Man Page: rmr¶
RMR – Ric Message Router Library
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
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. 184.108.40.206:8219), 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.
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.
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.
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.
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.
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_SVCis not defined.
RMR_CTL_PORTis 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).
RMR_CTL_PORTis 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_RTG_SVCbe defined. In the case where both variables are defined, RMR will behave exactly as is communicated with the variable’s values.
When RMR needs a new route table it will send a request once every
nseconds. The default value for
nis 5, but can be changed if this variable is set prior to invoking the process. Accepted values are between 1 and 300 inclusive.
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
portwhich 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
hostof the Route Manager process.
RMR_CTL_PORTvariable (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.
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.
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:
Off; no messages of any sort are written.
Only critical messages are written (default if this variable does not exist)
Errors and all messages written with a lower value.
Warnings and all messages written with a lower value.
Informational and all messages written with a lower value.
Debugging mode – all messages written, however this requires RMR to have been compiled with debugging support enabled.
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.
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).
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.
Names the file where RMR should write the latest update it receives from the source of route tables (generally Route Manager). This is meant to assist with debugging and/or troubleshooting when it is suspected that route information isn’t being sent and/or received correctly. If this variable is not given, RMR will save the last update using the
RMR_SEED_RTvariable value and adding a
.stashsuffix to the filename so as not to overwrite the static table.
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.
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.
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)