO> rmr is ready\\n" );


    while( 1 ) {            // send messages until the cows come home
        snprintf( sbuf->payload, 200,
            "count=%d received= %d ts=%lld %d stand up and cheer!",    // create the payload
            count, rcvd_count, (long long) time( NULL ), rand() );

        sbuf->mtype = mtype;                            // fill in the message bits
        sbuf->len =  strlen( sbuf->payload ) + 1;        // send full ascii-z string
        sbuf->state = 0;
        sbuf = rmr_send_msg( mrc, sbuf );                // send & get next buf to fill in
        while( sbuf->state == RMR_ERR_RETRY ) {            // soft failure (device busy?) retry
            sbuf = rmr_send_msg( mrc, sbuf );            // w/ simple spin that doesn't give up
        }
        count++;

        // check to see if anything was received and pull all messages in
        while( (nready = epoll_wait( ep_fd, events, 1, 0 )) > 0 ) { // 0 is non-blocking
            if( events[0].data.fd == rcv_fd ) {     // waiting on 1 thing, so [0] is ok
                errno = 0;
                rbuf = rmr_rcv_msg( mrc, rbuf );    // receive and ignore; just count
                if( rbuf ) {
                    rcvd_count++;
                }
            }
        }

        if( (count % stats_freq) == 0 ) {            // occasional stats out to tty
            fprintf( stderr, "<DEMO> sent %d   received %d\\n", count, rcvd_count );
        }

        usleep( delay );
    }
}

Receiver Sample

The receiver code is even simpler than the sender code as it does not need to wait for a route table to arrive (only senders need to do that), nor does it need to allocate an initial buffer. The example assumes that the sender is transmitting a zero terminated string as the payload.

#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#include <rmr/rmr.h>


int main( int argc, char** argv ) {
    void* mrc;                     // msg router context
    long long total = 0;
    rmr_mbuf_t* msg = NULL;        // message received
    int stat_freq = 10;            // write stats after reciving this many messages
    int i;
    char*    listen_port = "4560"; // default to what has become the standard RMR port
    long long count = 0;
    long long bad = 0;
    long long empty = 0;

    if( argc > 1 ) {
        listen_port = argv[1];
    }
    if( argc > 2 ) {
        stat_freq = atoi( argv[2] );
    }
    fprintf( stderr, "<DEMO> listening on port: %s\\n", listen_port );
    fprintf( stderr, "<DEMO> stats will be reported every %d messages\\n", stat_freq );

    mrc = rmr_init( listen_port, RMR_MAX_RCV_BYTES, RMRFL_NONE );
    if( mrc == NULL ) {
        fprintf( stderr, "<DEMO> ABORT:  unable to initialise RMr\\n" );
        exit( 1 );
    }

    while( ! rmr_ready( mrc ) ) {    // wait for RMR to get a route table
        fprintf( stderr, "<DEMO> waiting for ready\\n" );
        sleep( 3 );
    }
    fprintf( stderr, "<DEMO> rmr now shows ready\\n" );

    while( 1 ) {                              // receive until killed
        msg = rmr_rcv_msg( mrc, msg );        // block until one arrives

        if( msg ) {
            if( msg->state == RMR_OK ) {
                count++;                      // nothing fancy, just count
            } else {
                bad++;
            }
        } else {
            empty++;
        }

        if( (count % stat_freq) == 0  ) {
            fprintf( stderr, "<DEMO> total received: %lld; errors: %lld; empty: %lld\\n",
                count, bad, empty );
        }
    }
}

Receive and Send Sample

The following code snippet receives messages and responds to the sender if the message type is odd. The code illustrates how the received message may be used to return a message to the source. Variable type definitions are omitted for clarity and should be obvious.

It should also be noted that things like the message type which id returned to the sender (99) is a random value that these applications would have agreed on in advance and is not an RMR definition.

mrc = rmr_init( listen_port, MAX_BUF_SZ, RMRFL_NOFLAGS );
rmr_set_stimeout( mrc, 1 );        // allow RMR to retry failed sends for ~1ms

while( ! rmr_ready( mrc ) ) {        // we send, therefore we need a route table
    sleep( 1 );
}

mbuf = NULL;                        // ensure our buffer pointer is nil for 1st call

while( TRUE ) {
    mbuf = rmr_rcv_msg( mrc, mbuf );        // wait for message

    if( mbuf == NULL || mbuf->state != RMR_OK ) {
        break;
    }

    if( mbuf->mtype % 2 ) {                // respond to odd message types
        plen = rmr_payload_size( mbuf );        // max size

                                                // reset necessary fields in msg
        mbuf->mtype = 99;                       // response type
        mbuf->sub_id = RMR_VOID_SUBID;          // we turn subid off
        mbuf->len = snprintf( mbuf->payload, plen, "pong: %s", get_info() );

        mbuf = rmr_rts_msg( mrc, mbuf );        // return to sender
        if( mbuf == NULL || mbuf->state != RMR_OK ) {
            fprintf( stderr, "return to sender failed\\n" );
        }
    }
}

fprintf( stderr, "abort: receive failure\\n" );
rmr_close( mrc );

Developer’s Guide

OVERVIEW

The RIC Message Router (RMR) is a library for peer-to-peer communication. Applications use the library to send and receive messages where the message routing and endpoint selection is based on the message type rather than DNS host name-IP port combinations.

This document contains information that developers need to know to contribute to the RMR project.

Language

RMR is written in C, and thus a contributing developer to the core library should have an excellent working knowledge of C. There currently is one set of cross-languages bindings supporting Python, and a developer wishing to contribute to the bindings source should be familiar with Python (version 3.7+) and with the Python ctypes library.

Code Structure

RMR is designed to provide an insulation layer between user applications and the actual transport mechanism. Initially RMR was built on top of the third-party library Nanosmg, shortly after was ported to the third-party library NNG (Nanomsg Next Generation), and then was ported to an internally developed socket library called SI95. RMR presents the same API to the user application regardless of the underlying transport library, but the resulting output when compiling RMR is always a transport-specific library. As an example, librmr_nng.a is the library generated for use with the NNG transport.

As such the library source is organised into multiple components:

common	Source in the common directory is agnostic to the underlying transport mechanism (Nanomsg, NNG, SI95, ..), and thus can be used when generating either library.
nano	Source which is tightly coupled with the underlying Nanomsg library. (Nanomsg has been deprecated, but the RMR source remains as an example.)
nng	Source which is tightly coupled with the underlying NNG library. (NNG has been deprecated, but the RMR source remains as an example.)
si	Source which is tightly coupled with the underlying SI95 library.

Internal Function Exposure

The decision to limit as much as practical the exposure of truly internal RMR functions was made, and as a result most of the RMR functions carry a static label. In order to modularise the code as much as possible, this means that the primary module (e.g. rmr_nng.c) directly includes other RMR modules, rather than depending on referencing the internal functions during linking. While this is an infrequently used approach, it does mean that there are very few functions visible for the user application to reference, all of them having the prefix rmr\$1_. This allows internal functions to have shorter names while still being meaningful.

Coding Style

There is a list of coding style guidelines in the top level directory, and as such they are not expanded upon here. The general practice is to follow the style when editing an existing module, respect the author’s choice where style alternatives are not frowned upon. When creating new modules, select a style that fits the guidelines and is easy for you to work with. There are a few things that the RMR maintainers insist on, but for the most part style is up to the creator of a module.

Building

RMR is constructed using CMake. While CMake’s project description can be more cumbersome than most typical Makefiles, the tool provides convenience especially when it comes to creating DEB/RPM packages.

Route Table Guide

RIC Message Router – RMR

Overview

Messages sent via the RIC Message Router (RMR) are routed to an endpoint (another application) based on a combination of the message type (MT) and subscription ID (SID) supplied in the message. RMR determines the endpoint by matching the MT and SID combination to an entry in a route table which has been supplied dynamically by a Route Manager service, or as a static table loaded during RMR initialisation. It is also possible to route messages directly to an endpoint which is the managed entity “owner,” using the managed entity ID (MEID).

For most xAPP developers the format of the RMR route table is not important beyond understanding how to create a static table for local testing. For developers of a Route Manager service, the need is certainly a requirement. This document describes the overall syntax of a route table and the interface between the Route Manager service and RMR.

Contents of a Route Table

The table consists of a start record, one or more entry records, and an end record. Each entry record defines one message type, with an optional sender application, and the endpoint(s) which accept the indicated message type. All table records contain fields separated with vertical bars (|), and allow for trailing comments with the standard shell comment symbol (hash, #) provided that the start of the comment is separated from the last token on the record by one or more spaces. Leading and trailing white space in each field is ignored. Figure 1 illustrates a very basic route table with two message types, 1000 and 2000, and two subscription IDs for message type 1000.

newrt | start | rt-0928
rte   | 2000  | logger:30311
mse   | 1000  | 10 | forwarder:43086
mse   | 1000  | 21 | app0:43086,app1:43086
newrt | end   | 3

Figure 1: A basic route table.

Entry record syntax

Two types of table entries are supported for compatibility with the original RMR implementation, but only the mse entry type is needed and that should be the entry used when creating new tables. The following shows the syntax for both entry types:

rte | <msg-type>[,<sender-endpoint>] | <endpoint-group>[;<endpoint-group>;...]
mse | <msg-type>[,<sender-endpoint>] | <sub-id> | <endpoint-group>[;<endpoint-group>;...]

Where:

mse, rte	is the table entry type
<msg-type>	is the integer message type
<sender-endpoint>	is the endpoint description of the message sender; only that sender will read the entry from the table, so a single table may be used for all senders when a common message type is delivered to varying endpoints based on senders. If the sender endpoint is omitted from the entry, then the entry will be used by all applications.
<sub-id>	is the subscription id (integer) for subscription-based messages, or -1 if the message type is not subscription-based. An mse entry with a sub-id of -1 is the same as an rte entry with the same message type.
<endpoint-group>	is one or more, comma separated, endpoint descriptions.

When an application sends a message with the indicated type, the message will be sent to one endpoint in the group in a round-robin ordering. If multiple endpoint groups are given, then the message is sent to a member selected from each group; 3 groups, then three messages will be sent. The first group is required.

Line separation

Table entries must end with a record termination sequence which may be one of the following three sequences:

• a single newline (\n)

• a DOS style CRLF pair (\r\n)

• a single carriage return (\r)

Care must be taken when manually editing a static table; some editors do not add a final record termination sequence to the last line of a file. RMR expects the final record to have a termination sequence to ensure that the record was not truncated (especially important when receiving dynamic tables).

Table framing

The route table parser within RMR assumes that route table entries are sent via RMR messages as a stream. To ensure synchronisation and prevent malformed tables because of broken sessions or lost packets, each table must begin and end with an newrt record. Each newrt record has one of two possible syntax layouts as described below.

newrt | begin [| table-id-string]
newrt | end  [| record-count]

Figure 2: Illustration of the newrt records in the table.

The table-id-string is an optional string which is used by RMR when sending an acknowledgement back to the Route Manager service (see the Route Manager Interface section for more details). If a record-count is given as the final field on the end record, RMR will verify that the number of mse and rte entries in the table matches the count; if there is a mismatch in values the table is not used.

Comments, spaces, and blank lines

Comments may be placed to the right of any table entry line using the standard shell comment symbol (#). The start of a comment must be separated from any previous record content by at least one space or tab. Complete lines are treated as comments when the first non-whitespace character of a line is a comment symbol. Blank lines are also ignored.

Fields on table records are separated using the vertical bar (|) character. Any white space (tabs or spaces) which appear immediately before or after a separator are ignored.

Endpoint Description

The endpoint description is either the hostname or IP address followed by a port number; the two are separated by a single colon. The illustration below assumes that host names (e.g. forwarder and app1) are defined; they also make the tables easier to read. The port number given is the port number that the user application provides to RMR when the RMR initialisation function is invoked (and thus is the port that RMR is listening on).

Table Mechanics

Creating a table from the two entry types is fairly simple, however there are some subtleties which should be pointed out to avoid unexpected behaviour. For this discussion the following complete table will be used.

newrt | start | rt-0928 rte | 2000 | logger:30311 mse | 1000 | 10 | forwarder:43086 mse | 1000,forwarder:43086 | 10 | app2:43086 mse | 1000 | -1 | app0:43086,app1:43086; logger:20311 newrt | end | 4

(1) (2) (3) (4) (5) (6)

Figure 3: A complete RMR routing table (line numbers to the right for reference).

Table Entry Ordering

Whether a table is read from a file on disk, or is received from a Route Manager service, RMR parses the records to build an internal route table keeping only the relevant information. Entries are read in the order they appear (from the file or in messages received), and RMR will use only one entry for each MT/SID pair.

For most tables, the ordering of entries is not important, but when there are entries which duplicate the MT/SID pair ordering becomes significant. RMR will use the last valid entry for a MT/SID pair that it encounters. An entry is considered valid if there is no sender identified with the message type (line 3), and when the sender (host and port) match the the applications’ location and the port provided to RMR for listening.

Using the table in figure 3 as an example, there are two entries which match the MT/SID pair of 1000/10. When this table is parsed on any host, RMR will recognise and add the first entry (line 3) to the internal representation; this entry is valid for all applications. The second 1000/10 entry (line 4) is valid when the table is parsed on the forwarder host, and only by the application which is listening on port 43086. For this application the entry will override the more generic entry for the MT/SID combination.

As a rule, the ordering of entries for a given MT/SID pair should be from most generic to most specific.

Route Manager Communications

During initialisation RMR will use the value of the RMR_RTG_SVC environment variable to connect to the Route Manager service in order to request a route table. The connection between RMR and the Route Manager is also an RMR session and thus RMR messages will be used to exchange requests and responses.

Table Request

During initialisation, RMR establishes a wormhole connection to the Route Manager and sends a message type of 21 to request a new table. RMR will continue to send table requests until a table is received and accepted; in other words it is fine for the Route Manager to ignore the requests if it is not ready to respond.

Sending Tables To RMR

Table entry data is expected to arrive via RMR message with a message type of 20. The message may contain one or more entries provided that the entries are newline separated. Current versions of RMR support very large messages, however to ensure compatibility with an xAPP built using an older version of RMR (pre 3.8), messages should be limited to 4 KiB.

Table Acceptance and Acknowledgement

When RMR receives the table end entry (newrt|end), it will send a state message back to the Route Manager to indicate the state of the received table. The message type is 22 and the payload will contain UTF-8 tokens which indicate the state. The second token will be the table ID supplied on the start record, or the string “<id-missing>.” When the state is an error state, RMR might add a final set of tokens which contain the reason for the failure.

Upon receipt of a status message which indicates an “OK” response, the Route Manager can assume that the table has been installed and is in use. Any other response indicates that RMR did not use the table and has dropped it; the previous table is still in use.

Using A Static Route Table

A static route table can be provided to assist with testing, or to provide a bootstrap set of route information until a dynamic table is received from a routing manager. The environment variable RMR_SEED_RT is checked during RMR initialisation and if set is expected to reference a file containing a route table. This table will be loaded and used until overlaid by a table sent by the Route Manager.

For testing, the static table will be reloaded periodically if the RMR_RTG_SVC environment variable is set to -1. When this testing feature is enabled RMR will not listen for Route Manager connections, nor will it attempt to request a dynamic table.

Routing Using MEID

Starting with version 1.13.0, RMR provides the ability to select the endpoint for a message based on the MEID (managed entity ID) in the message, rather than selecting the endpoint from the round-robin list for the matching route table entry. When the MEID is used, the message is sent to the endpoint which owns, or is responsible for the managed entity. Should the owner change messages will be routed to the new owner when the route table is updated. To make use of MEID routing, there must be one or more route table entries which list the special endpoint name %meid instead of providing a round robin list. As an example, consider the following route table entry:

mse| 1000,forwarder:43086 | 10 | %meid

Figure 4: Sample route entry with the meid flag.

The final field of the entry doesn’t specify a round-robin group which means that when an application attempts to send a message with type 1000, and the subscription ID of 10, the MEID in the message will be used to select the endpoint.

MEID endpoint selection

To select an endpoint for the message based on the MEID in a message, RMR must know which endpoint owns the MEID. This information, known as an MEID map, is provided by the Route Manager over the same communication path as the route table is supplied. The following is the syntax for an MEID map.

meid_map | start | <table-id>
mme_ar | <owner-endpoint> | <meid> [<meid>...]
mme_del | <meid> [<meid>...]
meid_map | end | <count> [| <md5sum> ]

Figure 5: Meid map table.

The mme_ar records are add/update records and allow for the list of MEIDs to be associated with (owned by) the indicated endpoint. The <owner-endpoint> is the hostname:port, or IP address and port, of the application which owns the MEID and thus should receive any messages which are routed based on a route table entry with %meid as the round-robin group. The mme_del records allow for MEIDs to be deleted from RMR’s view. Finally, the <count> is the number of add/replace and delete records which were sent; if RMR does not match the <count> value to the number of records, then it will not add the data to the table. Updates only need to list the ownership changes that are necessary; in other words, the Route Manager does not need to supply all of the MEID relationships with each update.

The optional <md5sum> field on the end record should be the MD5 hash of all of the records between the start and end records. This allows for a precise verification that the transmitted data was correctly received.

