Get PID in logback log file

When using logback outside of Spring-Boot, how can I get the ProcessID into the log file name?

In the RollingFileAppender I’d like to define:

<file>my-log-${PID}.log</file>

How can I get the ${PID} set or is there a standard way of obtaining this?

Answer

1. Learn how to get the own PID from inside the JVM – How can a Java program get its own process ID?

   ProcessHandle.current().pid()
   

2. Create a custom PropertyDefiner:

   package com.example;
   import ch.qos.logback.core.PropertyDefinerBase;
   
   class PidPropertyDefiner extends PropertyDefinerBase {
     public String getPropertyValue() {
       return Long.toString(ProcessHandle.current().pid());
     }
   }
   

3. Use that property definer to inject a property into the logback:

    <define name="SELF_PID" class="com.example.PidPropertyDefiner" />
   

… or use the logback.groovy instead of logback.xml, there you can just access every bit of JVM directly.