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    <properties>
        <title>JMX</title>
		<author email="remkop@yahoo.com">Remko Popma</author>
    </properties>

    <body>
      <section name="JMX">
        <p>
          Log4j 2 has built-in support for JMX.
          The StatusLogger, ContextSelector, and all LoggerContexts,
          LoggerConfigs and Appenders are instrumented with MBeans and can
          be remotely monitored and controlled.
        </p>
        <p>Also included is a simple client GUI that can be used to
        monitor the StatusLogger output, as well as to remotely reconfigure
        Log4j with a different configuration file, or to edit the
        current configuration directly.
        </p>
      </section>
      <section name="Enabling JMX">
        <a name="Enabling_JMX" />
        <p>JMX support is enabled by default. When Log4j initializes,
        the StatusLogger, ContextSelector, and all LoggerContexts,
          LoggerConfigs and Appenders are instrumented with MBeans.
        To disable JMX completely, and prevent these MBeans from being created,
        specify system property <tt>log4j2.disableJmx</tt> to <tt>true</tt> when you start
        the Java VM.
        </p>
		<subsection name="Local Monitoring and Management">
      <a name="Local" />
      <p>To perform local monitoring you don't need to specify any system
        properties. The JConsole tool that is included in the Java JDK can be
        used to monitor your application. Start JConsole by typing
        <code>${dollar}JAVA_HOME/bin/jconsole</code> in a command shell.
        For more details, see Oracle's documentation on
        <a href="https://docs.oracle.com/javase/7/docs/technotes/guides/management/jconsole.html">how to use JConsole</a>.</p>
        </subsection>
		<subsection name="Remote Monitoring and Management">
      <a name="Remote" />
      <p>To enable monitoring and management from remote systems, set the following system property when starting the Java VM.
		</p><p>
        <code>com.sun.management.jmxremote.port=portNum</code>
		</p><p>
        In the property above, <code>portNum</code> is the port number through
        which you want to enable JMX RMI connections.
        </p><p>
        For more details, see Oracle's documentation on
        <a href="https://docs.oracle.com/javase/7/docs/technotes/guides/management/agent.html#gdenl">Remote
        Monitoring and Management</a>.</p>
        </subsection>
		<subsection name="RMI impact on Garbage Collection">
      <a name="RMI_GC" />
      <p>
      	Be aware that RMI by default triggers a full GC every hour.
        See the <a href="https://docs.oracle.com/javase/7/docs/technotes/guides/rmi/sunrmiproperties.html">Oracle
        documentation</a> for the <code>sun.rmi.dgc.server.gcInterval</code> and <code>sun.rmi.dgc.client.gcInterval</code> properties.
        The default value of both properties is 3600000 milliseconds (one hour). Before Java 6, it was one minute.
		  </p><p>
		    The two sun.rmi arguments reflect whether your JVM is running in server or client mode. 
		    If you want to modify the GC interval time it may be best to specify both properties to ensure the argument is picked up by the JVM.
		  </p><p>
		    An alternative may be to disable explicit calls to <code>System.gc()</code> altogether with 
		    <code>-XX:+DisableExplicitGC</code>, or (if you are using the CMS or G1 collector)
		    add <code>-XX:+ExplicitGCInvokesConcurrent</code> to ensure the full GCs are done
		    concurrently in parallel with your application instead of forcing a stop-the-world collection.
      </p>
        </subsection>
      </section>
      <section name="Log4j Instrumented Components">
        <a name="Log4j_MBeans" />
        <p>The best way to find out which methods and attributes of the various
      Log4j components are accessible via JMX is to look at the
      <a href="../log4j-core/apidocs/org/apache/logging/log4j/core/jmx/package-summary.html"
      >Javadoc</a> or by exploring directly in JConsole.</p>
      <p>The screenshot below shows the Log4j MBeans in JConsole.</p>
      <p><img src="../images/jmx-jconsole-mbeans.png" alt="JConsole screenshot of the MBeans tab" /></p>
      </section>
      <section name="Client GUI">
        <a name="ClientGUI" />
        <p>Log4j includes a basic client GUI that can be used to
        monitor the StatusLogger output and to remotely modify the Log4j
        configuration. The client GUI can be run as a stand-alone application
        or as a JConsole plug-in.</p>
		<subsection name="Running the Client GUI as a JConsole Plug-in">
		<p>To run the Log4j JMX Client GUI as a JConsole Plug-in,
		start JConsole with the following command:
		</p>
		<p><code>${dollar}JAVA_HOME/bin/jconsole -pluginpath /path/to/log4j-api-${Log4jReleaseVersion}.jar:/path/to/log4j-core-${Log4jReleaseVersion}.jar:/path/to/log4j-jmx-gui-${Log4jReleaseVersion}.jar</code></p>
		<p>or on Windows:</p>
		<p><code>%JAVA_HOME%\bin\jconsole -pluginpath \path\to\log4j-api-${Log4jReleaseVersion}.jar;\path\to\log4j-core-${Log4jReleaseVersion}.jar;\path\to\log4j-jmx-gui-${Log4jReleaseVersion}.jar</code></p>