If a static seed file is being used for the route table, a second section can be given which supplies the MEID map. The following is a small example of a seed file:

newrt|start | id-64306
mse|0|-1| %meid
mse|1|-1|172.19.0.2:4560
mse|2|-1|172.19.0.2:4560
mse|3|-1|172.19.0.2:4560
mse|4|-1|172.19.0.2:4560
mse|5|-1|172.19.0.2:4560
newrt|end

meid_map | start | id-028919
mme_ar| 172.19.0.2:4560 | meid000 meid001 meid002 meid003 meid004 meid005
mme_ar| 172.19.0.42:4560 | meid100 meid101 meid102 meid103
mme_del | meid1000
meid_map | end | 1

Figure 6: Illustration of both a route table and meid map in the same file.

The tables above will route all messages with a message type of 0 based on the MEID. There are 10 meids which are owned by two different endpoints. The table also deletes the MEID meid1000 from RMR’s view.

Reserved Message Types

RMR is currently reserving message types in the range of 0 through 99 (inclusive) for its own use. Please do not use these types in any production or test environment as the results may be undesired.

Appendix A – Glossary

Many terms in networking can be interpreted with multiple meanings, and several terms used in various RMR documentation are RMR specific. The following definitions are the meanings of terms used within RMR documentation and should help the reader to understand the intent of meaning.

application	A programme which uses RMR to send and/or receive messages to/from another RMR based application.
Critical error	An error that RMR has encountered which will prevent further successful processing by RMR. Critical errors usually indicate that the application should abort.
Endpoint	An RMR based application that is defined as being capable of receiving one or more types of messages (as defined by a routing key.)
Environment variable	A key/value pair which is set externally to the application, but which is available to the application (and referenced libraries) through the getenv system call. Environment variables are the main method of communicating information such as port numbers to RMR.
Error	An abnormal condition that RMR has encountered, but will not affect the overall processing by RMR, but may impact certain aspects such as the ability to communicate with a specific endpoint. Errors generally indicate that something, usually external to RMR, must be addressed.
Host name	The name of the host as returned by the gethostbyname system call. In a containerised environment this might be the container or service name depending on how the container is started. From RMR’s point of view, a host name can be used to resolve an endpoint definition in a route table.)
IP	Internet protocol. A low level transmission protocol which governs the transmission of datagrams across network boundaries.
Listen socket	A TCP socket used to await incoming connection requests. Listen sockets are defined by an interface and port number combination where the port number is unique for the interface.
Message	A series of bytes transmitted from the application to another RMR based application. A message is comprised of RMR specific data (a header), and application data (a payload).
Message buffer	A data structure used to describe a message which is to be sent or has been received. The message buffer includes the payload length, message type, message source, and other information.
Message type	A signed integer (0-32000) which identifies the type of message being transmitted, and is one of the two components of a routing key. See Subscription ID.
Payload	The portion of a message which holds the user data to be transmitted to the remote endpoint. The payload contents are completely application defined.
RMR context	A set of information which defines the current state of the underlying transport connections that RMR is managing. The application will be give a context reference (pointer) that is supplied to most RMR functions as the first parameter.
Round robin	The method of selecting an endpoint from a list such that all endpoints are selected before starting at the head of the list.
Route table	A series of “rules” which define the possible endpoints for each routing key.
Route table manager	An application responsible for building a route table and then distributing it to all applicable RMR based applications.
Routing	The process of selecting an endpoint which will be the recipient of a message.
Routing key	A combination of message type and subscription ID which RMR uses to select the destination endpoint when sending a message.
Source	The sender of a message.
Subscription ID	A signed integer value (0-32000) which identifies the subscription characteristic of a message. It is used in conjunction with the message type to determine the routing key.
Target	The endpoint selected to receive a message.
TCP	Transmission Control Protocol. A connection based internet protocol which provides for lossless packet transportation, usually over IP.
Thread	Also called a process thread, or pthread. This is a lightweight process which executes in concurrently with the application and shares the same address space. RMR uses threads to manage asynchronous functions such as route table updates.
Trace information	An optional portion of the message buffer that the application may populate with data that allows for tracing the progress of the transaction or application activity across components. RMR makes no use of this data.
Transaction ID	A fixed number of bytes in the message buffer) which the application may populate with information related to the transaction. RMR makes use of the transaction ID for matching response messages with the &c function is used to send a message.
Transient failure	An error state that is believed to be short lived and that the operation, if retried by the application, might be successful. C programmers will recognise this as EAGAIN.
Warning	A warning occurs when RMR has encountered something that it believes isn’t correct, but has a defined work round.
Wormhole	A direct connection managed by RMR between the user application and a remote, RMR based, application.

RIC Message Types

Overview

RMR routes messages based on a combination of message type and subscription ID both of which are integers. The message type constants are defined in the RIC_msg_types.h header file included with the RMR development package while subscription IDs are generated by the subscription manager process at run-time. This document does not include the constant values to avoid incorrectly propagating a stale value through the reference of an outdated document.

Non-Routable Message Types

These message types are not routable and a message passed to an RMR function with any of these constants set will not be sent.

RIC_UNDEFINED

Message type is unset or undefined. Newly allocated messages have the type value set to this constant.

RMR Reserved Message Types

These message types are reserved for RMR communications (e.g. with Route Manager).

RMRRM_TABLE_DATA	Table data from route manger. Route manager sends all route mse, etc.) with this type.
RMRRM_REQ_TABLE	Request for table update. RMR will send a message with this a table update from route manger.
RMRRM_TABLE_STATE	This message type conveys the state of the route table to the end of a table is noticed.

System Support Message Types

These message types are used for systems level communications such as health checks, alarms and probes.

RIC_HEALTH_CHECK_REQ	When received the application is expected to return a response to the current “health” of the application.
RIC_HEALTH_CHECK_RESP	Health responses are sent with a message of this type.
RIC_ALARM	Alarm messages with this type are routed to the alarm collection process.
RIC_ALARM_QUERY	Unknown meaning
RIC_METRICS	This message type causes the message to be routed to the xAPP responsible redistributing metrics.

Unclassified Message Types

The following message types have not been clasified into a specific category.

RIC_SCTP_CONNECTION_FAILURE
RIC_SCTP_CLEAR_ALL
E2_TERM_INIT
E2_TERM_KEEP_ALIVE_REQ
E2_TERM_KEEP_ALIVE_RESP
RAN_CONNECTED
RAN_RESTARTED
RAN_RECONFIGURED
RIC_ENB_LOAD_INFORMATION
RIC_ERROR_INDICATION
RIC_SN_STATUS_TRANSFER
RIC_UE_CONTEXT_RELEASE
RIC_X2_SETUP_REQ
RIC_X2_SETUP_RESP
RIC_X2_SETUP_FAILURE
RIC_X2_RESET
RIC_X2_RESET_RESP
RIC_ENB_CONF_UPDATE
RIC_ENB_CONF_UPDATE_ACK
RIC_ENB_CONF_UPDATE_FAILURE
RIC_RES_STATUS_REQ
RIC_RES_STATUS_RESP
RIC_RES_STATUS_FAILURE
RIC_RESOURCE_STATUS_UPDATE
RIC_SGNB_ADDITION_REQ
RIC_SGNB_ADDITION_ACK
RIC_SGNB_ADDITION_REJECT
RIC_SGNB_RECONF_COMPLETE
RIC_SGNB_MOD_REQUEST
RIC_SGNB_MOD_REQUEST_ACK
RIC_SGNB_MOD_REQUEST_REJ
RIC_SGNB_MOD_REQUIRED
RIC_SGNB_MOD_CONFIRM
RIC_SGNB_MOD_REFUSE
RIC_SGNB_RELEASE_REQUEST
RIC_SGNB_RELEASE_REQUEST_ACK
RIC_SGNB_RELEASE_REQUIRED
RIC_SGNB_RELEASE_CONFIRM
RIC_RRC_TRANSFER
RIC_ENDC_X2_SETUP_REQ
RIC_ENDC_X2_SETUP_RESP
RIC_ENDC_X2_SETUP_FAILURE
RIC_ENDC_CONF_UPDATE
RIC_ENDC_CONF_UPDATE_ACK
RIC_ENDC_CONF_UPDATE_FAILURE
RIC_SECONDARY_RAT_DATA_USAGE_REPORT
RIC_GNB_STATUS_INDICATION
RIC_E2_SETUP_REQ
RIC_E2_SETUP_RESP
RIC_E2_SETUP_FAILURE
RIC_E2_RESET_REQ
RIC_E2_RESET_RESP
RIC_E2_RAN_ERROR_INDICATION
RIC_E2_RIC_ERROR_INDICATION
RAN_E2_RESET_REQ
RAN_E2_RESET_RESP
RIC_SUB_REQ
RIC_SUB_RESP
RIC_SUB_FAILURE
RIC_SUB_DEL_REQ
RIC_SUB_DEL_RESP
RIC_SUB_DEL_FAILURE
RIC_SERVICE_UPDATE
RIC_SERVICE_UPDATE_ACK
RIC_SERVICE_UPDATE_FAILURE
RIC_CONTROL_REQ
RIC_CONTROL_ACK
RIC_CONTROL_FAILURE
RIC_INDICATION
RIC_SERVICE_QUERY
DC_ADM_INT_CONTROL
DC_ADM_INT_CONTROL_ACK
DC_ADM_GET_POLICY
DC_ADM_GET_POLICY_ACK
A1_POLICY_REQ
A1_POLICY_RESP
A1_POLICY_QUERY
TS_UE_LIST
TS_QOE_PRED_REQ
TS_QOE_PREDICTION
TS_ANOMALY_UPDATE
TS_ANOMALY_ACK
MC_REPORT
DCAPTERM_RTPM_RMR_MSGTYPE
DCAPTERM_GEO_RMR_MSGTYPE
RIC_X2_SETUP	deprecated
RIC_X2_RESPONSE	deprecated
RIC_X2_RESOURCE_STATUS_REQUEST	deprecated
RIC_X2_RESOURCE_STATUS_RESPONSE	deprecated
RIC_X2_LOAD_INFORMATION	deprecated
RIC_E2_TERMINATION_HC_REQUEST	deprecated
RIC_E2_TERMINATION_HC_RESPONSE	deprecated
RIC_E2_MANAGER_HC_REQUEST	deprecated
RIC_E2_MANAGER_HC_RESPONSE	deprecated
RIC_CONTROL_XAPP_CONFIG_REQUEST	deprecated
RIC_CONTROL_XAPP_CONFIG_RESPONSE	deprecated

RMR Release Notes

RMR Release Notes

The following is a list of release highlights for the RMR library. At one point in time the RMR repo also housed a wrapper library with a separate version and release cycle. This resulted in leap frogging versions for each package; the RMR core library was assigned odd major numbers (e.g. 3.1.0). When the wrapper code was moved to a different repo the need to leap frog versions ceased, and beginning with version 4.0.0, the RMR versions should no longer skip.

2021 January21; Version 4.5.2

Fixes the excessive TCP session bug when sending to a slow receiver and a related segment fault because of too many open file descriptors. (RIC-735)

2021 January 19; Version 4.5.1

Version bump to work round a CI job bug preventing push of the 4.5.0 packages from staging to release in package cloud. (RIC-732)

2021 January 8; Version 4.5.0

Version bump for next release tracking. Corrected a potential locking issue in message allocation. (RIC-732)

Cherry Release

2020 December 4; Version 4.4.6

Correct a range check bug when cloning a route table in prep to load a new one. (RIC-720)

2020 November 17; Version 4.4.5

Correct bug in round robin group allocation that could lead to an empty group. (RIC-695)

2020 November 13; Version 4.4.4

Correct address memory leak in the RTE cleanup. (RIC-674)

2020 November 4; Version 4.4.3

Correct bug introduced with race fix (4.4.0) (RIC-674)

2020 November 4; Version 4.4.2

Changes to correct more complaints generated by a code scan. (RIC-673) Also addressed some sonar coverage issues with unit test changes.

2020 November 4; Version 4.4.1

Changes to correct complaints generated by a code scan. (RIC-673)

2020 November 4; Version 4.4.0

Changes to address a potential race condition when route tables arrive in quick succession. (RIC-674)

2020 October 30; Version 4.3.1

Changes to address code analyser scans and two bug fixes identified while addressing the analysis data. (RIC-673)

2020 October 2; Version 4.3.0

Add message types for traffic steering anomaly messages

2020 September 15; Version 4.2.4

Add man page for the rmr_set_low_latency() function (RIC-631)

2020 September 15; Version 4.2.3

Correct arg processing bug in rmr_rpobe (RIC-645)

2020 August 4; Version 4.2.2

Correct bug in the rmr_probe support utility when -r option is used on the command line (RIC-644)

2020 August 4; Version 4.2.1

Add additional environment variable dump if RMR_LOG_VLEVEL set to 4 at start.

2020 August 3; Version 4.2.0

Add support for the RMR_RTREQ_FREQ environment variable to control the request frequency for a new route table (default 5s if not supplied). (RIC-630)

2020 July 21; Version 4.1.4

Fix bug in SI95 – possible use of pointer after free (RIC-626).

2020 July 9; version 4.1.3

Allow RTS messages to be sent before the arrival of the initial route table. Calls to RTS (heart beat responses) prior to the initial route table load could cause a crash if a framework blindly assumes that RTS is valid. (RIC-589)

2020 June 22; version 4.1.2

Fix typo in RIC Message header file.

Add document for message type constants and the scripts which generate them.

2020 June 22; version 4.1.1

Add new message types to RIC header file for

RIC_ALARM (110) RIC_ALARM_QUERY (111) RIC_METRICS (120) RAN_E2_RESET_REQ (12008) RAN_E2_RESET_RESP (12009)

2020 June 18; version 4.1.0

Bump version minor to move away from 4.0.* which will bump for any patches applied back to bronze.

Add magic C++ goo to symtab header file allowing C++ xAPPs to use the symbol table directly.

Bronze Release

2020 May 06; version 4.0.5

Fix the bug in SI95 receive message management semaphore count issue. (RIC-355)

2020 April 29; version 4.0.4

Fix the traffic steering message type constants (again) (RIC-342)

2020 April 28; version 4.0.3

Fix sonar flagged bugs (RIC-78)

2020 April 24; version 4.0.2

Correct bug in SI95 transport header length validation (RIC-341)

2020 April 22; version 4.0.1

Correct message type constant for Traffic Steering predication (RIC-342)

2020 April 21; version 4.0.0

The NNG based libraries are no longer included in the RMR packages. This is considered a breaking change as NNG will not be supported by default. It is still possible to build with RMR-NNG libraries, but that is the exception. The API between 3.8.2 and 4.0.0 is the SAME. Upgrading to 4.0.0 only means that the underlying transport mechanism is limited only to SI95.

The rmr_rcv_specific() function has been deprecated as it was necessary only for NNG and Nanomsg support. Its use should be discontinued.

2020 April 20; version 3.8.2

Fix bug which was preventing an instance receiving dynamic route table updates. (RIC-336)

2020 April 20; version 3.8.1

Add user guide which replaces the concatenation of man pages (RIC-328)

2020 April 17; version 3.8.0

Add safe connect to avoid potential connect bug on Linux (RIC-332)

Change debugging in route table collector to avoid possible segment fault when in level 2 debug (RIC-335)

2020 April 15; version 3.7.4

Add missing message type to header file (RIC-334)

2020 April 14; version 3.7.3

Fix bug in rmr_call() when using SI95 (RIC-333)

2020 April 10; version 3.7.2

Fix bug related to static route table only mode (RIC-331)

2020 April 9; version 3.7.1

The max length restriction for receiving messages when using SI95 has been removed. The length supplied during initialisation is used as the “normal maximum” and default buffer allocation size, but messages arriving which are larger are accepted. (RIC-309)

2020 April 7; version 3.7.0

The health check support programme was renamed to rmr_probe (RIC-308).

2020 April 6; version 3.6.6

Correct bug in SI95 address conversion module (RIC-327) Correct bug in SI initialisation module

2020 April 2; version 3.6.5

Correct potential nil pointer use when examining interfaces for use as a listen target (RIC-307)

2020 April 1; version 3.6.4

Correct potential nil pointer use in the NNG interface (RIC-303) Correct issue preventing CI build without a container

2020 March 30; version 3.6.3

Correct the max receive message size constant in rmr.h (RIC-301)

2020 March 23; version 3.6.2

Fix message initialisation bug when pulling a message from the pool (RIC-295)

2020 March 19; version 3.6.1

Fix problem with RPM package install

2020 March 18; version 3.6.0

Add message types to support traffic steering

2020 March 16; version 3.5.2

Correct bug in the meid table parser that prevented the ack/nack of meid tables (RIC-273)

2020 March 10; version 3.5.1

Add missing health check message types.

2020 March 9; version 3.5.0

Added new wormhole send function: rmr_wh_call().

2020 March 6; version 3.4.0

Add new wormhole state function: rmr_wh_state().

2020 March 5; Version 3.3.1

Correct several “bugs” identified by automatic code analysis.

2020 March 4; Version 3.3.0

Add SI95 based unit testing Health check support binary added (reason for minor bump)

2020 February 26; version 3.2.5

Fix source address bug in SI95 receive/send funcitons. Fix threading issues involving session disconnection in SI95 Remove unused SI95 status variable.

2020 February 24; version 3.2.4

Fix meid bug (RIC-220) causing core dump.

2020 February 21; version 3.2.3

Add meid routing support to the SI95 interface.

