How to add the Process id to a LOG4J log file?

Question

I currently have the below pattern layout in log4j. I want to add the Process id to the log file. How can I do it?

log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%d [%t] %-5p %c - %m%n

Pasted sample log message

2011-01-07 11:48:21,940 [main] INFO  Testing1
2011-01-07 11:48:21,942 [main] INFO  Test.common.ApplicationProperties - Used log4j 

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log4j.properties

"log4j.properties" [Read only] 26 lines, 884 characters
log4j.rootCategory=DEBUG, stdout, A1

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Threshold=WARN
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{yyyy/MM/dd HH:mm:ss}  %-5p  (%c) %m%n


log4j.appender.A1=org.apache.log4j.RollingFileAppender
log4j.appender.A1.Threshold=DEBUG
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%d [%t] %-5p %c - %m%n
log4j.appender.A1.File=/homw/cus/logs/ccl.02.log
log4j.appender.A1.MaxFileSize=5MB
log4j.appender.A1.MaxBackupIndex=40


log4j.category.test.common.DBConnectionPool=WARN
log4j.category.test.common.DataBaseHandler=WARN
log4j.category.test.cttg.tables=WARN
log4j.category.test.middleware.tables=WARN

log4j.logger.org.apache.axis=ERROR
log4j.logger.org.apache.catalina=ERROR

Answer 1

You should use MDC to do it

In the config file :

log4j.appender.stdout.layout.ConversionPattern=%d{yyyy/MM/dd HH:mm:ss}  %-5p  (%c) %m%n %X{PID}

%X{PID} is used to match the context value PID

And then, in the code, before the logging begins :

log4j 1.x

RuntimeMXBean rt = ManagementFactory.getRuntimeMXBean();
String pid = rt.getName();
MDC.put("PID", pid);

log4j 2.x

RuntimeMXBean rt = ManagementFactory.getRuntimeMXBean();
String pid = rt.getName();
ThreadContext.put("PID", pid);

Answer 2

There is no way of doing it using standard Java classes. Generally process ID is appended at file level not at the log level. And here (archived here) is an example of doing it.