+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:
+
+
+ .. list-table::
+ :widths: auto
+ :header-rows: 0
+ :class: borderless
+
+ * - **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:
+
+
+ .. list-table::
+ :widths: auto
+ :header-rows: 0
+ :class: borderless
+
+ * - **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_STASH_RT**
+ -
+ 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_RT`` variable value and adding a ``.stash`` suffix
+ to the filename so as not to overwrite the static table.
+
+ * - **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.
+
+
+
+There are other, non-RMR, variables which may exist and are
+used by RMR. These variable names are not under the control
+of RMR, so they are subject to change without potentiallyb
+being reflected in either RMR's code, or this document. The
+following is a list of these environment variables.
+
+
+ .. list-table::
+ :widths: auto
+ :header-rows: 0
+ :class: borderless
+
+ * - **ALARM_MANAGER_SERVICE_NAME**
+ -
+ This is the DNS name, or IP address, of the process which is
+ listening for RMR alarm messages. If this variable is
+ missing, ``service-ricplt-alarmmanager-rmr`` is assumed.
+
+ * - **ALARM_MANAGER_SERVICE_PORT**
+ -
+ This is the port that the alarm manager is using to accept
+ RMR messages. If the environment variable is missing the
+ value ``4560`` is assumed.
+
+
+
+
+Logging and Alarms
+------------------
+
+As with nearly all UNIX libraries, errors, warnings and
+informational messages are written in plain text to the
+standard error device (stderr). All RMR messages are prefixed
+with the current time (in milliseconds past the standard UNIX
+epoch), the process ID, and a severity indicator. RMR
+messages are written with one of three severity strings:
+
+
+ .. list-table::
+ :widths: auto
+ :header-rows: 0
+ :class: borderless
+
+ * - **[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.