2020 February 20; version 3.2.2

Fix receive thread related core dump (ring early unlock).

2020 February 19; version 3.2.1

Added missing message types (E2-Setup)

2020 February 18; version 3.2.0

Added support for new Route Manager and it’s ability to accept a request for table update.

2020 February 14; version 3.1.3

Fix bug in SIsend which was causing a core dump in some cases where the application attempted to send on a connection that had disconnected. (RIC-207).

2020 February 6; version 3.1.2

Fix disconnection detection bug in interface to SI95.

2020 January 31; verison 3.1.1

Allow route table thread logging to be completely disabled when logging is turned off.

2020 January 26; verison 3.1.0

First step to allowing the user programme to control messages written to standard error. Introduces the rmr_set_vlevel() function, and related environment variable.

2020 January 24; verison 3.0.5

Fix bug in SI95 with receive buffer allocation.

2020 January 23; verison 3.0.4

Fix bug in SI95 causing excessive CPU usage on poll.

2020 January 22; verison 3.0.3

Enable thread support for multiple receive threads.

2020 January 21; verison 3.0.2

Fix bug in SI95 (missing reallocate payload function).

2020 January 20; verison 3.0.1

Enable support for dynamic route table updates via RMR session.

2020 January 16; version 3.0.0

Introduce support for SI95 transport library to replace NNG. (RMR library versions will use leading odd numbers to avoid tag collisions with the wrapper tags which will use even numbers.)

2019 December 9; version 1.13.1

Correct documentation and missing rel-notes update for RTD.

2019 December 6; version 1.13.0

Add ability to route messages based on the MEID in a message combined with the message type/subscription-ID.

Amber Release

2019 November 14; version 1.11.1

Fix bug in payload reallocation function; correct length of payload was not always copied.

2019 November 13; version 1.12.1

New message type constants added to support A1.

2019 November 4; version 1.11.0

Version bump to move away from the 1.10.* to distinguish between release A and the trial.

2019 November 7; version 1.12.0

Version cut to support continued development for next release preserving the 1.11.* versions for release 1 (Amber) and related fixes.

2019 October 31; version 1.10.2

Provide the means to increase the payload size of a received message without losing the data needed to use the rmr_rts_msg() funciton.

2019 October 21; version 1.10.1

Fix to prevent null message buffer from being returned by the timeout receive function if the function is passed one to reuse.

2019 October 21; version 1.10.1

Add periodic dump of send count info to stderr.

2019 September 27; version 1.9.0

Python bindings added receive all queued function and corrected a unit test

2019 September 25; version 1.8.3

Correct application level test issue causing timing problems during jenkins verification testing at command and merge

Handle the NNG connection shutdown status which may now be generated when a connection throug a proxy is reset.

2019 September 25; version 1.8.2

Correct bug in rmr_torcv_msg() when timeout set to zero (0).

2019 September 19; version 1.8.1

Correct missing constant for wrappers.

2019 September 19; version 1.8.0

New message types added:

RAN_CONNECTED, RAN_RESTARTED, RAN_RECONFIGURED

2019 September 17; version 1.7.0

Initial connection mode now defaults to asynchronous. Set RMR_ASYNC_CONN=0 in the environment before rmr_init() is invoked to revert to synchronous first TCP connections. (Recovery connection attempts have always been asynchronous).

2019 September 3; version 1.6.0

Fix bug in the rmr_rts_msg() function. If a return to sender message failed, the source IP address was not correctly adjusted and could cause the message to be “reflected” back to the sender on a retry.

Added the ability to set the source “ID” via an environment var (RMR_SRC_ID). When present in the environment, the string will be placed in to the message header as the source and thus be used by an application calling rmr_rts_smg() to return a response to the sender. If this environment variable is not present, the host name (original behaviour) is used.

2019 August 26; version 1.4.0

New message types were added.

2019 August 16; version 1.3.0

New mesage types added.

2019 August 13; version 1.2.0 (API change, non-breaking)

The function rmr_get_xact() was added to proide a convenient way to extract the transaction field from a message.

2019 August 8; version 1.1.0 (API change)

This change should be backward compatable/non-breaking A new field has been added to the message buffer (rmr_mbuf_t). This field (tp_state) is used to communicate the errno value that the transport mechanism might set during send and/or receive operations. C programmes should continue to use errno directly, but in some environments wrappers may not be able to access errno and this provides the value to them. See the rmr_alloc_msg manual page for more details.

2019 August 6; version 1.0.45 (build changes)

Support for the Nanomsg transport library has been dropped.

The library librmr.* will no longer be included in packages.

Packages will install RMR libraries into the system preferred

target directory. On some systems this is /usr/local/lib and on others it is /usr/local/lib64. The diretory is determined by the sytem on which the package is built and NOT by the system installing the package, so it’s possible that the RMR libraries end up in a strange location if the .deb or .rpm file was generated on a Linux flavour that has a different preference than the one where the package is installed.

2019 August 6; version 1.0.44 (API change)

Added a new message type constant.

2019 July 15; Version 1.0.39 (bug fix)

Prevent unnecessary usleep in retry loop.

2019 July 12; Version 1.0.38 (API change)

Added new message types to RIC_message_types.h.

2019 July 11; Version 1.0.37

librmr and librmr_nng

• Add message buffer API function rmr_trace_ref() (see rmr_trace_ref.3 manual page in dev package).

2020 April 8; Version n/a

RMR Python moved to Python Xapp Framework (https://gerrit.o-ran-sc.org/r/admin/repos/ric-plt/xapp-frame-py)

2020 February 29; Version 2.4.0

Add consolidated testing under CMake Add support binary for health check (SI95 only)

2020 February 28; Version 2.3.6

Fix bug in Rt. Mgr comm which prevented table ID from being sent on ack message (RIC-232).

Man Page: rmr

RMR LIBRARY

NAME

RMR – Ric Message Router Library

DESCRIPTION

RMR is a library which provides a user application with the ability to send and receive messages to/from other RMR based applications without having to understand the underlying messaging transport environment (e.g., SI95) and without needing to know which other endpoint applications are currently available and accepting messages. To do this, RMR depends on a routing table generated by an external source. This table is used to determine the destination endpoint of each message sent by mapping the message type T (supplied by the user application) to an endpoint entry. Once determined, the message is sent directly to the endpoint. The user application is unaware of which endpoint actually receives the message, and in some cases whether that message was sent to multiple applications.

RMR functions do provide for the ability to respond to the specific source instance of a message allowing for either a request response, or call response relationship when needed.

The Route Table

The library must be given a route table which maps message types (integers) to endpoint groups such that each time a message of type T is sent, the message is delivered to one member of each group associated with T. For example, message type 2 might route to two different groups where group A has two members, worker1 and worker2, while group B has only one member, logger1.

The route table consists of a start record, one or more table entry records, and an end record. All table records contain fields separated with vertical bars (|), and allow for trailing comments with the standard shell comment symbol (hash, #) provided that the start of the comment is separated from the last token on the record by one or more spaces. Leading and trailing white space in each field is ignored. The route table supports two entry types: rte and mse.

A rte entry defines a message type, an optional sender application, and the endpoint(s) which accept the indicated message type. However, this format is deprecated and may be removed in a future version. An example record appears next.

rte | 1 | app10:4560

The second type of entry is mse. This entry defines a message type, an optional sender application, a subscription ID, and a collection of endpoints. An example record appears next.

mse | 1000,forwarder:43086 | 10 | app2:43086

It is the responsibility of the route table generator to know which endpoints belong to which groups, and which groups accept which message types. Once understood, the route table generator publishes a table that is ingested by RMR and used for mapping messages to end points.

The following is a simple route table which causes message types 0 through 9 to be routed to specific applications:

newrt|start
   mse|0|-1| %meid
   mse|1|-1|app10:4560,app11:4560
   mse|2|-1|app12:4560
   mse|3|-1|app14:4560
   mse|4|-1|app18:4560
   mse|5|-1|app01:4560
   mse|6|-1|app02:4560
   mse|7|-1|app03:4560
   mse|8|-1|app04:4560
   mse|9|-1|app05:4560
newrt|end

The special endpoint “%meid” indicates that the message type (0 in this case) is to be routed to the endpoint which has been listed as the “owner” for the meid appearing in the message. MEID ownership is communicated to RMR using the same Route Table Manager interface and by supplying a “table” such as the one below:

meid_map | start
   mme_ar | control1 | meid000 meid001 meid002 meid003 meid004 meid005
   mme_ar | control2 | meid100 meid101 meid102 meid103
meid_map | end | 2

This table indicates that the application (endpoint) control1 “owns” 6 MEIDs and control2 owns 4. When message type 0 is sent, the MEID in the message will be used to select the endpoint via this table.

The MEID table will update the existing owner relationships, and add new ones; it is necessary to send only the changes with the add/replace (mme_ar) entries in the table. When necessary, MEIDs can be deleted by adding an mme_del record to the table. The following example illustrates how this might look:

meid_map | start
   mme_ar | control1 | meid000 meid001 meid002 meid003 meid004 meid005
   mme_ar | control2 | meid100 meid101 meid102 meid103
   mme_del| meid200 meid401
meid_map | end | 3

Route Table Syntax

The following illustrates the syntax for both types of route table entries.

newrt | start
rte | <message-type>[,<sender-endpoint>] | <round-robin-grp>[;<round-robin-grp>]...
mse | <message-type>[,<sender-endpoint>] | <sub-id> | <round-robin-grp>[;<round-robin-grp>]...
newrt | end

A round robin group is one or more endpoints from which one will be selected to receive the message. When multiple endpoints are given in a group, they must be separated with a comma. An endpoint is an IP address and port (e.g. 192.158.4.30:8219), or DNS name and port, of the application that should receive the message type. If multiple round-robin groups are given, they must be separated by a semicolon.

MEID Map Syntax

The MEID map is similar to the route table. Entries are used to add or replace the ownership of one or more MEIDs (mme_ar) or to delete one or more MEIDs (mme_del). The following is the syntax for the MEID map.

meid_map | start
mme_ar | <owner-endpoint> | <meid> [<meid>...]
mme_del | <meid> [<meid>...]
meid_map | end | <count> | <md5sum>

The <count> on the end record indicates the number of mme_ar and mme_del records which were sent; if the count does not match the whole map is refused and dropped. The <owner-endpoint> is the endpoint which should receive the message when a message is routed based on the MEID it contains. A MEID may be “owned” by only one endpoint, and if supplied multiple times, the last observed relationship is used. Each of the lists of MEIDs are blank separated.

The optional <md5sum> on the end record should be the computed MD5 hash for all records which appear between the start and and records. This allows for a tighter verification that all data was received exactly as the route manager transmitted them.

Environment

To enable configuration of the library behaviour outside of direct user application control, RMR supports a number of environment variables which provide information to the library. The following is a list of the various environment variables, what they control and the defaults which RMR uses if undefined.

RMR_ASYNC_CONN	Allows the async connection mode to be turned off (by setting the value to 0). When set to 1, or missing from the environment, RMR will invoke the connection interface in the transport mechanism using the non-blocking (async) mode. This will likely result in many “soft failures” (retry) until the connection is established, but allows the application to continue unimpeded should the connection be slow to set up.
RMR_BIND_IF	This provides the interface that RMR will bind listen ports to, allowing for a single interface to be used rather than listening across all interfaces. This should be the IP address assigned to the interface that RMR should listen on, and if not defined RMR will listen on all interfaces.
RMR_CTL_PORT	This variable defines the port that RMR should open for communications with Route Manager, and other RMR control applications. If not defined, the port 4561 is assumed. Previously, the RMR_RTG_SVC (route table generator service port) was used to define this port. However, a future version of Route Manager will require RMR to connect and request tables, thus that variable is now used to supply the Route Manager’s well-known address and port. To maintain backwards compatibility with the older Route Manager versions, the presence of this variable in the environment will shift RMR’s behaviour with respect to the default value used when RMR_RTG_SVC is not defined. When RMR_CTL_PORT is defined: RMR assumes that Route Manager requires RMR to connect and request table updates is made, and the default well-known address for Route manager is used (routemgr:4561). When RMR_CTL_PORT is undefined: RMR assumes that Route Manager will connect and push table updates, thus the default listen port (4561) is used. To avoid any possible misinterpretation and/or incorrect assumptions on the part of RMR, it is recommended that both the RMR_CTL_PORT and RMR_RTG_SVC be defined. In the case where both variables are defined, RMR will behave exactly as is communicated with the variable’s values.
RMR_RTREQ_FREQ	When RMR needs a new route table it will send a request once every n seconds. The default value for n is 5, but can be changed if this variable is set prior to invoking the process. Accepted values are between 1 and 300 inclusive.
RMR_RTG_SVC	The value of this variable depends on the Route Manager in use. When the Route Manager is expecting to connect to an xAPP and push route tables, this variable must indicate the port which RMR should use to listen for these connections. When the Route Manager is expecting RMR to connect and request a table update during initialisation, the variable should be the host of the Route Manager process. The RMR_CTL_PORT variable (added with the support of sending table update requests to Route manager), controls the behaviour if this variable is not set. See the description of that variable for details.
RMR_HR_LOG	By default RMR writes messages to standard error (incorrectly referred to as log messages) in human readable format. If this environment variable is set to 0, the format of standard error messages might be written in some format not easily read by humans. If missing, a value of 1 is assumed.
RMR_LOG_VLEVEL	This is a numeric value which corresponds to the verbosity level used to limit messages written to standard error. The lower the number the less chatty RMR functions are during execution. The following is the current relationship between the value set on this variable and the messages written: 0 Off; no messages of any sort are written. 1 Only critical messages are written (default if this variable does not exist) 2 Errors and all messages written with a lower value. 3 Warnings and all messages written with a lower value. 4 Informational and all messages written with a lower value. 5 Debugging mode – all messages written, however this requires RMR to have been compiled with debugging support enabled.
RMR_RTG_ISRAW	Deprecated. Should be set to 1 if the route table generator is sending “plain” messages (not using RMR to send messages), 0 if the RTG is using RMR to send. The default is 1 as we don’t expect the RTG to use RMR. This variable is only recognised when using the NNG transport library as it is not possible to support NNG “raw” communications with other transport libraries. It is also necessary to match the value of this variable with the capabilities of the Route Manager; at some point in the future RMR will assume that all Route Manager messages will arrive via an RMR connection and will ignore this variable.
RMR_SEED_RT	This is used to supply a static route table which can be used for debugging, testing, or if no route table generator process is being used to supply the route table. If not defined, no static table is used and RMR will not report ready until a table is received. The static route table may contain both the route table (between newrt start and end records), and the MEID map (between meid_map start and end records).
RMR_SRC_ID	This is either the name or IP address which is placed into outbound messages as the message source. This will used when an RMR based application uses the rmr_rts_msg() function to return a response to the sender. If not supplied RMR will use the hostname which in some container environments might not be routable. The value of this variable is also used for Route Manager messages which are sent via an RMR connection.
RMR_VCTL_FILE	This supplies the name of a verbosity control file. The core RMR functions do not produce messages unless there is a critical failure. However, the route table collection thread, not a part of the main message processing component, can write additional messages to standard error. If this variable is set, RMR will extract the verbosity level for these messages (0 is silent) from the first line of the file. Changes to the file are detected and thus the level can be changed dynamically, however RMR will only suss out this variable during initialisation, so it is impossible to enable verbosity after startup.
RMR_WARNINGS	If set to 1, RMR will write some warnings which are non-performance impacting. If the variable is not defined, or set to 0, RMR will not write these additional warnings.

SEE ALSO

rmr_alloc_msg(3), rmr_tralloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_init_trace(3), rmr_get_meid(3), rmr_get_src(3), rmr_get_srcip(3), rmr_get_trace(3), rmr_get_trlen(3), rmr_get_xact(3), rmr_payload_size(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_realloc_payload(3), rmr_ring_free(3), rmr_set_trace(3), rmr_torcv_msg(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_alloc_msg

RMR LIBRARY FUNCTIONS

NAME

rmr_alloc_msg

SYNOPSIS

#include <rmr/rmr.h>

rmr_mbuf_t* rmr_alloc_msg( void* ctx, int size );

DESCRIPTION

The rmr_alloc_msg function is used to allocate a buffer which the user programme can write into and then send through the RMR library. The buffer is allocated such that sending it requires no additional copying out of the buffer. If the value passed in size is less than or equal to 0, then the normal maximum size supplied on the rmr_init call will be used. When size is greater than zero, the message allocated will have at least the indicated number of bytes in the payload. There is no maximum size imposed by RMR, however the underlying system memory management (e.g. malloc) functions may impose a limit.

The ctx parameter is the void context pointer that was returned by the rmr_init function.

