*********************************
omjournal: Systemd Journal Output
*********************************

===========================  ===========================================================================
**Module Name:**             **omjournal**
**Author:**                  `Rainer Gerhards <https://rainer.gerhards.net/>`_ <rgerhards@adiscon.com>
===========================  ===========================================================================


Purpose
=======

This module provides native support for logging to the systemd journal.


Configuration Parameters
========================

.. note::

   Parameter names are case-insensitive.


Action Parameters
-----------------

Template
^^^^^^^^

.. csv-table::
   :header: "type", "default", "mandatory", "|FmtObsoleteName| directive"
   :widths: auto
   :class: parameter-table

   "word", "none", "no", "none"

Template to use when submitting messages.

By default, rsyslog will use the incoming %msg% as the MESSAGE field
of the journald entry, and include the syslog tag and priority.

You can override the default formatting of the message, and include
custom fields with a template. Complex fields in the template
(eg. json entries) will be added to the journal as json text. Other
fields will be coerced to strings.

Journald requires that you include a template parameter named MESSAGE.

namespace
^^^^^^^^^

.. csv-table::
   :header: "type", "default", "mandatory", "|FmtObsoleteName| directive"
   :widths: auto
   :class: parameter-table

   "word", "none", "no", "none"

Starting from systemd v256, the journal supports namespaces. This allows
you to write to a specific namespace in the journal, which can be useful
for isolating logs from different applications or components.
However, this feature does not support templates yet.

Examples
========

Example 1
---------

The following sample writes all syslog messages to the journal with a
custom EVENT_TYPE field and to override journal's default *identifier* (which by default will be ``rsyslogd``):

.. code-block:: shell

   module(load="omjournal")

   template(name="journal" type="list") {
     # Emulate default journal fields
     property(name="msg" outname="MESSAGE")
     property(name="timestamp" outname="SYSLOG_TIMESTAMP")
     property(name="syslogfacility" outname="SYSLOG_FACILITY")
     property(name="syslogseverity" outname="PRIORITY")

     # Custom fields
     constant(value="strange" outname="EVENT_TYPE")
     constant(value="router" outname="SYSLOG_IDENTIFIER")
   }

   action(type="omjournal" template="journal")


Example 2
---------

The `subtree` template is a better fit for structured outputs like this, allowing arbitrary expressions for the destination journal fields using `set` & `reset` directives in *rulsets*.  For instance, here the captured *tags* are translated with `Lookup Tables`
(to facilitae filtering with ``journalctl -t <TAG>``):

.. code-block:: shell

   module(load="omjournal")

   template(name="journal-subtree" type="subtree" subtree="$!")

   lookup_table("tags", ...)

   ruleset(name="journal") {
     # Emulate default journal fields
     set $!MESSAGE = $msg;
     set $!SYSLOG_TIMESTAMP = $timestamp;
     set $!SYSLOG_FACILITY = $syslogfacility;
     set $!PRIORITY = $syslogseverity

     set $!SYSLOG_IDENTIFIER = lookup("tags", $hostname-ip);

     action(type="omjournal" template="journal-subtree")
   }


Example 3
---------

The following example shows how to use the namespace feature to filter logs
by facility and write them to different namespaces in the journal. This is useful for journal isolation and classification:

.. code-block:: shell

   module(load="imtcp")
   module(load="omjournal")

   # Each tcp input will trigger the filter ruleset
   input(type="imtcp" port="80" ruleset="output-filter")

   # Filter logs by facility into two different namespaces audit and application
   ruleset(name="output-filter") {
      if ($syslogfacility == 13) then {
         action(type="omjournal" namespace="audit-journal-namespace")
      }
      if ($syslogfacility == 16) then {
         action(type="omjournal" namespace="application-journal-namespace")
      }
   }
   # If you specify a namespace, you must not specify a template. If you do, the action will fail with an error message.
   # namespaces have to be created before use.
