doc/src/man/rmr.7.xfm

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==================================================================================
   Copyright (c) 2019 Nokia
   Copyright (c) 2018-2019 AT&T Intellectual Property.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
==================================================================================
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    Mnemonic    rmr.7.xfm
    Abstract    The manual page for the whole RMR library
    Author      E. Scott Daniels
    Date        29 January 2019
.fi

.gv e LIB lib
.im &{lib}/man/setup.im

&line_len(6i)

&h1(RMR Library)

&h2(NAME)
    RMR -- Ric Message Router Library

&h2(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.

&space
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.


&h3(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.

&space
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: &ital(rte) and
&ital(mse).

&space
A &ital(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.

&ex_start
    rte | 1 | app10:4560
&ex_end

&space
The second type of entry is &ital(mse).  This entry defines a message
type, an optional sender application, a subscription ID, and a
collection of endpoints. An example record appears next.
&ex_start
    mse | 1000,forwarder:43086 | 10 | app2:43086
&ex_end

&space
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.

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

&ex_start
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
&ex_end

&space
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:

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

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

&space
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 &cw(mme_del) record to the table.  The
following example illustrates how this might look:

&ex_start
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
&ex_end

&h3(Route Table Syntax)
The following illustrates the syntax for both types of route table entries.

&space
&ex_start
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
&ex_end

&space
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.

&h3(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.

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

&space
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.

&space
The optional <md5sum> on the &ital(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.


&h3(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.

.** the list of environment vars supported
.im &{lib}/man/env_var_list.im


&h2(SEE ALSO )
.ju off
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)
.ju on