The pointer to the message buffer returned is a structure which has some user application visible fields; the structure is described in rmr.h, and is illustrated below.

typedef struct {
    int state;
    int mtype;
    int len;
    unsigned char* payload;
    unsigned char* xaction;
    int sub_id;
    int tp_state;
} rmr_mbuf_t;

Where:

state	Is the current buffer state. Following a call to rmr_send_msg the state indicates whether the buffer was successfully sent which determines exactly what the payload points to. If the send failed, the payload referenced by the buffer is the message that failed to send (allowing the application to attempt a retransmission). When the state is RMR_OK the buffer represents an empty buffer that the application may fill in in preparation to send.
mtype	When sending a message, the application is expected to set this field to the appropriate message type value (as determined by the user programme). Upon send this value determines how the RMR library will route the message. For a buffer which has been received, this field will contain the message type that was set by the sending application.
len	The application using a buffer to send a message is expected to set the length value to the actual number of bytes that it placed into the message. This is likely less than the total number of bytes that the message can carry. For a message buffer that is passed to the application as the result of a receive call, this will be the value that the sending application supplied and should indicate the number of bytes in the payload which are valid.
payload	The payload is a pointer to the actual received data. The user programme may read and write from/to the memory referenced by the payload up until the point in time that the buffer is used on a rmr_send, rmr_call or rmr_reply function call. Once the buffer has been passed back to a RMR library function the user programme should NOT make use of the payload pointer.
xaction	The xaction field is a pointer to a fixed sized area in the message into which the user may write a transaction ID. The ID is optional with the exception of when the user application uses the rmr_call function to send a message and wait for the reply; the underlying RMR processing expects that the matching reply message will also contain the same data in the xaction field.
sub_id	This value is the subscription ID. It, in combination with the message type is used by rmr to determine the target endpoint when sending a message. If the application to application protocol does not warrant the use of a subscription ID, the RMR constant RMR_VOID_SUBID should be placed in this field. When an application is forwarding or returning a buffer to the sender, it is the application’s responsibility to set/reset this value.
tp_state	For C applications making use of RMR, the state of a transport based failure will often be available via errno. However, some wrapper environments may not have direct access to the C-lib errno value. RMR send and receive operations will place the current value of errno into this field which should make it available to wrapper functions. User applications are strongly cautioned against relying on the value of errno as some transport mechanisms may not set this value on all calls. This value should also be ignored any time the message status is RMR_OK.

RETURN VALUE

The function returns a pointer to a rmr_mbuf structure, or NULL on error.

ERRORS

ENOMEM

Unable to allocate memory.

SEE ALSO

rmr_tralloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_init_trace(3), rmr_get_trace(3), rmr_get_trlen(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_set_trace(3)

Man Page: rmr_bytes2meid

RMR LIBRARY FUNCTIONS

NAME

rmr_bytes2meid

SYNOPSIS

#include <rmr/rmr.h>

int rmr_bytes2meid( rmr_mbuf_t* mbuf, unsigned char* src, int len )

DESCRIPTION

The rmr_bytes2meid function will copy up to len bytes from src to the managed entity ID (meid) field in the message. The field is a fixed length, gated by the constant RMR_MAX_MEID and if len is larger than this value, only RMR_MAX_MEID bytes will actually be copied.

RETURN VALUE

On success, the actual number of bytes copied is returned, or -1 to indicate a hard error. If the length is less than 0, or not the same as length passed in, errno is set to one of the errors described in the Errors section.

ERRORS

If the returned length does not match the length passed in, errno will be set to one of the following constants with the meaning listed below.

EINVAL	The message, or an internal portion of the message, was corrupted or the pointer was invalid.
EOVERFLOW	The length passed in was larger than the maximum length of the field; only a portion of the source bytes were copied.

EXAMPLE

SEE ALSO

rmr_alloc_msg(3), rmr_bytes2xact(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_get_meid(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_str2xact(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_bytes2payload

RMR LIBRARY FUNCTIONS

NAME

rmr_bytes2payload

SYNOPSIS

#include <rmr/rmr.h>

void rmr_bytes2payload( rmr_mbuf_t* mbuf, unsigned char* src, int len )

DESCRIPTION

This is a convenience function as some wrapper languages might not have the ability to directly copy into the payload buffer. The bytes from src for the length given are copied to the payload. It is the caller’s responsibility to ensure that the payload is large enough. Upon successfully copy, the len field in the message buffer is updated to reflect the number of bytes copied.

There is little error checking, and no error reporting.

RETURN VALUE

None.

EXAMPLE

SEE ALSO

rmr_alloc_msg(3), rmr_bytes2xact(3), rmr_bytes2payload(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_get_meid(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_str2xact(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_bytes2xact

RMR LIBRARY FUNCTIONS

NAME

rmr_bytes2xact

SYNOPSIS

#include <rmr/rmr.h>

int rmr_bytes2xact( rmr_mbuf_t* mbuf, unsigned char* src, int len )

DESCRIPTION

The rmr_bytes2xact function will copy up to len bytes from src to the transaction ID (xaction) field in the message. The field is a fixed length, gated by the constant RMR_MAX_XID and if len is larger than this value, only RMR_MAX_XID bytes will actually be copied.

RETURN VALUE

On success, the actual number of bytes copied is returned, or -1 to indicate a hard error. If the length is less than 0, or not the same as length passed in, errno is set to one of the errors described in the Errors section.

ERRORS

If the returned length does not match the length passed in, errno will be set to one of the following constants with the meaning listed below.

EINVAL	The message, or an internal portion of the message, was corrupted or the pointer was invalid.
EOVERFLOW	The length passed in was larger than the maximum length of the field; only a portion of the source bytes were copied.

EXAMPLE

SEE ALSO

rmr_alloc_msg(3), rmr_bytes2meid(3), rmr_call(3), rmr_free_msg(3), rmr_get_meid(3), rmr_get_rcvfd(3), rmr_get_xact(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_call

RMR LIBRARY FUNCTIONS

NAME

rmr_call

SYNOPSIS

#include <rmr/rmr.h>

extern rmr_mbuf_t* rmr_call( void* vctx, rmr_mbuf_t* msg );

DESCRIPTION

The rmr_call function sends the user application message to a remote endpoint, and waits for a corresponding response message before returning control to the user application. The user application supplies a completed message buffer, as it would for a rmr_send call, but unlike with the send, the buffer returned will have the response from the application that received the message.

Messages which are received while waiting for the response are queued internally by RMR, and are returned to the user application when rmr_rcv_msg is invoked. These messages are returned in the order received, one per call to rmr_rcv_msg.

Call Timeout

The rmr_call function implements a timeout failsafe to prevent, in most cases, the function from blocking forever. The timeout period is not based on time (calls to clock are deemed too expensive for a low latency system level library), but instead the period is based on the number of received messages which are not the response. Using a mechanism which is not time based for timeout prevents the async queue from filling (which would lead to message drops) in an environment where there is heavy message traffic.

When the threshold number of messages have been queued without receiving a response message, control is returned to the user application and a nil pointer is returned to indicate that no message was received to process. Currently the threshold is fixed at 20 messages, though in future versions of the library this might be extended to be a parameter which the user application may set.

Retries

The send operations in RMR will retry soft send failures until one of three conditions occurs:

• The message is sent without error

• The underlying transport reports a hard failure

• The maximum number of retry loops has been attempted

A retry loop consists of approximately 1000 send attempts without any intervening calls to sleep() or usleep(). The number of retry loops defaults to 1, thus a maximum of 1000 send attempts is performed before returning to the user application. This value can be set at any point after RMR initialisation using the rmr_set_stimeout() function allowing the user application to completely disable retires (set to 0), or to increase the number of retry loops.

Transport Level Blocking

The underlying transport mechanism used to send messages is configured in non-blocking mode. This means that if a message cannot be sent immediately the transport mechanism will not pause with the assumption that the inability to send will clear quickly (within a few milliseconds). This means that when the retry loop is completely disabled (set to 0), that the failure to accept a message for sending by the underlying mechanisms (software or hardware) will be reported immediately to the user application.

It should be noted that depending on the underlying transport mechanism being used, it is extremely likely that retry conditions will happen during normal operations. These are completely out of RMR’s control, and there is nothing that RMR can do to avoid or mitigate these other than by allowing RMR to retry the send operation, and even then it is possible (e.g., during connection reattempts), that a single retry loop is not enough to guarantee a successful send.

RETURN VALUE

The rmr_call function returns a pointer to a message buffer with the state set to reflect the overall state of call processing (see Errors below). In some cases a nil pointer will be returned; when this is the case only errno will be available to describe the reason for failure.

ERRORS

These values are reflected in the state field of the returned message.

RMR_OK	The call was successful and the message buffer references the response message.
RMR_ERR_CALLFAILED	The call failed and the value of errno, as described below, should be checked for the specific reason.

The global “variable” errno will be set to one of the following values if the overall call processing was not successful.

ETIMEDOUT	Too many messages were queued before receiving the expected response
ENOBUFS	The queued message ring is full, messages were dropped
EINVAL	A parameter was not valid
EAGAIN	The underlying message system was interrupted or the device was busy; the message was not sent, and the user application should call this function with the message again.

EXAMPLE

The following code snippet shows one way of using the rmr_call function, and illustrates how the transaction ID must be set.

int retries_left = 5;               // max retries on dev not available
int retry_delay = 50000;            // retry delay (usec)
static rmr_mbuf_t*  mbuf = NULL;    // response msg
msg_t*  pm;                         // application struct for payload

// get a send buffer and reference the payload
mbuf = rmr_alloc_msg( mr, sizeof( pm->req ) );
pm = (msg_t*) mbuf->payload;

// generate an xaction ID and fill in payload with data and msg type
snprintf( mbuf->xaction, RMR_MAX_XID, "%s", gen_xaction() );
snprintf( pm->req, sizeof( pm->req ), "{ \\"req\\": \\"num users\\"}" );
mbuf->mtype = MT_REQ;

msg = rmr_call( mr, msg );
if( ! msg ) {               // probably a timeout and no msg received
    return NULL;            // let errno trickle up
}

if( mbuf->state != RMR_OK ) {
    while( retries_left-- > 0 &&             // loop as long as eagain
           errno == EAGAIN &&
           (msg = rmr_call( mr, msg )) != NULL &&
           mbuf->state != RMR_OK ) {

        usleep( retry_delay );
    }

    if( mbuf == NULL || mbuf->state != RMR_OK ) {
        rmr_free_msg( mbuf );        // safe if nil
        return NULL;
    }
}

// do something with mbuf

SEE ALSO

rmr_alloc_msg(3), rmr_free_msg(3), rmr_init(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_set_stimeout(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3)

Man Page: rmr_close

RMR LIBRARY FUNCTIONS

NAME

rmr_close

SYNOPSIS

#include <rmr/rmr.h>

void rmr_close( void* vctx )

DESCRIPTION

The rmr_close function closes the listen socket effectively cutting the application off. The route table listener is also stopped. Calls to rmr_rcv_msg() will fail with unpredictable error codes, and calls to rmr_send_msg(), rmr_call(), and rmr_rts_msg() will have unknown results.

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_free_msg

RMR LIBRARY FUNCTIONS

NAME

rmr_free_msg

SYNOPSIS

#include <rmr/rmr.h>

void rmr_free_msg( rmr_mbuf_t* mbuf );

DESCRIPTION

The message buffer is returned to the pool, or the associated memory is released depending on the needs of the underlying messaging system. This allows the user application to release a buffer that is not going to be used. It is safe to pass a nil pointer to this function, and doing so does not result in a change to the value of errrno.

After calling, the user application should not use any of the pointers (transaction ID, or payload) which were available.

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_init(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3)

Man Page: rmr_get_const

RMR LIBRARY FUNCTIONS

NAME

rmr_get_const

SYNOPSIS

#include <rmr/rmr.h>

unsigned char* rmr_get_const();

DESCRIPTION

The rmr_get_const function is a convenience function for wrappers which do not have the ability to “compile in” RMR constants. The function will build a nil terminated string containing JSON which defines the RMR constants that C and Go applications have at compile time via the rmr.h header file.

All values are represented as strings and the JSON format is illustrated in the following (partial) example:

{
  "RMR_MAX_XID": "32",
  "RMR_OK": "0",
  "RMR_ERR_BADARG", "1",
  "RMR_ERR_NOENDPT" "2"
}

RETURN VALUE

On success, a pointer to a string containing the JSON defining constant and value pairs. On failure a nil pointer is returned.

SEE ALSO

rmr(7)

Man Page: rmr_get_meid

RMR LIBRARY FUNCTIONS

NAME

rmr_get_meid

SYNOPSIS

#include <rmr/rmr.h>

char* rmr_get_meid( rmr_mbuf_t* mbuf, unsigned char* dest )

DESCRIPTION

The rmr_get_meid function will copy the managed entity ID (meid) field from the message into the dest buffer provided by the user. The buffer referenced by dest is assumed to be at least RMR_MAX_MEID bytes in length. If dest is NULL, then a buffer is allocated (the calling application is expected to free when the buffer is no longer needed).

RETURN VALUE

On success, a pointer to the extracted string is returned. If dest was supplied, then this is just a pointer to the caller’s buffer. If dest was NULL, this is a pointer to the allocated buffer. If an error occurs, a nil pointer is returned and errno is set as described below.

ERRORS

If an error occurs, the value of the global variable errno will be set to one of the following with the indicated meaning.

EINVAL	The message, or an internal portion of the message, was corrupted or the pointer was invalid.
ENOMEM	A nil pointer was passed for dest, however it was not possible to allocate a buffer using malloc().

SEE ALSO

rmr_alloc_msg(3), rmr_bytes2xact(3), rmr_bytes2meid(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_get_xact(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_str2xact(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_get_rcvfd

RMR LIBRARY FUNCTIONS

NAME

rmr_get_rcvfd

SYNOPSIS

#include <rmr/rmr.h>

void* rmr_get_rcvfd( void* ctx )

DESCRIPTION

The rmr_get_rcvfd function returns a file descriptor which may be given to epoll_wait() by an application that wishes to use event poll in a single thread rather than block on the arrival of a message via calls to rmr_rcv_msg(). When epoll_wait() indicates that this file descriptor is ready, a call to rmr_rcv_msg() will not block as at least one message has been received.

The context (ctx) pointer passed in is the pointer returned by the call to rmr_init().

RETURN VALUE

The rmr_get_rcvfd function returns a file descriptor greater or equal to 0 on success and -1 on error.

ERRORS

The following error values are specifically set by this RMR function. In some cases the error message of a system call is propagated up, and thus this list might be incomplete.

EINVAL

The use of this function is invalid in this environment.

EXAMPLE

The following short code bit illustrates the use of this function. Error checking has been omitted for clarity.

#include <stdio.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <rmr/rmr.h>

int main() {
    int rcv_fd;     // pollable fd
    void* mrc;      //msg router context
    struct epoll_event events[10];          // support 10 events to poll
    struct epoll_event epe;                 // event definition for event to listen to
    int     ep_fd = -1;
    rmr_mbuf_t* msg = NULL;
    int nready;
    int i;
    int norm_msg_size = 1500;               // 95% messages are less than this

    mrc = rmr_init( "43086", norm_msg_size, RMRFL_NONE );
    rcv_fd = rmr_get_rcvfd( mrc );

    ep_fd = epoll_create1( 0 );             // initialise epoll environment
    epe.events = EPOLLIN;
    epe.data.fd = rcv_fd;
    epoll_ctl( ep_fd, EPOLL_CTL_ADD, rcv_fd, &epe );    // add our info to the mix

    while( 1 ) {
        nready = epoll_wait( ep_fd, events, 10, -1 );   // -1 == block forever (no timeout)
        for( i = 0; i < nready && i < 10; i++ ) {       // loop through to find what is ready
            if( events[i].data.fd == rcv_fd ) {         // RMR has something
                msg = rmr_rcv_msg( mrc, msg );
                if( msg ) {
                    // do something with msg
                }
            }

            // check for other ready fds....
        }
    }
}

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3)

Man Page: rmr_get_src

RMR LIBRARY FUNCTIONS

NAME

rmr_get_src

SYNOPSIS

#include <rmr/rmr.h>

unsigned char* rmr_get_src( rmr_mbuf_t* mbuf, unsigned char* dest )

DESCRIPTION

The rmr_get_src function will copy the source information from the message to a buffer (dest) supplied by the user. In an RMR message, the source is the sender’s information that is used for return to sender function calls, and is generally the hostname and port in the form name. The source might be an IP address port combination; the data is populated by the sending process and the only requirement is that it be capable of being used to start a TCP session with the sender.

The maximum size allowed by RMR is 64 bytes (including the nil string terminator), so the user must ensure that the destination buffer given is at least 64 bytes.

RETURN VALUE

On success, a pointer to the destination buffer is given as a convenience to the user programme. On failure, a nil pointer is returned and the value of errno is set.

ERRORS

If an error occurs, the value of the global variable errno will be set to one of the following with the indicated meaning.

EINVAL

The message, or an internal portion of the message, was corrupted or the pointer was invalid.

SEE ALSO

rmr_alloc_msg(3), rmr_bytes2xact(3), rmr_bytes2meid(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_get_srcip(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_str2xact(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_get_srcip

RMR LIBRARY FUNCTIONS

NAME

rmr_get_srcip

SYNOPSIS

#include <rmr/rmr.h>

unsigned char* rmr_get_srcip( rmr_mbuf_t* mbuf, unsigned char* dest )

DESCRIPTION

The rmr_get_srcip function will copy the source IP address from the message to a buffer (dest) supplied by the user. In an RMR message, the source IP address is the sender’s information that is used for return to sender function calls; this function makes it available to the user application. The address is maintained as IP:port where IP could be either an IPv6 or IPv4 address depending on what was provided by the sending application.

The maximum size allowed by RMR is 64 bytes (including the nil string terminator), so the user must ensure that the destination buffer given is at least 64 bytes. The user application should use the RMR constant RMR_MAX_SRC to ensure that the buffer supplied is large enough, and to protect against future RMR enhancements which might increase the address buffer size requirement.

