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+***********************************
+Fields Extraction Module (mmfields)
+***********************************
+
+===========================  ===========================================================================
+**Module Name:**             **mmfields**
+**Author:**                  `Rainer Gerhards <https://rainer.gerhards.net/>`_ <rgerhards@adiscon.com>
+**Available since:**         7.5.1
+===========================  ===========================================================================
+
+
+Purpose
+=======
+
+The mmfield module permits to extract fields. It is an alternate to
+using the property replacer field extraction capabilities. In contrast
+to the property replacer, all fields are extracted as once and stored
+inside the structured data part (more precisely: they become Lumberjack
+[JSON] properties).
+
+Using this module is of special advantage if a field-based log format is
+to be processed, like for example CEF **and** either a large number
+of fields is needed or a specific field is used multiple times inside
+filters. In these scenarios, mmfields potentially offers better
+performance than the property replacer of the RainerScript field
+extraction method. The reason is that mmfields extracts all fields as
+one big sweep, whereas the other methods extract fields individually,
+which requires multiple passes through the same data. On the other hand,
+adding field content to the rsyslog property dictionary also has some
+overhead, so for high-performance use cases it is suggested to do some
+performance testing before finally deciding which method to use. This is
+most important if only a smaller subset of the fields is actually
+needed.
+
+In any case, mmfields provides a very handy and easy to use way to parse
+structured data into a it's individual data items. Again, a primary use
+case was support for CEF (Common Event Format), which is made extremely
+easy to do with this module.
+
+This module is implemented via the action interface. Thus it can be
+conditionally used depending on some prerequisites.
+
+ 
+Configuration Parameters
+========================
+
+.. note::
+
+   Parameter names are case-insensitive.
+
+
+Action Parameters
+-----------------
+
+separator
+^^^^^^^^^
+
+.. csv-table::
+   :header: "type", "default", "mandatory", "|FmtObsoleteName| directive"
+   :widths: auto
+   :class: parameter-table
+
+   "char", ",", "no", "none"
+
+This is the character used to separate fields. Currently, only a
+single character is permitted, while the RainerScript method permits
+to specify multi-character separator strings. For CEF, this is not
+required. If there is actual need to support multi-character
+separator strings, support can relatively easy be added. It is
+suggested to request it on the rsyslog mailing list, together with
+the use case - we intend to add functionality only if there is a real
+use case behind the request (in the past we too-often implemented
+things that actually never got used).
+The fields are named f\ *nbr*, where *nbr* is the field number
+starting with one and being incremented for each field.
+
+
+jsonRoot
+^^^^^^^^
+
+.. csv-table::
+   :header: "type", "default", "mandatory", "|FmtObsoleteName| directive"
+   :widths: auto
+   :class: parameter-table
+
+   "string", "!", "no", "none"
+
+This parameters specifies into which json path the extracted fields
+shall be written. The default is to use the json root object itself.
+
+
+Examples
+========
+
+Parsing messages and writing them to file
+-----------------------------------------
+
+This is a very simple use case where each message is parsed. The default
+separator character of comma is being used.
+
+.. code-block:: none
+
+   module(load="mmfields")
+   template(name="ftpl"
+            type="string"
+            string="%$!%\\n")
+   action(type="mmfields")
+   action(type="omfile"
+          file="/path/to/logfile"
+          template="ftpl")
+
+
+Writing into a specific json path
+---------------------------------
+
+The following sample is similar to the previous one, but this time the
+colon is used as separator and data is written into the "$!mmfields"
+json path.
+
+.. code-block:: none
+
+   module(load="mmfields")
+   template(name="ftpl"
+            type="string"
+            string="%$!%\\n")
+   action(type="mmfields"
+          separator=":"
+          jsonRoot="!mmfields")
+   action(type="omfile"
+          file="/path/to/logfile"
+          template="ftpl")
+