log4j2.disableJmx and/or log4j2.disable.jmx seem not to work

[autumoswitzerland]

Description

System property switches "log4j2.disableJmx" and/or "log4j2.disable.jmx" seem not to work!

Configuration

Version: 2.23.1 with slf4j 1.7.36

Operating system: Linux Mint 21.2 Cinnamon

JDK: Azu Zulu Build of OpenJDK - Zulu17.52+17-CA 17.0.12+7-LTS, Java version 17.0.12

Logs

2024-07-27T21:19:27.967946158Z main ERROR Could not reconfigure JMX java.lang.NoClassDefFoundError: javax/management/InstanceNotFoundException
	at org.apache.logging.log4j.core.LoggerContext.setConfiguration(LoggerContext.java:642)
	at org.apache.logging.log4j.core.LoggerContext.reconfigure(LoggerContext.java:713)
	at org.apache.logging.log4j.core.LoggerContext.reconfigure(LoggerContext.java:735)
	at org.apache.logging.log4j.core.LoggerContext.start(LoggerContext.java:260)
	at org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextFactory.java:154)
	at org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextFactory.java:46)
	at org.apache.logging.log4j.LogManager.getContext(LogManager.java:197)
	at org.apache.logging.log4j.spi.AbstractLoggerAdapter.getContext(AbstractLoggerAdapter.java:136)
	at org.apache.logging.slf4j.Log4jLoggerFactory.getContext(Log4jLoggerFactory.java:58)
	at org.apache.logging.log4j.spi.AbstractLoggerAdapter.getLogger(AbstractLoggerAdapter.java:46)
	at org.apache.logging.slf4j.Log4jLoggerFactory.getLogger(Log4jLoggerFactory.java:32)
	at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:363)
	at ch.autumo.ifacex.studio.IfaceXStudio.<clinit>(IfaceXStudio.java:77)
	at ch.autumo.ifacex.studio.Main.main(Main.java:26)
Caused by: java.lang.ClassNotFoundException: javax.management.InstanceNotFoundException
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown Source)
	at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
	... 14 more

2024-07-27T21:19:28.390794174Z main ERROR Could not reconfigure JMX java.lang.NoClassDefFoundError: javax/management/InstanceNotFoundException
	at org.apache.logging.log4j.core.LoggerContext.setConfiguration(LoggerContext.java:642)
	at org.apache.logging.log4j.core.LoggerContext.reconfigure(LoggerContext.java:739)
	at org.apache.logging.log4j.core.config.Configurator.reconfigure(Configurator.java:263)
	at ch.autumo.commons.logging.Log4j2Logging.initializeInMemory(Log4j2Logging.java:184)
	at ch.autumo.commons.logging.Log4j2Logging.initializeInMemoryFile(Log4j2Logging.java:87)
	at ch.autumo.ifacex.studio.IfaceXStudio.main(IfaceXStudio.java:797)
	at ch.autumo.ifacex.studio.Main.main(Main.java:26)
Caused by: java.lang.ClassNotFoundException: javax.management.InstanceNotFoundException
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown Source)
	at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
	... 7 more

Java-Code:

    public static void main(String[] args) {
        System.setProperty("log4j2.disable.jmx", "true");
        System.setProperty("log4j2.disableJmx", "true");
        ...

Later:

org.apache.logging.log4j.core.config.Configurator.reconfigure(builder.build());

Reproduction

It's a linux jpackaged executable. Those JMX bean class-not-found-exceptions are only triggered on linux, the same code on Windows and mac doesn't even seem to miss any JMX code. The log4j2-JMX disable switches seem to have no effect. I wonder if they are even filled into the log4j component properties ?!

[vy]

@autumoswitzerland, thanks for your report, much appreciated. The described behaviour is indeed unexpected. I will create a custom Java runtime and try to reproduce the error – when JMX is disabled, the java.management module (providing InstanceNotFoundException) should not be required.

In the meantime,

1. Could you share the packaged modules (java.base, java.compiler, etc.) in your Windows and Linux Java runtimes?
2. Could you try setting the LOG4J_DISABLE_JMX=true environment variable to cross out the initialization order hiccup?
3. Could you try (explicitly?) adding the java.management module?

[ppkarwasz]

The code seems to work as expected, the only problem I see is the severity of the status logger call, which should not be ERROR but INFO or DEBUG:

logging-log4j2/log4j-core/src/main/java/org/apache/logging/log4j/core/LoggerContext.java

Lines 641 to 646 in f0cb225

	try {
	Server.reregisterMBeansAfterReconfigure();
	} catch (final LinkageError | Exception e) {
	// LOG4J2-716: Android has no java.lang.management
	LOGGER.error("Could not reconfigure JMX", e);
	}

logging-log4j2/log4j-core/src/main/java/org/apache/logging/log4j/core/jmx/Server.java

Lines 133 to 141 in f0cb225

	public static void reregisterMBeansAfterReconfigure() {
	// avoid creating Platform MBean Server if JMX disabled
	if (isJmxDisabled()) {
	LOGGER.debug("JMX disabled for Log4j2. Not registering MBeans.");
	return;
	}
	final MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
	reregisterMBeansAfterReconfigure(mbs);
	}

Unless I am mistaken the Server.reregisterMBeansAfterReconfigure() can throw a linkage error at any moment:

• a very eager JVM could throw the exception when the Server class is initialized (if it resolves all the references in its methods)
• a less eager JVM could throw the exception when the reregisterMBeansAfterReconfigure() method is called,
• only a very lazy JVM will evaluate the if statement on line 135.

To solve this issue I would propose to test the value of log4j2.disableJmx configuration property in the LoggerContext class, before we even reference the Server class.

[vy]

@autumoswitzerland, I have verified that log4j-core still requires the java.management module even when JMX is disabled. I have fixed this issue in #2775, which will be released with the next Log4j version, that is, 2.24.0. Note that JMX is disabled by default in 2.24.0 😉, hence you won't need to explicitly disable it anymore.

As a temporary workaround, you need to add java.management module to your runtime.

[autumoswitzerland]

Thanks for the quick response and checking of the issue! It is not really critical, it was more a surprising behaviour on Linux.
Do you still need any of the artefacts (1-3) you requested above?

Still wondering why the switch is not in the log4j2 component properties, because that is imho the real issue; The system property is not copied into the component properties. Therefore, isJmxDisabled = false, at least on Linux! If it were true as expected, the dependency to java.management would be irrelevant. No?

[autumoswitzerland]

Addendum, request No. 2. See attached image.