RETURN VALUE

On success, a pointer to the destination buffer is given as a convenience to the user programme. On failure, a nil pointer is returned and the value of errno is set.

ERRORS

If an error occurs, the value of the global variable errno will be set to one of the following with the indicated meaning.

EINVAL

The message, or an internal portion of the message, was corrupted or the pointer was invalid.

SEE ALSO

rmr_alloc_msg(3), rmr_bytes2xact(3), rmr_bytes2meid(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_get_src(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_str2xact(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_get_trace

RMR LIBRARY FUNCTIONS

NAME

rmr_get_trace

SYNOPSIS

#include <rmr/rmr.h>

int rmr_get_trace( rmr_mbuf_t* mbuf, unsigned char* dest, int size )

DESCRIPTION

The rmr_get_trace function will copy the trace information from the message into the user’s allocated memory referenced by dest. The size parameter is assumed to be the maximum number of bytes which can be copied (size of the destination buffer).

RETURN VALUE

On success, the number of bytes actually copied is returned. If the return value is 0, no bytes copied, then the reason could be that the message pointer was nil, or the size parameter was <= 0.

SEE ALSO

rmr_alloc_msg(3), rmr_tralloc_msg(3), rmr_bytes2xact(3), rmr_bytes2meid(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_get_trlen(3), rmr_init(3), rmr_init_trace(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_str2xact(3), rmr_wh_open(3), rmr_wh_send_msg(3), rmr_set_trace(3), rmr_trace_ref(3)

Man Page: rmr_get_trlen

RMR LIBRARY FUNCTIONS

NAME

rmr_get_trlen

SYNOPSIS

#include <rmr/rmr.h>

int rmr_get_trlen( rmr_mbuf_t* msg );

DESCRIPTION

Given a message buffer, this function returns the amount of space (bytes) that have been allocated for trace data. If no trace data has been allocated, then 0 is returned.

RETURN VALUE

The number of bytes allocated for trace information in the given message.

ERRORS

INVAL

Parameter(s) passed to the function were not valid.

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_trace(3), rmr_init(3), rmr_init_trace(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_set_trace(3), rmr_tralloc_msg(3)

Man Page: rmr_get_xact

RMR LIBRARY FUNCTIONS

NAME

rmr_get_xact

SYNOPSIS

#include <rmr/rmr.h>

char* rmr_get_xact( rmr_mbuf_t* mbuf, unsigned char* dest )

DESCRIPTION

The rmr_get_xact function will copy the transaction field from the message into the dest buffer provided by the user. The buffer referenced by dest is assumed to be at least RMR_MAX_XID bytes in length. If dest is NULL, then a buffer is allocated (the calling application is expected to free when the buffer is no longer needed).

RETURN VALUE

On success, a pointer to the extracted string is returned. If dest was supplied, then this is just a pointer to the caller’s buffer. If dest was NULL, this is a pointer to the allocated buffer. If an error occurs, a nil pointer is returned and errno is set as described below.

ERRORS

If an error occurs, the value of the global variable errno will be set to one of the following with the indicated meaning.

EINVAL	The message, or an internal portion of the message, was corrupted or the pointer was invalid.
ENOMEM	A nil pointer was passed for dest, however it was not possible to allocate a buffer using malloc().

SEE ALSO

rmr_alloc_msg(3), rmr_bytes2xact(3), rmr_bytes2meid(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_get_meid(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_str2xact(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_init

RMR LIBRARY FUNCTIONS

NAME

rmr_init

SYNOPSIS

#include <rmr/rmr.h>

void* rmr_init( char* proto_port, int norm_msg_size, int flags );

DESCRIPTION

The rmr_init function prepares the environment for sending and receiving messages. It does so by establishing a worker thread (pthread) which subscribes to a route table generator which provides the necessary routing information for the RMR library to send messages.

Port is used to listen for connection requests from other RMR based applications. The norm_msg_size parameter is used to allocate receive buffers and should be set to what the user application expects to be a size which will hold the vast majority of expected messages. When computing the size, the application should consider the usual payload size and the maximum trace data size that will be used. This value is also used as the default message size when allocating message buffers (when a zero size is given to rmr_alloc_msg(); see the rmr_alloc_msg() manual page). Messages arriving which are longer than the given normal size will cause RMR to allocate a new buffer which is large enough for the arriving message.

Starting with version 3.8.0 RMR no longer places a maximum buffer size for received messages. The underlying system memory manager might impose such a limit and the attempt to allocate a buffer larger than that limit will likely result in an application abort. Other than the potential performance impact from extra memory allocation and release, there is no penality to the user programme for specifyning a normal buffer size which is usually smaller than received buffers. Similarly, the only penality to the application for over specifying the normal buffer size might be a larger memory footprint.

Flags allows for selection of some RMR options at the time of initialisation. These are set by ORing RMRFL constants from the RMR header file. Currently the following flags are supported:

RMRFL_NONE	No flags are set.
RMRFL_NOTHREAD	The route table collector thread is not to be started. This should only be used by the route table generator application if it is based on RMR.
RMRFL_MTCALL	Enable multi-threaded call support.
RMRFL_NOLOCK	Some underlying transport providers (e.g. SI95) enable locking to be turned off if the user application is single threaded, or otherwise can guarantee that RMR functions will not be invoked concurrently from different threads. Turning off locking can help make message receipt more efficient. If this flag is set when the underlying transport does not support disabling locks, it will be ignored.

Multi-threaded Calling

The support for an application to issue a blocking call by the rmr_call() function was limited such that only user applications which were operating in a single thread could safely use the function. Further, timeouts were message count based and not time unit based. Multi-threaded call support adds the ability for a user application with multiple threads to invoke a blocking call function with the guarantee that the correct response message is delivered to the thread. The additional support is implemented with the rmr_mt_call() and rmr_mt_rcv() function calls.

Multi-threaded call support requires the user application to specifically enable it when RMR is initialised. This is necessary because a second, dedicated, receiver thread must be started, and requires all messages to be examined and queued by this thread. The additional overhead is minimal, queuing information is all in the RMR message header, but as an additional process is necessary the user application must “opt in” to this approach.

ENVIRONMENT

As a part of the initialisation process rmr_init reads environment variables to configure itself. The following variables are used if found.

RMR_ASYNC_CONN	Allows the async connection mode to be turned off (by setting the value to 0). When set to 1, or missing from the environment, RMR will invoke the connection interface in the transport mechanism using the non-blocking (async) mode. This will likely result in many “soft failures” (retry) until the connection is established, but allows the application to continue unimpeded should the connection be slow to set up.
RMR_BIND_IF	This provides the interface that RMR will bind listen ports to, allowing for a single interface to be used rather than listening across all interfaces. This should be the IP address assigned to the interface that RMR should listen on, and if not defined RMR will listen on all interfaces.
RMR_CTL_PORT	This variable defines the port that RMR should open for communications with Route Manager, and other RMR control applications. If not defined, the port 4561 is assumed. Previously, the RMR_RTG_SVC (route table generator service port) was used to define this port. However, a future version of Route Manager will require RMR to connect and request tables, thus that variable is now used to supply the Route Manager’s well-known address and port. To maintain backwards compatibility with the older Route Manager versions, the presence of this variable in the environment will shift RMR’s behaviour with respect to the default value used when RMR_RTG_SVC is not defined. When RMR_CTL_PORT is defined: RMR assumes that Route Manager requires RMR to connect and request table updates is made, and the default well-known address for Route manager is used (routemgr:4561). When RMR_CTL_PORT is undefined: RMR assumes that Route Manager will connect and push table updates, thus the default listen port (4561) is used. To avoid any possible misinterpretation and/or incorrect assumptions on the part of RMR, it is recommended that both the RMR_CTL_PORT and RMR_RTG_SVC be defined. In the case where both variables are defined, RMR will behave exactly as is communicated with the variable’s values.
RMR_RTREQ_FREQ	When RMR needs a new route table it will send a request once every n seconds. The default value for n is 5, but can be changed if this variable is set prior to invoking the process. Accepted values are between 1 and 300 inclusive.
RMR_RTG_SVC	The value of this variable depends on the Route Manager in use. When the Route Manager is expecting to connect to an xAPP and push route tables, this variable must indicate the port which RMR should use to listen for these connections. When the Route Manager is expecting RMR to connect and request a table update during initialisation, the variable should be the host of the Route Manager process. The RMR_CTL_PORT variable (added with the support of sending table update requests to Route manager), controls the behaviour if this variable is not set. See the description of that variable for details.
RMR_HR_LOG	By default RMR writes messages to standard error (incorrectly referred to as log messages) in human readable format. If this environment variable is set to 0, the format of standard error messages might be written in some format not easily read by humans. If missing, a value of 1 is assumed.
RMR_LOG_VLEVEL	This is a numeric value which corresponds to the verbosity level used to limit messages written to standard error. The lower the number the less chatty RMR functions are during execution. The following is the current relationship between the value set on this variable and the messages written: 0 Off; no messages of any sort are written. 1 Only critical messages are written (default if this variable does not exist) 2 Errors and all messages written with a lower value. 3 Warnings and all messages written with a lower value. 4 Informational and all messages written with a lower value. 5 Debugging mode – all messages written, however this requires RMR to have been compiled with debugging support enabled.
RMR_RTG_ISRAW	Deprecated. Should be set to 1 if the route table generator is sending “plain” messages (not using RMR to send messages), 0 if the RTG is using RMR to send. The default is 1 as we don’t expect the RTG to use RMR. This variable is only recognised when using the NNG transport library as it is not possible to support NNG “raw” communications with other transport libraries. It is also necessary to match the value of this variable with the capabilities of the Route Manager; at some point in the future RMR will assume that all Route Manager messages will arrive via an RMR connection and will ignore this variable.
RMR_SEED_RT	This is used to supply a static route table which can be used for debugging, testing, or if no route table generator process is being used to supply the route table. If not defined, no static table is used and RMR will not report ready until a table is received. The static route table may contain both the route table (between newrt start and end records), and the MEID map (between meid_map start and end records).
RMR_SRC_ID	This is either the name or IP address which is placed into outbound messages as the message source. This will used when an RMR based application uses the rmr_rts_msg() function to return a response to the sender. If not supplied RMR will use the hostname which in some container environments might not be routable. The value of this variable is also used for Route Manager messages which are sent via an RMR connection.
RMR_VCTL_FILE	This supplies the name of a verbosity control file. The core RMR functions do not produce messages unless there is a critical failure. However, the route table collection thread, not a part of the main message processing component, can write additional messages to standard error. If this variable is set, RMR will extract the verbosity level for these messages (0 is silent) from the first line of the file. Changes to the file are detected and thus the level can be changed dynamically, however RMR will only suss out this variable during initialisation, so it is impossible to enable verbosity after startup.
RMR_WARNINGS	If set to 1, RMR will write some warnings which are non-performance impacting. If the variable is not defined, or set to 0, RMR will not write these additional warnings.

RETURN VALUE

The rmr_init function returns a void pointer (a context if you will) that is passed as the first parameter to nearly all other RMR functions. If rmr_init is unable to properly initialise the environment, NULL is returned and errno is set to an appropriate value.

ERRORS

The following error values are specifically set by this RMR function. In some cases the error message of a system call is propagated up, and thus this list might be incomplete.

ENOMEM

Unable to allocate memory.

EXAMPLE

void*  uh;
rmr_mbuf* buf = NULL;

uh = rmr_init( "43086", 4096, 0 );
buf = rmr_rcv_msg( uh, buf );

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_mt_call(3), rmr_mt_rcv(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3)

Man Page: rmr_init_trace

RMR LIBRARY FUNCTIONS

NAME

rmr_init_trace

SYNOPSIS

#include <rmr/rmr.h>

void* rmr_init_trace( void* ctx )

DESCRIPTION

The rmr_init_trace function establishes the default trace space placed in each message buffer allocated with rmr_alloc_msg(). If this function is never called, then no trace space is allocated by default into any message buffer.

Trace space allows the user application to pass some trace token, or other data with the message, but outside of the payload. Trace data may be added to any message with rmr_set_trace(), and may be extracted from a message with rmr_get_trace(). The number of bytes that a message contains for/with trace data can be determined by invoking rmr_get_trlen().

This function may be safely called at any time during the life of the user programme to (re)set the default trace space reserved. If the user programme needs to allocate a message with trace space of a different size than is allocated by default, without fear of extra overhead of reallocating a message later, the rmr_tralloc_msg() function can be used.

RETURN VALUE

A value of 1 is returned on success, and 0 on failure. A failure indicates that the RMR context (a void pointer passed to this function was not valid.

SEE ALSO

rmr_alloc_msg(3), rmr_tr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_get_trace(3), rmr_get_trlen(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_set_trace(3)

Man Page: rmr_mt_call

RMR LIBRARY FUNCTIONS

NAME

rmr_mt_call

SYNOPSIS

#include <rmr/rmr.h>

extern rmr_mbuf_t* rmr_mt_call( void* vctx, rmr_mbuf_t* msg, int id, int timeout );

DESCRIPTION

The rmr_mt_call function sends the user application message to a remote endpoint, and waits for a corresponding response message before returning control to the user application. The user application supplies a completed message buffer, as it would for a rmr_send_msg call, but unlike with a send, the buffer returned will have the response from the application that received the message. The thread invoking the rmr_mt_call() will block until a message arrives or until timeout milliseconds has passed; which ever comes first. Using a timeout value of zero (0) will cause the thread to block without a timeout.

The id supplied as the third parameter is an integer in the range of 2 through 255 inclusive. This is a caller defined “thread number” and is used to match the response message with the correct user application thread. If the ID value is not in the proper range, the attempt to make the call will fail.

Messages which are received while waiting for the response are queued on a normal receive queue and will be delivered to the user application with the next invocation of rmr_mt_rcv() or rmr_rvv_msg(). by RMR, and are returned to the user application when rmr_rcv_msg is invoked. These messages are returned in the order received, one per call to rmr_rcv_msg.

The Transaction ID

The user application is responsible for setting the value of the transaction ID field before invoking rmr_mt_call. The transaction ID is a RMR_MAX_XID byte field that is used to match the response message when it arrives. RMR will compare all of the bytes in the field, so the caller must ensure that they are set correctly to avoid missing the response message. The application which returns the response message is also expected to ensure that the return buffer has the matching transaction ID. This can be done transparently if the application uses the rmr_rts_msg() function and does not adjust the transaction ID.

Retries

The send operations in RMR will retry soft send failures until one of three conditions occurs:

• The message is sent without error

• The underlying transport reports a hard failure

• The maximum number of retry loops has been attempted

A retry loop consists of approximately 1000 send attempts without any intervening calls to sleep() or usleep(). The number of retry loops defaults to 1, thus a maximum of 1000 send attempts is performed before returning to the user application. This value can be set at any point after RMR initialisation using the rmr_set_stimeout() function allowing the user application to completely disable retires (set to 0), or to increase the number of retry loops.

Transport Level Blocking

The underlying transport mechanism used to send messages is configured in non-blocking mode. This means that if a message cannot be sent immediately the transport mechanism will not pause with the assumption that the inability to send will clear quickly (within a few milliseconds). This means that when the retry loop is completely disabled (set to 0), that the failure to accept a message for sending by the underlying mechanisms (software or hardware) will be reported immediately to the user application.

It should be noted that depending on the underlying transport mechanism being used, it is extremely likely that retry conditions will happen during normal operations. These are completely out of RMR’s control, and there is nothing that RMR can do to avoid or mitigate these other than by allowing RMR to retry the send operation, and even then it is possible (e.g., during connection reattempts), that a single retry loop is not enough to guarantee a successful send.

RETURN VALUE

The rmr_mt_call function returns a pointer to a message buffer with the state set to reflect the overall state of call processing. If the state is RMR_OK then the buffer contains the response message; otherwise the state indicates the error encountered while attempting to send the message.

If no response message is received when the timeout period has expired, a nil pointer will be returned (NULL).

ERRORS

These values are reflected in the state field of the returned message.

RMR_OK	The call was successful and the message buffer references the response message.
RMR_ERR_BADARG	An argument passed to the function was invalid.
RMR_ERR_CALLFAILED	The call failed and the value of errno, as described below, should be checked for the specific reason.
RMR_ERR_NOENDPT	An endpoint associated with the message type could not be found in the route table.
RMR_ERR_RETRY	The underlying transport mechanism was unable to accept the message for sending. The user application can retry the call operation if appropriate to do so.

The global “variable” errno will be set to one of the following values if the overall call processing was not successful.

ETIMEDOUT	Too many messages were queued before receiving the expected response
ENOBUFS	The queued message ring is full, messages were dropped
EINVAL	A parameter was not valid
EAGAIN	The underlying message system wsa interrupted or the device was busy; the message was not sent, and user application should call this function with the message again.

