log4j2: Include PID

I'm using log4j2, and running multiple instances of the same code in different processes (ie different JVMs) at the same time. I'd like all processes to log to the same file, interleaved How can I configure (via log4j2.xml) to output the PID, so that the different processes can be distinguished in the logs?

回答1:

Perhaps MDC can help you. Try this:

Java:

import java.lang.management.ManagementFactory;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.ThreadContext;

public class TestPID {

    private static final Logger LOG = LogManager.getLogger(TestPID.class);

    static {
        // Get the process id
        String pid = ManagementFactory.getRuntimeMXBean().getName().replaceAll("@.*", "");

        // MDC
        ThreadContext.put("pid", pid);
    }

    public static void main(String[] args) {
        LOG.info("Testing...");
    }

}

XML:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d %5X{pid} %-5p %c#%M - %m%n" />
    </Console>
  </Appenders>
  <Loggers>
    <Root level="info">
      <AppenderRef ref="Console" />
    </Root>
  </Loggers>
</Configuration>

Output:

2014-09-10 00:13:49,281  7164 INFO  TestPID#main - Testing...
                         ↑↑↑↑
                    That's the PID

You may want to see:

Layouts - PatternLayout
Effective Logging in Java/JEE – Mapped Diagnostic Context
How can a Java program get its own process ID?
How to use MDC with thread pools?

回答2:

There is a plugin ProcessIdPatternConverter in log4j2-core since version 2.9 that does exactly this.

just setting %pid or %processId in the pattern layout logs it.

log4j documentation: https://logging.apache.org/log4j/2.x/manual/layouts.html