Log4j2: Logger is configured but not usable

Question

I'm working on a JEE REST API and am converting to log4j2. Some of my logging is working, but not others.

I created an appender, monitorAppender. Here's its configuration:

<RollingFile name="monitorAppender" append="true" fileName="${baseDir}/ZDA_monitor.log" filePattern="${baseDir}/ZDA_monitor.log.%i">
    <PatternLayout pattern="%d{yyMMddHHmmssSSS}|%m%x%n"/>
    <Policies>
        <SizeBasedTriggeringPolicy size="10 MB"/>
    </Policies>
    <DefaultRolloverStrategy max="5"/>
</RollingFile>

And logger configuration:

<Logger name="ZDAMonitor" level="info" additivity="false">
    <AppenderRef ref="monitorAppender"/>
</Logger>

In my code when I try to use the logger:

LogManager.getLogger("ZDAMonitor").fatal("Test123");

I see this in the console, instead of the file:

SystemOut O 14:56:50.922 [WebContainer: 1] FATAL ZDAMonitor - Test123

I can't tell what's wrong with the config. I turned on debug logging for log4j and see in the startup logs it's being correctly loaded:

SystemOut O 2023-01-25 14:56:43,490 WebContainer: 1 DEBUG Registering MBean org.apache.logging.log4j2:type=5745d2fa,component=Loggers,name=ZDAMonitor

I can't post the source as this is a company project, but I'm using gradle, log4j-core and api 2.19.0, and WebSphere 8.5.5.22 with Java 1.8.

I've checked and double checked the configuration and code, and cannot find anything wrong with it.

Answer 1

WebSphere has a very peculiar thread context classloader.

The log4j-web module configures a logger context associated to the context classloader. However the context classloader in WebSphere is not the classloader that loaded the classes in your application, so your application's loggers use a different logger context (and a different config). See LOG4J2-3577 for details.

A simple solution would be to use a BasicContextSelector .