EXAMPLE

The following code bit shows one way of using the rmr_mt_call function, and illustrates how the transaction ID must be set.

int retries_left = 5;               // max retries on dev not available
static rmr_mbuf_t*  mbuf = NULL;    // response msg
msg_t*  pm;                         // appl message struct (payload)

// get a send buffer and reference the payload
mbuf = rmr_alloc_msg( mr, sizeof( pm->req ) );
pm = (msg_t*) mbuf->payload;

// generate an xaction ID and fill in payload with data and msg type
rmr_bytes2xact( mbuf, xid, RMR_MAX_XID );
snprintf( pm->req, sizeof( pm->req ), "{ \\"req\\": \\"num users\\"}" );
mbuf->mtype = MT_USR_RESP;

msg = rmr_mt_call( mr, msg, my_id, 100 );        // wait up to 100ms
if( ! msg ) {               // probably a timeout and no msg received
    return NULL;            // let errno trickle up
}

if( mbuf->state != RMR_OK ) {
    while( retries_left-- > 0 &&             // loop as long as eagain
           mbuf->state == RMR_ERR_RETRY &&
           (msg = rmr_mt_call( mr, msg )) != NULL &&
           mbuf->state != RMR_OK ) {

        usleep( retry_delay );
    }

    if( mbuf == NULL || mbuf->state != RMR_OK ) {
        rmr_free_msg( mbuf );        // safe if nil
        return NULL;
    }
}

// do something with mbuf

SEE ALSO

rmr_alloc_msg(3), rmr_free_msg(3), rmr_init(3), rmr_mt_rcv(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_set_stimeout(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3)

Man Page: rmr_mt_rcv

RMR LIBRARY FUNCTIONS

NAME

rmr_mt_rcv

SYNOPSIS

#include <rmr/rmr.h>

rmr_mbuf_t* rmr_mt_rcv( void* vctx, rmr_mbuf_t* old_msg, int timeout );

DESCRIPTION

The rmr_mt_rcv function blocks until a message is received, or the timeout period (milliseconds) has passed. The result is an RMR message buffer which references a received message. In the case of a timeout the state will be reflected in an “empty buffer” (if old_msg was not nil, or simply with the return of a nil pointer. If a timeout value of zero (0) is given, then the function will block until the next message received.

The vctx pointer is the pointer returned by the rmr_init function. Old_msg is a pointer to a previously used message buffer or NULL. The ability to reuse message buffers helps to avoid alloc/free cycles in the user application. When no buffer is available to supply, the receive function will allocate one.

The old_msg parameter allows the user to pass a previously generated RMR message back to RMR for reuse. Optionally, the user application may pass a nil pointer if no reusable message is available. When a timeout occurs, and old_msg was not nil, the state will be returned by returning a pointer to the old message with the state set.

It is possible to use the rmr_rcv_msg() function instead of this function. Doing so might be advantageous if the user programme does not always start the multi-threaded mode and the use of rmr_rcv_msg() would make the flow of the code more simple. The advantages of using this function are the ability to set a timeout without using epoll, and a small performance gain (if multi-threaded mode is enabled, and the rmr_rcv_msg() function is used, it simply invokes this function without a timeout value, thus there is the small cost of a second call that results). Similarly, the rmr_torcv_msg() call can be used when in multi-threaded mode with the same “pass through” overhead to using this function directly.

RETURN VALUE

When a message is received before the timeout period expires, a pointer to the RMR message buffer which describes the message is returned. This will, with a high probability, be a different message buffer than old_msg; the user application should not continue to use old_msg after it is passed to this function.

In the event of a timeout the return value will be the old msg with the state set, or a nil pointer if no old message was provided.

ERRORS

The state field in the message buffer will be set to one of the following values:

RMR_OK	The message was received without error.
RMR_ERR_BADARG	A parameter passed to the function was not valid (e.g. a nil pointer). indicate either RMR_OK or RMR_ERR_EMPTY if an empty message was received.
RMR_ERR_EMPTY	The message received had no associated data. The length of the message will be 0.
RMR_ERR_NOTSUPP	The multi-threaded option was not enabled when RMR was initialised. See the man page for rmr_init() for details.
RMR_ERR_RCVFAILED	A hard error occurred preventing the receive from completing.

When a nil pointer is returned, or any other state value was set in the message buffer, errno will be set to one of the following:

INVAL	Parameter(s) passed to the function were not valid.
EBADF	The underlying message transport is unable to process the request.
ENOTSUP	The underlying message transport is unable to process the request.
EFSM	The underlying message transport is unable to process the request.
EAGAIN	The underlying message transport is unable to process the request.
EINTR	The underlying message transport is unable to process the request.
ETIMEDOUT	The underlying message transport is unable to process the request.
ETERM	The underlying message transport is unable to process the request.

EXAMPLE

rmr_mbuf_t*  mbuf = NULL;   // received msg

msg = rmr_mt_recv( mr, mbuf, 100 );     // wait up to 100ms
if( msg != NULL ) {
    switch( msg->state ) {
        case RMR_OK:
            printf( "got a good message\\n" );
            break;

        case RMR_ERR_EMPTY:
            printf( "received timed out\\n" );
            break;

        default:
            printf( "receive error: %d\\n", mbuf->state );
            break;
    }
} else {
    printf( "receive timeout (nil)\\n" );
}

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_init(3), rmr_mk_ring(3), rmr_mt_call(3), rmr_payload_size(3), rmr_send_msg(3), rmr_torcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_ring_free(3), rmr_torcv_msg(3)

Man Page: rmr_payload_size

RMR LIBRARY FUNCTIONS

NAME

rmr_payload_size

SYNOPSIS

#include <rmr/rmr.h>

int rmr_payload_size( rmr_mbuf_t* msg );

DESCRIPTION

Given a message buffer, this function returns the amount of space (bytes) available for the user application to consume in the message payload. This is different than the message length available as a field in the message buffer.

RETURN VALUE

The number of bytes available in the payload.

ERRORS

INVAL

Parameter(s) passed to the function were not valid.

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3)

Man Page: rmr_rcv_msg

RMR LIBRARY FUNCTIONS

NAME

rmr_rcv_msg

SYNOPSIS

#include <rmr/rmr.h>

rmr_mbuf_t* rmr_rcv_msg( void* vctx, rmr_mbuf_t* old_msg );

DESCRIPTION

The rmr_rcv_msg function blocks until a message is received, returning the message to the caller via a pointer to a rmr_mbuf_t structure type. If messages were queued while waiting for the response to a previous invocation of rmr_call, the oldest message is removed from the queue and returned without delay.

The vctx pointer is the pointer returned by the rmr_init function. Old_msg is a pointer to a previously used message buffer or NULL. The ability to reuse message buffers helps to avoid alloc/free cycles in the user application. When no buffer is available to supply, the receive function will allocate one.

RETURN VALUE

The function returns a pointer to the rmr_mbuf_t structure which references the message information (state, length, payload), or a nil pointer in the case of an extreme error.

ERRORS

The state field in the message buffer will indicate RMR_OK when the message receive process was successful and the message can be used by the caller. Depending on the underlying transport mechanism, one of the following RMR error stats may be returned:

RMR_ERR_EMPTY	The message received had no payload, or was completely empty.
RMR_ERR_TIMEOUT	For some transport mechanisms, or if reading the receive queue from multiple threads, it is possible for one thread to find no data waiting when it queries the queue. When this state is reported, the message buffer does not contain message data and the user application should reinvoke the receive function.

When an RMR error state is reported, the underlying errno value might provide more information. The following is a list of possible values that might accompany the states listed above:

RMR_ERR_EMPTY if an empty message was received. If a nil pointer is returned, or any other state value was set in the message buffer, errno will be set to one of the following:

INVAL	Parameter(s) passed to the function were not valid.
EBADF	The underlying message transport is unable to process the request.
ENOTSUP	The underlying message transport is unable to process the request.
EFSM	The underlying message transport is unable to process the request.
EAGAIN	The underlying message transport is unable to process the request.
EINTR	The underlying message transport is unable to process the request.
ETIMEDOUT	The underlying message transport is unable to process the request.
ETERM	The underlying message transport is unable to process the request.

EXAMPLE

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_init(3), rmr_mk_ring(3), rmr_payload_size(3), rmr_send_msg(3), rmr_torcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_ring_free(3), rmr_torcv_msg(3)

Man Page: rmr_ready

RMR LIBRARY FUNCTIONS

NAME

rmr_ready

SYNOPSIS

#include <rmr/rmr.h>

int rmr_ready( void* vctx );

DESCRIPTION

The rmr_ready function checks to see if a routing table has been successfully received and installed. The return value indicates the state of readiness.

RETURN VALUE

A return value of 1 (true) indicates that the routing table is in place and attempts to send messages can be made. When 0 is returned (false) the routing table has not been received and thus attempts to send messages will fail with no endpoint errors.

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3)

Man Page: rmr_realloc_payload

RMR LIBRARY FUNCTIONS

NAME

rmr_realloc_payload

SYNOPSIS

#include <rmr/rmr.h>

extern rmr_mbuf_t* rmr_realloc_payload( rmr_mbuf_t* msg, int new_len, int copy, int clone );

DESCRIPTION

The rmr_realloc_payload function will return a pointer to an RMR message buffer struct (rmr_mbuf_t) which has a payload large enough to accomodate new_len bytes. If necessary, the underlying payload is reallocated, and the bytes from the original payload are copied if the copy parameter is true (1). If the message passed in has a payload large enough, there is no additional memory allocation and copying.

Cloning The Message Buffer

This function can also be used to generate a separate copy of the original message, with the desired payload size, without destroying the original message buffer or the original payload. A standalone copy is made only when the clone parameter is true (1). When cloning, the payload is copied to the cloned message only if the copy parameter is true.

Message Buffer Metadata

The metadata in the original message buffer (message type, subscription ID, and payload length) will be preserved if the copy parameter is true. When this parameter is not true (0), then these values are set to the uninitialised value (-1) for type and ID, and the length is set to 0.

RETURN VALUE

The rmr_realloc_payload function returns a pointer to the message buffer with the payload which is large enough to hold new_len bytes. If the clone option is true, this will be a pointer to the newly cloned message buffer; the original message buffer pointer may still be used to reference that message. It is the calling application’s responsibility to free the memory associateed with both messages using the rmr_free_msg() function.

When the clone option is not used, it is still good practice by the calling application to capture and use this reference as it is possible that the message buffer, and not just the payload buffer, was reallocated. In the event of an error, a nil pointer will be returned and the value of errno will be set to reflect the problem.

ERRORS

These value of errno will reflect the error condition if a nil pointer is returned:

ENOMEM	Memory allocation of the new payload failed.
EINVAL	The pointer passed in was nil, or referenced an invalid message, or the required length was not valid.

EXAMPLE

The following code bit illustrates how this function can be used to reallocate a buffer for a return to sender acknowledgement message which is larger than the message received.

  if( rmr_payload_size( msg ) < ack_sz ) {              // received message too small for ack
    msg = rmr_realloc_payload( msg, ack_sz, 0, 0 );     // reallocate the message with a payload big enough
    if( msg == NULL ) {
      fprintf( stderr, "[ERR] realloc returned a nil pointer: %s\\n", strerror( errno ) );
    } else {
      // populate and send ack message
    }
}

SEE ALSO

rmr_alloc_msg(3), rmr_free_msg(3), rmr_init(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_set_stimeout(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3)

Man Page: rmr_rts_msg

RMR LIBRARY FUNCTIONS

NAME

rmr_rts_msg

SYNOPSIS

#include <rmr/rmr.h>

rmr_mbuf_t*  rmr_rts_msg( void* vctx, rmr_mbuf_t* msg );

DESCRIPTION

The rmr_rts_msg function sends a message returning it to the endpoint which sent the message rather than selecting an endpoint based on the message type and routing table. Other than this small difference, the behaviour is exactly the same as rmr_send_msg.

Retries

The send operations in RMR will retry soft send failures until one of three conditions occurs:

• The message is sent without error

• The underlying transport reports a hard failure

• The maximum number of retry loops has been attempted

A retry loop consists of approximately 1000 send attempts without any intervening calls to sleep() or usleep(). The number of retry loops defaults to 1, thus a maximum of 1000 send attempts is performed before returning to the user application. This value can be set at any point after RMR initialisation using the rmr_set_stimeout() function allowing the user application to completely disable retires (set to 0), or to increase the number of retry loops.

Transport Level Blocking

The underlying transport mechanism used to send messages is configured in non-blocking mode. This means that if a message cannot be sent immediately the transport mechanism will not pause with the assumption that the inability to send will clear quickly (within a few milliseconds). This means that when the retry loop is completely disabled (set to 0), that the failure to accept a message for sending by the underlying mechanisms (software or hardware) will be reported immediately to the user application.

It should be noted that depending on the underlying transport mechanism being used, it is extremely likely that retry conditions will happen during normal operations. These are completely out of RMR’s control, and there is nothing that RMR can do to avoid or mitigate these other than by allowing RMR to retry the send operation, and even then it is possible (e.g., during connection reattempts), that a single retry loop is not enough to guarantee a successful send.

PAYLOAD SIZE

When crafting a response based on a received message, the user application must take care not to write more bytes to the message payload than the allocated message has. In the case of a received message, it is possible that the response needs to be larger than the payload associated with the inbound message. In order to use the return to sender function, the source information in the original message must be present in the response; information which cannot be added to a message buffer allocated through the standard RMR allocation function. To allocate a buffer with a larger payload, and which retains the necessary sender data needed by this function, the rmr_realloc_payload() function must be used to extend the payload to a size suitable for the response.

RETURN VALUE

On success, a new message buffer, with an empty payload, is returned for the application to use for the next send. The state in this buffer will reflect the overall send operation state and should be RMR_OK.

If the state in the returned buffer is anything other than RMR_OK, the user application may need to attempt a retransmission of the message, or take other action depending on the setting of errno as described below.

In the event of extreme failure, a nil pointer is returned. In this case the value of errno might be of some use, for documentation, but there will be little that the user application can do other than to move on.

ERRORS

The following values may be passed back in the state field of the returned message buffer.

RMR_ERR_BADARG	The message buffer pointer did not refer to a valid message.
RMR_ERR_NOHDR	The header in the message buffer was not valid or corrupted.
RMR_ERR_NOENDPT	The message type in the message buffer did not map to a known endpoint.
RMR_ERR_SENDFAILED	The send failed; errno has the possible reason.

The following values may be assigned to errno on failure.

INVAL	Parameter(s) passed to the function were not valid, or the underlying message processing environment was unable to interpret the message.
ENOKEY	The header information in the message buffer was invalid.
ENXIO	No known endpoint for the message could be found.
EMSGSIZE	The underlying transport refused to accept the message because of a size value issue (message was not attempted to be sent).
EFAULT	The message referenced by the message buffer is corrupt (nil pointer or bad internal length).
EBADF	Internal RMR error; information provided to the message transport environment was not valid.
ENOTSUP	Sending was not supported by the underlying message transport.
EFSM	The device is not in a state that can accept the message.
EAGAIN	The device is not able to accept a message for sending. The user application should attempt to resend.
EINTR	The operation was interrupted by delivery of a signal before the message was sent.
ETIMEDOUT	The underlying message environment timed out during the send process.
ETERM	The underlying message environment is in a shutdown state.

EXAMPLE

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_set_stimeout(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3)

Man Page: rmr_send_msg

RMR LIBRARY FUNCTIONS

NAME

rmr_send_msg

SYNOPSIS

#include <rmr/rmr.h>

rmr_mbuf_t* rmr_send_msg( void* vctx, rmr_mbuf_t* msg );

DESCRIPTION

The rmr_send_msg function accepts a message buffer from the user application and attempts to send it. The destination of the message is selected based on the message type specified in the message buffer, and the matching information in the routing tables which are currently in use by the RMR library. This may actually result in the sending of the message to multiple destinations which could degrade expected overall performance of the user application. (Limiting excessive sending of messages is the responsibility of the application(s) responsible for building the routing table used by the RMR library, and not the responsibility of the library.)

Retries

The send operations in RMR will retry soft send failures until one of three conditions occurs:

• The message is sent without error

• The underlying transport reports a hard failure

• The maximum number of retry loops has been attempted

A retry loop consists of approximately 1000 send attempts without any intervening calls to sleep() or usleep(). The number of retry loops defaults to 1, thus a maximum of 1000 send attempts is performed before returning to the user application. This value can be set at any point after RMR initialisation using the rmr_set_stimeout() function allowing the user application to completely disable retires (set to 0), or to increase the number of retry loops.

Transport Level Blocking

The underlying transport mechanism used to send messages is configured in non-blocking mode. This means that if a message cannot be sent immediately the transport mechanism will not pause with the assumption that the inability to send will clear quickly (within a few milliseconds). This means that when the retry loop is completely disabled (set to 0), that the failure to accept a message for sending by the underlying mechanisms (software or hardware) will be reported immediately to the user application.

It should be noted that depending on the underlying transport mechanism being used, it is extremely likely that retry conditions will happen during normal operations. These are completely out of RMR’s control, and there is nothing that RMR can do to avoid or mitigate these other than by allowing RMR to retry the send operation, and even then it is possible (e.g., during connection reattempts), that a single retry loop is not enough to guarantee a successful send.

RETURN VALUE

On success, a new message buffer, with an empty payload, is returned for the application to use for the next send. The state in this buffer will reflect the overall send operation state and will be RMR_OK when the send was successful.

When the message cannot be successfully sent this function will return the unsent (original) message buffer with the state set to indicate the reason for failure. The value of errno may also be set to reflect a more detailed failure reason if it is known.

In the event of extreme failure, a nil pointer is returned. In this case the value of errno might be of some use, for documentation, but there will be little that the user application can do other than to move on.

