qwwqwwq qwwqwwq - 1 year ago 752
Java Question

Process Id in Logback Logging Pattern

I have the following logback pattern:

{"hostname": "${HOSTNAME}",
"level": "%p",
"method": "%M",
"process_id": "${process}",
"thread_id": "%t",
"timestamp": "%d{Y-M-d}T%d{H:M:S.s}",

Unfortunately when the log messages are actually generated I see:
"process_id": "process_IS_UNDEFINED"

Is there any automatically set variable for process id, such as there is for hostname? I am having a lot of trouble finding a documented list of such automatically set variables in the logback documentation, does anyone know of a better documentation source?

Edit: I am aware of Mapped Diagnostic Contexts, but was hoping for a builtin solution that does not need such setup, much like how hostname works.

Answer Source

You can solve your problem with Mapped Diagnostic Context:

import org.slf4j.MDC;

public class Main {
    public static void main(String... args) {
        // put process ID early

After that all you need is to re-define your pattern as follows:

<pattern>{..., "process_id": "%X{process_id}"}</pattern>


Also you can create your own encoder and converter and use them in logback.xml:

import ch.qos.logback.classic.PatternLayout;
import ch.qos.logback.classic.encoder.PatternLayoutEncoder;

public class ExtendedPatternLayoutEncoder extends PatternLayoutEncoder {
    public void start() {
        // put your converter
            "process_id", ProcessIdConverter.class.getName());
import ch.qos.logback.classic.pattern.ClassicConverter;
import ch.qos.logback.classic.spi.ILoggingEvent;

import java.lang.management.ManagementFactory;

public class ProcessIdConverter extends ClassicConverter {
    private static final String PROCESS_ID =

    public String convert(final ILoggingEvent event) {
        // for every logging event return processId from mx bean
        // (or better alternative)
        return PROCESS_ID;
<encoder class="some.package.ExtendedPatternLayoutEncoder">
    <pattern>{..., "process_id": "%process_id"}</pattern>
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