Igloo logging (log4j2 JMX configuration)#

org.iglooproject.components:log4j2-jmx-helper and org.iglooproject.components:jul-helper allow to override log4j2 configuration at runtime (including not predefined loggers and JUL loggers, contrary to log4j2 native JMX implementation).

Source code is hosted at igloo-project/igloo-logging.

This modules do not rely on igloo framework and can be used independently of igloo.

Prerequisites#

Your projet must manage/include the following dependencies:

javax.servlet:javax.servlet-api: javax package, only servlet listener API is used
jakarta.servlet:jakarta.servlet-api: jakarta package, only servlet listener API is used
org.slf4j:jul-to-slf4j: 1.7.x or 2.0.x
org.slf4j:slf4j-api: 1.7.x or 2.0.x
org.apache.logging.log4j:log4j-core: 2.17+ version

Project uses only mainline API from these dependencies and may adapt to any recent version.

Jakarta or Javax servlet API is used based on the listener classes you use.

Installation#

Ensure you use Igloo maven repository: https://nexus.tools.kobalt.fr/repository/igloo-releases/.

Add org.iglooproject.components:log4j2-jmx-helper and org.iglooproject.components:jul-helper to your project’s dependencies.

Remove org.iglooproject.components:igloo-component-jul-to-slf4j as jul-helper handles sl4j to JUL binding.

		<dependency>
			<groupId>org.iglooproject.components</groupId>
			<artifactId>jul-helper</artifactId>
			<version>1.0.1</version>
			<scope>runtime</scope>
		</dependency>
		<dependency>
			<groupId>org.iglooproject.components</groupId>
			<artifactId>log4j2-jmx-helper</artifactId>
			<version>1.0.1</version>
			<scope>runtime</scope>
		</dependency>

		<!-- check dependency tree for the following dependencies -->
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>jul-to-slf4j</artifactId>
		</dependency>
		<dependency>
			<groupId>org.apache.logging.log4j</groupId>
			<artifactId>log4j-core</artifactId>
		</dependency>

For a war project, use web.xml listeners to trigger JMX helper loading (you must replace org.iglooproject.slf4j.jul.bridge.SLF4JLoggingListener if present):

	<!-- javax API (Tomcat < 10) -->
	<listener>
		<listener-class>igloo.julhelper.servlet.JulLoggingListener</listener-class>
	</listener>
 	<listener>
		<listener-class>igloo.log4j2jmx.servlet.Log4j2LoggingManagerListener</listener-class>
	</listener>

	<!-- jakarta API (Tomcat >= 10) -->
	<listener>
		<listener-class>igloo.julhelper.servlet.JakartaJulLoggingListener</listener-class>
	</listener>
 	<listener>
		<listener-class>igloo.log4j2jmx.servlet.JakartaLog4j2LoggingManagerListener</listener-class>
	</listener>

	// java API
	@Override
	public void onStartup(ServletContext servletContext) throws ServletException {
		// ...
		servletContext.addListener(JulLoggingListener.class);
		servletContext.addListener(Log4j2LoggingManagerListener.class);
	}

	// jakarta API
	@Override
	public void onStartup(ServletContext servletContext) throws ServletException {
		// ...
		servletContext.addListener(JakartaJulLoggingListener.class);
		servletContext.addListener(JakartaLog4j2LoggingManagerListener.class);
	}

Else you need to invoke JulLoggingManagerMBean.registerMBean() and Log4j2LoggingManagerMBean.registerMBean().

Jul helper must be initialized before Log4j2 helper.

Usage#

Your MBeans tree must show a new igloo subtree with two type=LoggingManager MBeans:

JulLoggingManager
Log4j2LoggingManager

JulLoggingManager is controlled by Log4j2LoggingManager. It is not needed to interact directly with it.

Use an MBean browser (visualvm, jmxterm) to override your configurations at runtime. Any modification performed is lost at application restart.

Here are examples for jmxterm:

# MBean selection
bean igloo:type=LoggingManager,name=Log4j2LoggingManager
# MBean operations/attributes
info
# Override a logger
run setLevel "org.apache.wicket" "debug"
# Loading a web page may trigger debug logs
run reset
# Logger level must be restore to its previous state

JUL implementation#

Specific code is needed to allow JUL reconfiguration at runtime, because jul-to-slf4j performs log redirection at root level (default behavior in SLF4JBridgeHandler.install()).

It implies to configure JUL not to block any log record, so that they can fo to root logger, so that SLF4JBridgeHandler can redirect it to log4j2. It implies a performance hit as not wanted log record need to be processed.

A common caveat is that JUL must be configured for maximum verbosity. Else high verbosity log records are discarded before jul-to-slf4j can redirect it.

JUL helper allow to automatically add and remove SLF4JBridgeHandler for the provided logger name when log4j2 is reconfigured to address this issues.

jullKnownLoggers setting (can be configured at runtime with JMX, or at startup-time with JulLoggingListener julKnownLoggersResourcePath servlet parameter) is used to limit SLF4JBridgeHandler initialization.

Default configuration is located in jul-helper/well-known-jul-loggers.txt classpath resource. By default, SLF4JBridgeHandler initialization is performed only for logger (and sub loggers):

org.glassfish.jersey
com.google.common

Project release#

Use jgitflow procedure.

Changelog#

1.1.0 (28.08.2023)#

Support both javax.servlet and jakarta.servlet API. You must use appropriate listener variant for you application:

unchanged for javax: JulLoggingListener and Log4j2LoggingManagerListener
jakarta: JakartaJulLoggingListener and JakartaLog4j2LoggingManagerListener

1.0.2 (13.02.2023)#

Fix error messages when servlet is stopped due to servlet listener not registering installed mbeanObjectName at startup

1.0.1 (10.02.2023)#

Fix a deployment issue

1.0.0 (10.02.2023)#

Initial release
Use 1.0.1 that fixes a deployment issue

Igloo logging (log4j2 JMX configuration)

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