CAUTION: In some cases it is extremely likely that the message returned by the send function does not reference the same memory structure. Thus is important for the user programme to capture the new pointer for future use or to be passed to rmr_free(). If you are experiencing either double free errors or segment faults in either rmr_free() or rmr_send_msg(), ensure that the return value from this function is being captured and used.

ERRORS

The following values may be passed back in the state field of the returned message buffer.

RMR_RETRY	The message could not be sent, but the underlying transport mechanism indicates that the failure is temporary. If the send operation is tried again it might be successful.
RMR_SEND_FAILED	The send operation was not successful and the underlying transport mechanism indicates a permanent (hard) failure; retrying the send is not possible.
RMR_ERR_BADARG	The message buffer pointer did not refer to a valid message.
RMR_ERR_NOHDR	The header in the message buffer was not valid or corrupted.
RMR_ERR_NOENDPT	The message type in the message buffer did not map to a known endpoint.

The following values may be assigned to errno on failure.

INVAL	Parameter(s) passed to the function were not valid, or the underlying message processing environment was unable to interpret the message.
ENOKEY	The header information in the message buffer was invalid.
ENXIO	No known endpoint for the message could be found.
EMSGSIZE	The underlying transport refused to accept the message because of a size value issue (message was not attempted to be sent).
EFAULT	The message referenced by the message buffer is corrupt (nil pointer or bad internal length).
EBADF	Internal RMR error; information provided to the message transport environment was not valid.
ENOTSUP	Sending was not supported by the underlying message transport.
EFSM	The device is not in a state that can accept the message.
EAGAIN	The device is not able to accept a message for sending. The user application should attempt to resend.
EINTR	The operation was interrupted by delivery of a signal before the message was sent.
ETIMEDOUT	The underlying message environment timed out during the send process.
ETERM	The underlying message environment is in a shutdown state.

EXAMPLE

The following is a simple example of how the rmr_send_msg function is called. In this example, the send message buffer is saved between calls and reused eliminating alloc/free cycles.

static rmr_mbuf_t*  send_msg = NULL;        // message to send; reused on each call
msg_t*  send_pm;                            // payload for send
msg_t*  pm;                                 // our message format in the received payload

if( send_msg  == NULL ) {
    send_msg = rmr_alloc_msg( mr, MAX_SIZE ); // new buffer to send
}

// reference payload and fill in message type
pm = (msg_t*) send_msg->payload;
send_msg->mtype = MT_ANSWER;

msg->len = generate_data( pm );       // something that fills the payload in
msg = rmr_send_msg( mr, send_msg );   // ensure new pointer used after send
if( ! msg ) {
    return ERROR;
} else {
    if( msg->state != RMR_OK ) {
        // check for RMR_ERR_RETRY, and resend if needed
        // else return error
    }
}
return OK;

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_payload_size(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_torcv_rcv(3), rmr_wh_send_msg(3)

Man Page: rmr_set_fack

RMR LIBRARY FUNCTIONS

NAME

rmr_set_fack

SYNOPSIS

#include <rmr/rmr.h>

void rmr_set_fack( void* vctx );

DESCRIPTION

The rmr_set_fack function enables fast TCP acknowledgements if the underlying transport library supports it. This might be useful for applications which must send messages at a maximum rate.

RETURN VALUE

There is no return value.

ERRORS

This function does not generate any errors.

SEE ALSO

rmr_init(3),

Man Page: rmr_set_low_lat

RMR LIBRARY FUNCTIONS

NAME

rmr_set_low_latency

SYNOPSIS

#include <rmr/rmr.h>

void rmr_set_low_latency( void* vctx );

DESCRIPTION

The rmr_set_low_latency function enables TCP NO_DELAY if the underlying transport library supports it. This might be useful for applications which must send messages at a maximum rate.

A call to this function will cause all subsequent connections made by the application to set the no delay (low latency) option. When no delay is needed, it is recommended that this function be called immediately upon a successful call to the RMR initialisation function.

The effect of setting “low latency” mode is to disable Nagel’s algorithm and to send a packet on a connection as soon as it is given to the TCP transport. When this option is not enabled, TCP may employ Nagel’s algorithm and hold the packet with the assumption that it can be combined with another and sent in the same datagram in an effort to improve bandwidth but at the expense of added latency.

RETURN VALUE

There is no return value.

ERRORS

This function does not generate any errors.

SEE ALSO

rmr_init(3), rmr_fast_ack(3)

Man Page: rmr_set_stimeout

RMR LIBRARY FUNCTIONS

NAME

rmr_set_stimeout

SYNOPSIS

#include <rmr/rmr.h>

int rmr_set_stimeout( void* vctx, int rloops );

DESCRIPTION

The rmr_set_stimeout function sets the configuration for how RMR will retry message send operations which complete with either a timeout or again completion value. (Send operations include all of the possible message send functions: rmr_send_msg(), rmr_call(), rmr_rts_msg() and rmr_wh_send_msg(). The rloops parameter sets the maximum number of retry loops that will be attempted before giving up and returning the unsuccessful state to the user application. Each retry loop is approximately 1000 attempts, and RMR does not invoke any sleep function between retries in the loop; a small, 1 mu-sec, sleep is executed between loop sets if the rloops value is greater than 1.

Disabling Retries

By default, the send operations will execute with an rloop setting of 1; each send operation will attempt to resend the message approximately 1000 times before giving up. If the user application does not want to have send operations retry when the underlying transport mechanism indicates timeout or again, the application should invoke this function and pass a value of 0 (zero) for rloops. With this setting, all RMR send operations will attempt a send operation only once, returning immediately to the caller with the state of that single attempt.

RETURN VALUE

This function returns a -1 to indicate that the rloops value could not be set, and the value RMR_OK to indicate success.

ERRORS

Currently errno is not set by this function; the only cause of a failure is an invalid context (vctx) pointer.

EXAMPLE

The following is a simple example of how the rmr_set_stimeout function is called.

#define NO_FLAGS    0

char* port = "43086";     // port for message router listen
int   max_size = 4096;    // max message size for default allocations
void* mr_context;         // message router context

mr_context = rmr_init( port, max_size, NO_FLAGS );
if( mr_context != NULL ) {
    rmr_set_stimeout( mr_context, 0 );    // turn off retries
}

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_payload_size(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_send_msg(3), rmr_torcv_rcv(3), rmr_wh_send_msg(3)

Man Page: rmr_set_trace

RMR LIBRARY FUNCTIONS

NAME

rmr_set_trace

SYNOPSIS

#include <rmr/rmr.h>

int rmr_set_trace( rmr_mbuf_t* mbuf, unsigned char* data, int len )

DESCRIPTION

The rmr_set_trace function will copy len bytes from data into the trace portion of mbuf. If the trace area of mbuf is not the correct size, the message buffer will be reallocated to ensure that enough space is available for the trace data.

RETURN VALUE

The rmr_set_trace function returns the number of bytes successfully copied to the message. If 0 is returned either the message pointer was nil, or the size in the parameters was <= 0.

SEE ALSO

rmr_alloc_msg(3), rmr_tralloc_msg(3), rmr_bytes2xact(3), rmr_bytes2payload(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_get_meid(3), rmr_get_trace(3), rmr_get_trlen(3), rmr_init(3), rmr_init_trace(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_str2xact(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_set_vlevel

RMR LIBRARY FUNCTIONS

NAME

rmr_set_vlevel

SYNOPSIS

#include <rmr/rmr.h>
#include <rmr/rmr_logging.h>

void rmr_set_vlevel( int new_level )

DESCRIPTION

The rmr_set_vlevel allows the user programme to set the verbosity level which is used to determine the messages RMR writes to standard error. The new_vlevel value must be one of the following constants which have the indicated meanings:

RMR_VL_OFF	Turns off all message writing. This includes the stats and debugging messages generated by the route collector thread which are normally affected only by the externally managed verbose level file (and related environment variable).
RMR_VL_CRIT	Write only messages of critical importance. From the point of view of RMR, when a critical proper behaviour of the library cannot be expected or guaranteed.
RMR_VL_ERR	Include error messages in the output. An error is an event from which RMR has no means to recover. Continued proper execution is likely except where the affected connection and/or component mentioned in the error is concerned.
RMR_VL_WARN	Include warning messages in the output. A warning indicates an event which is not considered to be normal, but is expected and continued acceptable behaviour of the system is assured.
RMR_VL_INFO	Include informational messagees in the output. Informational messages include some diagnostic information which explain the activities of RMR.
RMR_VL_DEBUG	Include all debugging messages in the output. Debugging must have also been enabled during the build as a precaution to accidentally enabling this level of output as it can grossly affect performance.

Generally RMR does not write messages to the standard error device from critical path functions, therefore it is usually not harmful to enable a verbosity level of either RMR_VL_CRIT or RMR_VL_ERR.

Messages written from the route table collection thread are still governed by the value placed into the verbose level control file (see the man page for rmr_init()); those messages are affected only when logging is completely disabled by passing RMR_VL_OFF to this function.

The verbosity level can also be set via an environment variable prior to the start of the RMR based application. The environment variable is read only during initialisation; if the programme must change the value during execution, this function must be used. The default value, if this function is never called, and the environment variable is not present, is RMR_VL_ERR.

SEE ALSO

rmr_init(3)

Man Page: rmr_str2meid

RMR LIBRARY FUNCTIONS

NAME

rmr_str2meid

SYNOPSIS

#include <rmr/rmr.h>

int rmr_str2meid( rmr_mbuf_t* mbuf, unsigned char* src, int len )

DESCRIPTION

The rmr_str2meid function will copy the string pointed to by src to the managed entity ID (meid) field in the given message. The field is a fixed length, gated by the constant RMR_MAX_MEID and if string length is larger than this value, then nothing will be copied. (Note, this differs slightly from the behaviour of the lrmr_bytes2meid() function.)

RETURN VALUE

On success, the value RMR_OK is returned. If the string cannot be copied to the message, the return value will be one of the errors listed below.

ERRORS

If the return value is not RMR_OK, then it will be set to one of the values below.

RMR_ERR_BADARG	The message, or an internal portion of the message, was corrupted or the pointer was invalid.
RMR_ERR_OVERFLOW	The length passed in was larger than the maximum length of the field; only a portion of the source bytes were copied.

EXAMPLE

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_meid(3), rmr_get_rcvfd(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_bytes2meid(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_str2xact

RMR LIBRARY FUNCTIONS

NAME

rmr_str2xact

SYNOPSIS

#include <rmr/rmr.h>

int rmr_str2xact( rmr_mbuf_t* mbuf, unsigned char* src, int len )

DESCRIPTION

The rmr_str2xact function will copy the string pointed to by src to the transaction ID (xaction) field in the given message. The field is a fixed length, gated by the constant RMR_MAX_XID and if string length is larger than this value, then nothing will be copied. (Note, this differs slightly from the behaviour of the lrmr_bytes2xact() function.)

RETURN VALUE

On success, the value RMR_OK is returned. If the string cannot be copied to the message, the return value will be one of the errors listed below.

ERRORS

If the return value is not RMR_OK, then it will be set to one of the values below.

RMR_ERR_BADARG	The message, or an internal portion of the message, was corrupted or the pointer was invalid.
RMR_ERR_OVERFLOW	The length passed in was larger than the maximum length of the field; only a portion of the source bytes were copied.

EXAMPLE

SEE ALSO

rmr_alloc_msg(3), rmr_bytes2meid(3), rmr_bytes2xact(3), rmr_call(3), rmr_free_msg(3), rmr_get_meid(3), rmr_get_rcvfd(3), rmr_get_xact(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_support

RMR LIBRARY FUNCTIONS

NAME

RMR support functions

SYNOPSIS

#include <rmr/rmr.h>
#include <rmr/ring_inline.h>

char* rmr_fib( char* fname );
int rmr_has_str( char const* buf, char const* str, char sep, int max );
int rmr_tokenise( char* buf, char** tokens, int max, char sep );
void* rmr_mk_ring( int size );
void rmr_ring_free( void* vr );

static inline void* rmr_ring_extract( void* vr )
static inline int rmr_ring_insert( void* vr, void* new_data )

DESCRIPTION

These functions support the RMR library, and are made available to user applications as some (e.g. route table generators) might need and/or want to make use of them. The rmr_fib function accepts a file name and reads the entire file into a single buffer. The intent is to provide an easy way to load a static route table without a lot of buffered I/O hoops.

The rmr_has_str function accepts a buffer containing a set of delimited tokens (e.g. foo,bar,goo) and returns true if the target string, str, matches one of the tokens. The sep parameter provides the separation character in the buffer (e.g a comma) and max indicates the maximum number of tokens to split the buffer into before checking.

The rmr_tokenise function is a simple tokeniser which splits buf into tokens at each occurrence of sep. Multiple occurrences of the separator character (e.g. a,,b) result in a nil token. Pointers to the tokens are placed into the tokens array provided by the caller which is assumed to have at least enough space for max entries.

The rmr_mk_ring function creates a buffer ring with size entries.

The rmr_ring_free function accepts a pointer to a ring context and frees the associated memory.

The rmr_ring_insert and rmr_ring_extract functions are provided as static inline functions via the rmr/ring_inline.h header file. These functions both accept the ring context returned by mk_ring, and either insert a pointer at the next available slot (tail) or extract the data at the head.

RETURN VALUES

The following are the return values for each of these functions.

The rmr_fib function returns a pointer to the buffer containing the contents of the file. The buffer is terminated with a single nil character (0) making it a legitimate C string. If the file was empty or nonexistent, a buffer with an immediate nil character. If it is important to the calling programme to know if the file was empty or did not exist, the caller should use the system stat function call to make that determination.

The rmr_has_str function returns 1 if buf contains the token referenced by &ita and false (0) if it does not. On error, a -1 value is returned and errno is set accordingly.

The rmr_tokenise function returns the actual number of token pointers placed into tokens

The rmr_mk_ring function returns a void pointer which is the context for the ring.

The rmr_ring_insert function returns 1 if the data was successfully inserted into the ring, and 0 if the ring is full and the pointer could not be deposited.

The rmr_ring_extract will return the data which is at the head of the ring, or NULL if the ring is empty.

ERRORS

Not many of these functions set the value in errno, however the value may be one of the following:

INVAL

Parameter(s) passed to the function were not valid.

EXAMPLE

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3),

Man Page: rmr_torcv_msg

RMR LIBRARY FUNCTIONS

NAME

rmr_torcv_msg

SYNOPSIS

#include <rmr/rmr.h>

rmr_mbuf_t* rmr_torcv_msg( void* vctx, rmr_mbuf_t* old_msg, int ms_to );

DESCRIPTION

The rmr_torcv_msg function will pause for ms_to milliseconds waiting for a message to arrive. If a message arrives before the timeout expires the message buffer returned will have a status of RMR_OK and the payload will contain the data received. If the timeout expires before the message is received, the status will have the value RMR_ERR_TIMEOUT. When a received message is returned the message buffer will also contain the message type and length set by the sender. If messages were queued while waiting for the response to a previous invocation of rmr_call, the oldest message is removed from the queue and returned without delay.

The vctx pointer is the pointer returned by the rmr_init function. Old_msg is a pointer to a previously used message buffer or NULL. The ability to reuse message buffers helps to avoid alloc/free cycles in the user application. When no buffer is available to supply, the receive function will allocate one.

RETURN VALUE

The function returns a pointer to the rmr_mbuf_t structure which references the message information (state, length, payload), or a nil pointer in the case of an extreme error.

ERRORS

The state field in the message buffer will be one of the following:

RMR_OK	The message buffer (payload) references the received data.
RMR_ERR_INITFAILED	The first call to this function must initialise an underlying system notification mechanism. On failure, this error is returned and errno will have the system error status set. If this function fails to initialise, the poll mechanism, it is likely that message receives will never be successful.
RMR_ERR_TIMEOUT	The timeout expired before a complete message was received. All other fields in the message buffer are not valid.
RMR_ERR_EMPTY	A message was received, but it had no payload. All other fields in the message buffer are not valid.

Upon return the system error number, errno might be set with a value that can help to explain the meaning of the state indicated in the message. The following are possible:

INVAL	Parameter(s) passed to the function were not valid.
EBADF	The underlying message transport is unable to process the request.
ENOTSUP	The underlying message transport is unable to process the request.
EFSM	The underlying message transport is unable to process the request.
EAGAIN	The underlying message transport is unable to process the request.
EINTR	The underlying message transport is unable to process the request.
ETIMEDOUT	The underlying message transport is unable to process the request.
ETERM	The underlying message transport is unable to process the request.

EXAMPLE

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_init(3), rmr_payload_size(3), rmr_rcv_msg(3), rmr_send_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3)

Man Page: rmr_trace_ref

RMR LIBRARY FUNCTIONS

NAME

rmr_trace_ref

SYNOPSIS

#include <rmr/rmr.h>

int rmr_trace_ref( rmr_mbuf_t* mbuf, int* sizeptr )

DESCRIPTION

The rmr_trace_ref function returns a pointer to the trace area in the message, and optionally populates the user programme supplied size integer with the trace area size, if sizeptr is not nil.

RETURN VALUE

On success, a void pointer to the trace area of the message is returned. A nil pointer is returned if the message has no trace data area allocated, or if the message itself is invalid.

