feat: How to stream runtime logs as JSON ouptut to a remote server (#…

…2952)

Add a section on logging page to explain how to configure log4j to
stream the log as JSON output to a remote server

---------

Co-authored-by: Vincent HEMERY <vincent.hemery@bonitasoft.com>

modules/setup-dev-environment/pages/logging.adoc

@@ -46,6 +46,63 @@ Here is an example of the Log4j2 configuration for the logger used in the exampl
 <Logger name="org.bonitasoft.groovy.script" level="TRACE"/>
 ----
 
+
+==== Use JSON format for logs
+
+The default configuration contains an unused `Console-JSON` appender which formats logs as JSON.
+
+[source, xml]
+----
+    <Appenders>
+        <!-- use json logger if json output is required -->
+        <Console name="Console-JSON" target="SYSTEM_OUT">
+            <JSONLayout compact="true" eventEol="true" properties="true" stacktraceAsString="true">
+                <KeyValuePair key="timestamp" value="$${date:yyyy-MM-dd'T'HH:mm:ss.SSSZ}"/>
+            </JSONLayout>
+        </Console>
+        <!-- [...] -->
+    </Appenders>
+----
+
+To use it, you can update the `AppenderRef` in the `Loggers` block or add a new one.
+
+[source, xml]
+----
+    <Loggers>
+        <Root level="INFO">
+            <AppenderRef ref="Console-JSON"/>
+        </Root>
+    </Loggers>
+----
+
+==== Stream logs to a remote server
+
+You need to declare a Socket appender in `log4j-appenders.xml` to stream to a remote server. You can choose to use Socket with various formats, such as JSONLayout or PatternLayout.
+
+As example, this configuration is used to stream JSON-formatted log entries to a remote server, such as Logstash, for further processing and analysis.
+
+[source, xml]
+----
+<Socket name="runtimeLogSocket" host="<host>" port="<port>">
+    <JSONLayout compact="true" eventEol="true" properties="true" stacktraceAsString="true">
+        <KeyValuePair key="timestamp" value="$${date:yyyy-MM-dd'T'HH:mm:ss.SSSZ}"/>
+    </JSONLayout>
+</Socket>
+----
+
+Then, do not forget to reference this new appender in `Loggers` block:
+
+[source, xml]
+----
+    <Loggers>
+        <Root level="INFO">
+            <!-- [...] -->
+            <AppenderRef ref="runtimeLogSocket"/> <!-- Add this AppenderRef -->
+            <!-- [...] -->
+        </Root>
+    </Loggers>
+----
+
 === Bonita Studio
 
 To change the Bonita Studio log level (usually to debug Studio), go to the Studio installation folder, configuration directory, and edit the `config.ini` file. You need to set the property `eclipse.log.level` to one of the following values: INFO, WARNING or ERROR.