		<p>If you execute the above command and connect to your application,
		you will see an extra "Log4j 2" tab in the JConsole window.
		This tab contains the client GUI, with the StatusLogger selected.
		The screenshot below shows the StatusLogger panel in JConsole.
		</p>
        <p><img src="../images/jmx-jconsole-statuslogger.png" alt="JConsole screenshot of the StatusLogger display" /></p>
		</subsection>
		<subsection name="Remotely Editing the Log4j Configuration">
		<p>The client GUI also contains a simple editor that can be used
		to remotely change the Log4j configuration.
		</p><p>
		The screenshot below shows the configuration edit panel in JConsole.
		</p>
        <p><img src="../images/jmx-jconsole-editconfig.png" alt="JConsole screenshot of the configuration file editor" /></p>
        <p>The configuration edit panel provides two ways to modify
        the Log4j configuration: specifying a different configuration location
        URI, or modifying the configuration XML directly in the editor panel.</p>
        <p>If you specify a different configuration location URI and
        click the "Reconfigure from Location" button, the specified file
        or resource must exist and be readable by the application,
        or an error will occur and the configuration will not change.
        If an error occurred while processing the contents of the specified resource,
        Log4j will keep its original configuration, but the editor panel
        will show the contents of the file you specified. </p>
        <p>
        The text area showing the contents of the configuration file is
        editable, and you can directly modify the configuration in this
        editor panel. Clicking the "Reconfigure with XML below" button will
        send the configuration text to the remote application where it
        will be used to reconfigure Log4j on the fly.
        This will not overwrite any configuration file.
        Reconfiguring with text from the editor happens in memory only and
        the text is not permanently stored anywhere.
        </p>
		</subsection>
		<subsection name="Running the Client GUI as a Stand-alone Application">
      <a name="ClientStandAlone" />
      <p>To run the Log4j JMX Client GUI as a stand-alone application,
		run the following command:
		</p>
		<p><code>${dollar}JAVA_HOME/bin/java -cp /path/to/log4j-api-${Log4jReleaseVersion}.jar:/path/to/log4j-core-${Log4jReleaseVersion}.jar:/path/to/log4j-jmx-gui-${Log4jReleaseVersion}.jar org.apache.logging.log4j.jmx.gui.ClientGui &lt;options&gt;</code></p>
		<p>or on Windows:</p>
		<p><code>%JAVA_HOME%\bin\java -cp \path\to\log4j-api-${Log4jReleaseVersion}.jar;\path\to\log4j-core-${Log4jReleaseVersion}.jar;\path\to\log4j-jmx-gui-${Log4jReleaseVersion}.jar org.apache.logging.log4j.jmx.gui.ClientGui &lt;options&gt;</code></p>
		<p>Where <code>options</code> are one of the following:</p>
		<ul>
		<li><code>&lt;host&gt;:&lt;port&gt;</code></li>
		<li><code>service:jmx:rmi:///jndi/rmi://&lt;host&gt;:&lt;port&gt;/jmxrmi</code></li>
		<li><code>service:jmx:rmi://&lt;host&gt;:&lt;port&gt;/jndi/rmi://&lt;host&gt;:&lt;port&gt;/jmxrmi</code></li>
		</ul>
		<p>The port number must be the same as the portNum specified when
		you started the application you want to monitor.
		</p>
		<p>For example, if you started your application with these options:</p>
		<pre>com.sun.management.jmxremote.port=33445
com.sun.management.jmxremote.authenticate=false
com.sun.management.jmxremote.ssl=false</pre>
		<p><b>(Note that this disables <em>all</em> security so this is not recommended
		for production environments.
		Oracle's documentation on
        <a href="https://docs.oracle.com/javase/7/docs/technotes/guides/management/agent.html#gdenl">Remote
        Monitoring and Management</a> provides details on how to configure
        JMX more securely with password authentication and SSL.)</b></p>
		<p>Then you can run the client with this command:</p>
		<p><code>${dollar}JAVA_HOME/bin/java -cp /path/to/log4j-api-${Log4jReleaseVersion}.jar:/path/to/log4j-core-${Log4jReleaseVersion}.jar:/path/to/log4j-jmx-gui-${Log4jReleaseVersion}.jar org.apache.logging.log4j.jmx.gui.ClientGui localhost:33445</code></p>
		<p>or on Windows:</p>
		<p><code>%JAVA_HOME%\bin\java -cp \path\to\log4j-api-${Log4jReleaseVersion}.jar;\path\to\log4j-core-${Log4jReleaseVersion}.jar;\path\to\log4j-jmx-gui-${Log4jReleaseVersion}.jar org.apache.logging.log4j.jmx.gui.ClientGui localhost:33445</code></p>
		<p>The screenshot below shows the StatusLogger panel of the client
		GUI when running as a stand-alone application.</p>
        <p><img src="../images/jmx-standalone-statuslogger.png" alt="JMX GUI screenshot of StatusLogger display" /></p>
		<p>The screenshot below shows the configuration editor panel of the
		client GUI when running as a stand-alone application.</p>
        <p><img src="../images/jmx-standalone-editconfig.png" alt="JMX GUI screenshot of configuration editor" /></p>

		</subsection>
      </section>

    </body>
</document>