SEE ALSO

rmr_alloc_msg(3), rmr_tralloc_msg(3), rmr_bytes2xact(3), rmr_bytes2meid(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_get_trlen(3), rmr_init(3), rmr_init_trace(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_str2meid(3), rmr_str2xact(3), rmr_wh_open(3), rmr_wh_send_msg(3), rmr_set_trace(3)

Man Page: rmr_tralloc_msg

RMR LIBRARY FUNCTIONS

NAME

rmr_tralloc_msg

SYNOPSIS

#include <rmr/rmr.h>

rmr_mbuf_t* rmr_tralloc_msg( void* vctx, int size,
                             int trace_size, unsigned const char *tr_data );

DESCRIPTION

The rmr_tralloc_msg function is used to allocate a buffer which the user programme can write into and then send through the library. The buffer is allocated such that sending it requires no additional copying from the buffer as it passes through the underlying transport mechanism.

The size parameter is used to set the payload length in the message. If it is 0, then the default size supplied on the rmr_init call will be used. In addition to allocating the payload, a space in the buffer is reserved for trace data (tr_size bytes), and the bytes pointed to by tr_data are copied into that portion of the message. The vctx parameter is the void context pointer that was returned by the rmr_init function.

The pointer to the message buffer returned is a structure which has some user application visible fields; the structure is described in rmr.h, and is illustrated below.

typedef struct {
    int state;
    int mtype;
    int len;
    unsigned char* payload;
    unsigned char* xaction;
} rmr_mbuf_t;

Where:

state	Is the current buffer state. Following a call to rmr_send_msg the state indicates whether the buffer was successfully sent which determines exactly what the payload points to. If the send failed, the payload referenced by the buffer is the message that failed to send (allowing the application to attempt a retransmission). When the state is a_OK the buffer represents an empty buffer that the application may fill in in preparation to send.
mtype	When sending a message, the application is expected to set this field to the appropriate message type value (as determined by the user programme). Upon send this value determines how the a library will route the message. For a buffer which has been received, this field will contain the message type that was set by the sending application.
len	The application using a buffer to send a message is expected to set the length value to the actual number of bytes that it placed into the message. This is likely less than the total number of bytes that the message can carry. For a message buffer that is passed to the application as the result of a receive call, this will be the value that the sending application supplied and should indicate the number of bytes in the payload which are valid.
payload	The payload is a pointer to the actual received data. The user programme may read and write from/to the memory referenced by the payload up until the point in time that the buffer is used on a rmr_send, rmr_call or rmr_reply function call. Once the buffer has been passed back to a a library function the user programme should NOT make use of the payload pointer.
xaction	The xaction field is a pointer to a fixed sized area in the message into which the user may write a transaction ID. The ID is optional with the exception of when the user application uses the rmr_call function to send a message and wait for the reply; the underlying processing expects that the matching reply message will also contain the same data in the xaction field.

RETURN VALUE

The function returns a pointer to a rmr_mbuf structure, or NULL on error.

ERRORS

ENOMEM

Unable to allocate memory.

SEE ALSO

rmr_alloc_msg(3), rmr_mbuf(3) rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_init_trace(3), rmr_get_trace(3), rmr_get_trlen(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_set_trace(3)

Man Page: rmr_wh_call

RMR LIBRARY FUNCTIONS

NAME

rmr_wh_call

SYNOPSIS

#include <rmr/rmr.h>

rmr_mbuf_t* rmr_wh_call( void* vctx, rmr_whid_t whid, rmr_mbuf_t* msg, int call_id, int max_wait )

DESCRIPTION

The rmr_wh_call function accepts a message buffer (msg) from the user application and attempts to send it using the wormhole ID provided (whid). If the send is successful, the call will block until either a response message is received, or the max_wait number of milliseconds has passed. In order for the response to be recognised as a response, the remote process must use rmr_rts_msg() to send their response.

Like rmr_wh_send_msg, this function attempts to send the message directly to a process at the other end of a wormhole which was created with rmr_wh_open(). When sending message via wormholes, the normal RMR routing based on message type is ignored, and the caller may leave the message type unspecified in the message buffer (unless it is needed by the receiving process). The call_id parameter is a number in the range of 2 through 255 and is used to identify the calling thread in order to properly match a response message when it arrives. Providing this value, and ensuring the proper uniqueness, is the responsibility of the user application and as such the ability to use the rmr_wh_call() function from potentially non-threaded concurrent applications (such as Go’s goroutines) is possible.

Retries

The send operations in RMR will retry soft send failures until one of three conditions occurs:

• The message is sent without error

• The underlying transport reports a hard failure

• The maximum number of retry loops has been attempted

A retry loop consists of approximately 1000 send attempts without any intervening calls to sleep() or usleep(). The number of retry loops defaults to 1, thus a maximum of 1000 send attempts is performed before returning to the user application. This value can be set at any point after RMR initialisation using the rmr_set_stimeout() function allowing the user application to completely disable retires (set to 0), or to increase the number of retry loops.

Transport Level Blocking

The underlying transport mechanism used to send messages is configured in non-blocking mode. This means that if a message cannot be sent immediately the transport mechanism will not pause with the assumption that the inability to send will clear quickly (within a few milliseconds). This means that when the retry loop is completely disabled (set to 0), that the failure to accept a message for sending by the underlying mechanisms (software or hardware) will be reported immediately to the user application.

It should be noted that depending on the underlying transport mechanism being used, it is extremely likely that retry conditions will happen during normal operations. These are completely out of RMR’s control, and there is nothing that RMR can do to avoid or mitigate these other than by allowing RMR to retry the send operation, and even then it is possible (e.g., during connection reattempts), that a single retry loop is not enough to guarantee a successful send.

RETURN VALUE

On success, new message buffer, with the payload containing the response from the remote endpoint is returned. The state in this buffer will reflect the overall send operation state and should be RMR_OK.

If a message is returned with a state which is anything other than RMR_OK, the indication is that the send was not successful. The user application must check the state and determine the course of action. If the return value is NULL, no message, the indication is that there was no response received within the timeout (max_wait) period of time.

ERRORS

The following values may be passed back in the state field of the returned message buffer.

RMR_ERR_WHID	The wormhole ID passed in was not associated with an open wormhole, or was out of range for a valid ID.
RMR_ERR_NOWHOPEN	No wormholes exist, further attempt to validate the ID are skipped.
RMR_ERR_BADARG	The message buffer pointer did not refer to a valid message.
RMR_ERR_NOHDR	The header in the message buffer was not valid or corrupted.

EXAMPLE

The following is a simple example of how the a wormhole is created (rmr_wh_open) and then how rmr_wh_send_msg function is used to send messages. Some error checking is omitted for clarity.

#include <rmr/rmr.h>    // system headers omitted for clarity

int main() {
   rmr_whid_t whid = -1;   // wormhole id for sending
   void* mrc;      //msg router context
        int i;
   rmr_mbuf_t*  sbuf;      // send buffer
   int     count = 0;
   int     norm_msg_size = 1500;    // most messages fit in this size

   mrc = rmr_init( "43086", norm_msg_size, RMRFL_NONE );
   if( mrc == NULL ) {
      fprintf( stderr, "[FAIL] unable to initialise RMR environment\\n" );
      exit( 1 );
   }

   while( ! rmr_ready( mrc ) ) {        // wait for routing table info
      sleep( 1 );
   }

   sbuf = rmr_alloc_msg( mrc, 2048 );

   while( 1 ) {
     if( whid < 0 ) {
       whid = rmr_wh_open( mrc, "localhost:6123" );  // open fails if endpoint refuses conn
          if( RMR_WH_CONNECTED( wh ) ) {
           snprintf( sbuf->payload, 1024, "periodic update from sender: %d", count++ );
           sbuf->len =  strlen( sbuf->payload );
           sbuf = rmr_wh_call( mrc, whid, sbuf, 1000 );        // expect a response in 1s or less
           if( sbuf != NULL && sbuf->state = RMR_OK ) {
             sprintf( stderr, "response: %s\\n", sbuf->payload );    // assume they sent a string
           } else {
             sprintf( stderr, "response not received, or send error\\n" );
           }
        }
      }

      sleep( 5 );
   }
}

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_payload_size(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_set_stimeout(3), rmr_wh_open(3), rmr_wh_close(3), rmr_wh_state(3)

Man Page: rmr_wh_close

RMR LIBRARY FUNCTIONS

NAME

rmr_wh_close

SYNOPSIS

#include <rmr/rmr.h>

void rmr_wh_close( void* vctx, rmr_whid_t whid )

DESCRIPTION

The rmr_wh_close function closes the wormhole associated with the wormhole id passed in. Future calls to rmr_wh_send_msg with this ID will fail.

The underlying TCP connection to the remote endpoint is not closed as this session may be required for regularly routed messages (messages routed based on message type). There is no way to force a TCP session to be closed at this point in time.

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_wh_open(3), rmr_wh_send_msg(3)

Man Page: rmr_wh_open

RMR LIBRARY FUNCTIONS

NAME

rmr_wh_open

SYNOPSIS

#include <rmr/rmr.h>

rmr_whid_t rmr_wh_open( void* vctx, char* target )

DESCRIPTION

The rmr_wh_open function creates a direct link for sending, a wormhole, to another RMR based process. Sending messages through a wormhole requires that the connection be established overtly by the user application (via this function), and that the ID returned by rmr_wh_open be passed to the rmr_wh_send_msg function.

Vctx is the RMR void context pointer that was returned by the rmr_init function. Target is the name and port, or IP-address and port, combination for the process that the wormhole should be connected to. For example, “localhost:6123”.

When invoked, this function immediately attempts to connect to the target process. If the connection cannot be established, an error is returned to the caller, and no direct messages can be sent to the target. Once a wormhole is connected, the underlying transport mechanism (e.g. NNG) will provide reconnects should the connection be lost, however the handling of messages sent when a connection is broken is undetermined as each underlying transport mechanism may handle buffering and retries differently.

RETURN VALUE

The rmr_wh_open function returns a type rmr_whid_t which must be passed to the rmr_wh_send_msg function when sending a message. The id may also be tested to determine success or failure of the connection by using the RMR_WH_CONNECTED macro and passing the ID as the parameter; a result of 1 indicates that the connection was established and that the ID is valid.

ERRORS

The following error values are specifically set by this RMR function. In some cases the error message of a system call is propagated up, and thus this list might be incomplete.

EINVAL	A parameter passed was not valid.
EACCESS	The user application does not have the ability to establish a wormhole to the indicated target (or maybe any target).
ECONNREFUSED	The connection was refused.

EXAMPLE

void*  rmc;
rmr_whid_t wh;

rmc = rmr_init( "43086", 4096, 0 ); // init context
wh = rmr_wh_open( rmc, "localhost:6123" );
if( !RMR_WH_CONNECTED( wh ) ) {
  fprintf( stderr, "unable to connect wormhole: %s\\n",
          strerror( errno ) );
}

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_wh_close(3), rmr_wh_send_msg(3), rmr_wh_state(3)

Man Page: rmr_wh_send_msg

RMR LIBRARY FUNCTIONS

NAME

rmr_wh_send_msg

SYNOPSIS

#include <rmr/rmr.h>

rmr_mbuf_t* rmr_wh_send_msg( void* vctx, rmr_whid_t id, rmr_mbuf_t* msg )

DESCRIPTION

The rmr_wh_send_msg function accepts a message buffer from the user application and attempts to send it using the wormhole ID provided (id). Unlike rmr_send_msg, this function attempts to send the message directly to a process at the other end of a wormhole which was created with rmr_wh_open(). When sending message via wormholes, the normal RMR routing based on message type is ignored, and the caller may leave the message type unspecified in the message buffer (unless it is needed by the receiving process).

Vctx is the RMR void context pointer that was returned by the rmr_init function. The message buffer (msg) used to send is the same format as used for regular RMR send and reply to sender operations, thus any buffer allocated by these means, or calls to rmr_rcv_msg() can be passed to this function.

Retries

The send operations in RMR will retry soft send failures until one of three conditions occurs:

• The message is sent without error

• The underlying transport reports a hard failure

• The maximum number of retry loops has been attempted

A retry loop consists of approximately 1000 send attempts without any intervening calls to sleep() or usleep(). The number of retry loops defaults to 1, thus a maximum of 1000 send attempts is performed before returning to the user application. This value can be set at any point after RMR initialisation using the rmr_set_stimeout() function allowing the user application to completely disable retires (set to 0), or to increase the number of retry loops.

Transport Level Blocking

The underlying transport mechanism used to send messages is configured in non-blocking mode. This means that if a message cannot be sent immediately the transport mechanism will not pause with the assumption that the inability to send will clear quickly (within a few milliseconds). This means that when the retry loop is completely disabled (set to 0), that the failure to accept a message for sending by the underlying mechanisms (software or hardware) will be reported immediately to the user application.

It should be noted that depending on the underlying transport mechanism being used, it is extremely likely that retry conditions will happen during normal operations. These are completely out of RMR’s control, and there is nothing that RMR can do to avoid or mitigate these other than by allowing RMR to retry the send operation, and even then it is possible (e.g., during connection reattempts), that a single retry loop is not enough to guarantee a successful send.

RETURN VALUE

On success, a new message buffer, with an empty payload, is returned for the application to use for the next send. The state in this buffer will reflect the overall send operation state and should be RMR_OK.

If the state in the returned buffer is anything other than RMR_OK, the user application may need to attempt a retransmission of the message, or take other action depending on the setting of errno as described below.

In the event of extreme failure, a nil pointer is returned. In this case the value of errno might be of some use, for documentation, but there will be little that the user application can do other than to move on.

ERRORS

The following values may be passed back in the state field of the returned message buffer.

RMR_ERR_WHID	The wormhole ID passed in was not associated with an open wormhole, or was out of range for a valid ID.
RMR_ERR_NOWHOPEN	No wormholes exist, further attempt to validate the ID are skipped.
RMR_ERR_BADARG	The message buffer pointer did not refer to a valid message.
RMR_ERR_NOHDR	The header in the message buffer was not valid or corrupted.

The following values may be assigned to errno on failure.

INVAL	Parameter(s) passed to the function were not valid, or the underlying message processing environment was unable to interpret the message.
ENOKEY	The header information in the message buffer was invalid.
ENXIO	No known endpoint for the message could be found.
EMSGSIZE	The underlying transport refused to accept the message because of a size value issue (message was not attempted to be sent).
EFAULT	The message referenced by the message buffer is corrupt (nil pointer or bad internal length).
EBADF	Internal RMR error; information provided to the message transport environment was not valid.
ENOTSUP	Sending was not supported by the underlying message transport.
EFSM	The device is not in a state that can accept the message.
EAGAIN	The device is not able to accept a message for sending. The user application should attempt to resend.
EINTR	The operation was interrupted by delivery of a signal before the message was sent.
ETIMEDOUT	The underlying message environment timed out during the send process.
ETERM	The underlying message environment is in a shutdown state.

EXAMPLE

The following is a simple example of how the a wormhole is created (rmr_wh_open) and then how rmr_wh_send_msg function is used to send messages. Some error checking is omitted for clarity.

#include <rmr/rmr.h>    // system headers omitted for clarity

int main() {
   rmr_whid_t whid = -1;   // wormhole id for sending
   void* mrc;      //msg router context
        int i;
   rmr_mbuf_t*  sbuf;      // send buffer
   int     count = 0;
   int     norm_msg_size = 1500;  // most msg fit in this size

   mrc = rmr_init( "43086", norm_msg_size, RMRFL_NONE );
   if( mrc == NULL ) {
      fprintf( stderr, "[FAIL] unable to initialise RMR environment\\n" );
      exit( 1 );
   }

   while( ! rmr_ready( mrc ) ) {        // wait for routing table info
      sleep( 1 );
   }

   sbuf = rmr_alloc_msg( mrc, 2048 );

   while( 1 ) {
     if( whid < 0 ) {
       whid = rmr_wh_open( mrc, "localhost:6123" );  // open fails if endpoint refuses conn
          if( RMR_WH_CONNECTED( wh ) ) {
           snprintf( sbuf->payload, 1024, "periodic update from sender: %d", count++ );
           sbuf->len =  strlen( sbuf->payload );
           sbuf = rmr_wh_send_msg( mrc, whid, sbuf );
        }
     }

     sleep( 5 );
   }
}

SEE ALSO

rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), rmr_payload_size(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_set_stimeout(3), rmr_wh_open(3), rmr_wh_close(3), rmr_wh_state(3)

Man Page: rmr_wh_state

RMR LIBRARY FUNCTIONS

NAME

rmr_wh_state

SYNOPSIS

#include <rmr/rmr.h>

int rmr_wh_state( void* vctx, rmr_whid_t whid )

DESCRIPTION

The rmr_wh_state function will return the current state of the connection associated with the given wormhole (whid). The return value indicates whether the connection is open (RMR_OK), or closed (any other return value).

When using some transport mechanisms (e.g. NNG), it may not be possible for RMR to know the actual state and the connection may always be reported as “open.”

RETURN

The following values are potential return values.

RMR_OK	The wormhole ID is valid and the connection is “open.”
RMR_ERR_WHID	THe wormhole ID passed into the function was not valid.
RMR_ERR_NOENDPT	The wormhole is not open (not connected).
RMR_ERR_BADARG	The context passed to the function was nil or invalid.
RMR_ERR_NOWHOPEN	Wormholes have not been initialised (no wormhole open call has been made).

SEE ALSO

rmr_wh_open(3), rmr_wh_send_msg(3), rmr_wh_close(3)

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