.. include:: /../getting_started/vars.rst

.. _section-telemetry-logs:

Logs 
====

*Observability Framework* stores the log messages generated by |Connext| 
applications and stores them in a third-party backend for analysis. 

Log messages generated before *Observability Library* is enabled are not 
stored.

Each log message is divided into three parts to facilitate analysis, as
illustrated in :numref:`FigureLogMessage`.

.. figure:: ../static/log-message-format.png
    :figwidth: 90 %
    :alt: Log Message Format
    :name: FigureLogMessage
    :align: center

    Log Message Format

This release only supports MIDDLEWARE as a Syslog Facility. Future releases
will also provide support for SECURITY, SERVICE, and USER.

Syslog Level can have the following values: EMERGENCY, ERROR, WARNING,
INFORMATIONAL, or DEBUG.

The mapping between |Connext| Log Levels and Syslog Levels is as follows:

.. list-table:: Log Level Mapping
    :name: TableLogLevelMapping
    :widths: 40 20 40
    :header-rows: 1

    * - NDDS_Config_LogLevel
      - Syslog Level
      - Minimum Syslog Verbosity that lets the message pass through
    * - NDDS_CONFIG_LOG_LEVEL_FATAL_ERROR
      - EMERGENCY
      - ERROR
    * - NDDS_CONFIG_LOG_LEVEL_ERROR
      - ERROR
      - ERROR
    * - NDDS_CONFIG_LOG_LEVEL_WARNING
      - WARNING
      - WARNING
    * - NDDS_CONFIG_LOG_LEVEL_STATUS_LOCAL
      - INFORMATIONAL
      - INFORMATIONAL
    * - NDDS_CONFIG_LOG_LEVEL_STATUS_REMOTE
      - INFORMATIONAL
      - INFORMATIONAL
    * - NDDS_CONFIG_LOG_LEVEL_DEBUG
      - DEBUG
      - DEBUG

.. note:: 

   In the current release, it is not possible to filter only emergency
   (NDDS_CONFIG_LOG_LEVEL_FATAL_ERROR) log messages from *Observability
   Dashboards*.

The Activity Context provides context for the log message associated with 
it. The information provided by the activity context includes a sequence 
of activities and resources to which the activities apply. Comparing the 
Activity Context to traces and spans in OpenTelemetry, you can think of the 
activity context as a trace and the individual activities within the 
activity context as spans within the trace. For additional information 
on the Activity Context, see :link_connext_dds_pro_um_up_one:`Format of Logged 
Messages <#users_manual/Format_of_Logged_Messages.htm#Activity>`
in the *RTI Connext Core Libraries User's Manual*.

The Activity Context is available by default in all log messages generated 
by a |Connext| application. However, you can disable this information by 
using the APIs in the C language binding: see :link_connext_dds_api_c_up_one:`NDDS_Config_Logger_set_print_format <group__DDSLoggingModule.html#ga10e8404356097ba8708417b17dea04a8>`
and :link_connext_dds_api_c_up_one:`NDDS_Config_Logger_set_print_format_by_log_level <group__DDSLoggingModule.html#ga10e8404356097ba8708417b17dea04a8>`. 
The same APIs are available in other language bindings.