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new 82432570e8 Add documentation for `MessageRewritePolicy` (#4042)
82432570e8 is described below
commit 82432570e8bb9a67c32de51dc63ebcfcec939818
Author: Neelesh Mehar <[email protected]>
AuthorDate: Sun May 3 00:49:44 2026 +0530
Add documentation for `MessageRewritePolicy` (#4042)
Co-authored-by: Volkan Yazıcı <[email protected]>
---
.../ROOT/pages/manual/appenders/delegating.adoc | 46 ++++++++++++++--------
.../antora/modules/ROOT/pages/manual/layouts.adoc | 6 +++
2 files changed, 36 insertions(+), 16 deletions(-)
diff --git
a/src/site/antora/modules/ROOT/pages/manual/appenders/delegating.adoc
b/src/site/antora/modules/ROOT/pages/manual/appenders/delegating.adoc
index 7c783c5c49..6076fafa71 100644
--- a/src/site/antora/modules/ROOT/pages/manual/appenders/delegating.adoc
+++ b/src/site/antora/modules/ROOT/pages/manual/appenders/delegating.adoc
@@ -521,12 +521,12 @@
xref:plugin-reference.adoc#org-apache-logging-log4j_log4j-core_org-apache-loggin
Log4j Core provides three rewrite policies out-of-the-box:
[#MapRewritePolicy]
-`MapRewritePolicy`::
-+
+==== `MapRewritePolicy`
+
The `MapRewritePolicy` only modifies events that contain a
xref:manual/messages.adoc#MapMessage[`MapMessage`].
It allows adding or updating the keys of the `MapMessage`.
-+
+
[#MapRewritePolicy-attributes]
.`MapRewritePolicy` configuration attributes
[cols="1m,1,1,5"]
@@ -546,7 +546,7 @@ Update::
The rewrite policy will add to the `MapMessage` only entries corresponding to
existing keys.
|===
-+
+
[#MapRewritePolicy-elements]
.`MapRewritePolicy` nested elements
[cols="1m,1,4"]
@@ -561,20 +561,20 @@
xref:plugin-reference.adoc#org-apache-logging-log4j_log4j-core_org-apache-loggin
A list of map entries to add to the `MapMessage`.
|===
-+
+
xref:plugin-reference.adoc#org-apache-logging-log4j_log4j-core_org-apache-logging-log4j-core-appender-rewrite-MapRewritePolicy[{plugin-reference-marker}
Plugin reference for `MapRewritePolicy`]
[#PropertiesRewritePolicy]
-`PropertiesRewritePolicy`::
-+
+==== `PropertiesRewritePolicy`
+
The `PropertiesRewritePolicy` will add properties to the context data of the
log event.
-+
+
[NOTE]
====
Only the context data of the log event will be modified.
The contents of the xref:manual/thread-context.adoc[] will remain unchanged.
====
-+
+
[#PropertiesRewritePolicy-elements]
.`PropertiesRewritePolicy` nested elements
[cols="1m,1,4"]
@@ -591,22 +591,22 @@
xref:manual/configuration.adoc#lazy-property-substitution[runtime property subst
in the
xref:manual/lookups.adoc#global-context[_global context_].
|===
-+
+
xref:plugin-reference.adoc#org-apache-logging-log4j_log4j-core_org-apache-logging-log4j-core-appender-rewrite-PropertiesRewritePolicy[{plugin-reference-marker}
Plugin reference for `PropertiesRewritePolicy`]
[#LoggerNameLevelRewritePolicy]
-LoggerNameLevelRewritePolicy::
-+
+==== LoggerNameLevelRewritePolicy
+
You can use this policy to change the log level of loggers from third-party
libraries.
The `LoggerNameLevelRewritePolicy` will rewrite the level of log event for a
given logger name prefix.
-+
+
[WARNING]
====
The new log levels will only be used by the filter attached to the `Rewrite`
appender and those downstream of the appender.
Filters configured on loggers will use the previous levels.
See xref:manual/filters.adoc[] for more details on filtering
====
-+
+
[#LoggerNameLevelRewritePolicy-attributes]
.`LoggerNameLevelRewritePolicy` configuration attributes
[cols="1m,1,1,5"]
@@ -620,7 +620,7 @@ See xref:manual/filters.adoc[] for more details on filtering
The rewrite policy will only be applied to loggers with this logger name and
their children.
|===
-+
+
[#LoggerNameLevelRewritePolicy-elements]
.`LoggerNameLevelRewritePolicy` nested elements
[cols="1m,1,4"]
@@ -633,9 +633,23 @@ The rewrite policy will only be applied to loggers with
this logger name and the
Provides a mapping between old level names and new level names.
|===
-+
+
xref:plugin-reference.adoc#org-apache-logging-log4j_log4j-core_org-apache-logging-log4j-core-appender-rewrite-LoggerNameLevelRewritePolicy[{plugin-reference-marker}
Plugin reference for `LoggerNameLevelRewritePolicy`]
+[#ThirdPartyRewritePolicies]
+=== Third Party Rewrite Policies
+
+[WARNING]
+====
+These `Rewrite Policies` are provided by **third-party** vendors and are not
maintained by the https://logging.apache.org/[Apache Logging Services] project.
+====
+
+[#MessageRewritePolicy]
+==== `MessageRewritePolicy`
+
+The `MessageRewritePolicy` provided by
https://github.com/Neel1210/log4j-utils[log4j-utils] allows you to manipulate
the text of a log message before it is processed by a downstream appender.
+This is particularly useful for defining multiple regex-based replacement
rules to mask sensitive information (PII) within the log message as a
defensive-in-depth strategy.
+
[#RewriteAppender-examples]
=== Configuration example
diff --git a/src/site/antora/modules/ROOT/pages/manual/layouts.adoc
b/src/site/antora/modules/ROOT/pages/manual/layouts.adoc
index 7467de8d11..ab97c04793 100644
--- a/src/site/antora/modules/ROOT/pages/manual/layouts.adoc
+++ b/src/site/antora/modules/ROOT/pages/manual/layouts.adoc
@@ -51,6 +51,12 @@ If you want all your log events to be formatted in a certain
character encoding
include::partial$manual/layouts-location-information.adoc[]
+[#log-event-content]
+=== Log event content
+
+While layouts are responsible for formatting a log event into a string or byte
array, they do not typically modify the content of the event itself.
+You can use xref:manual/appenders/delegating.adoc#RewriteAppender[Rewrite
Appender] to modify the log event content to suit your needs; to inject
additional metadata, to mask sensitive information (such as PII) as a
defensive-in-depth strategy, etc.
+
[#collection]
== Collection
