How to log multiple threads in different log files?

Question

I have a JAVA class that starts various threads that have unique IDs. Each thread should log into a unique log file, named after the ID.log.

Because I only get the u

Answer 1

For log4j v2 you can use RoutingAppender to dynamically route messages. You can put value for key 'threadId' into the ThreadContext map and then use this id as a part of the file name. There is an example which I have easily applied for the same purpose as yours. See http://logging.apache.org/log4j/2.x/faq.html#separate_log_files

Be aware when putting values into ThreadContext map: "A child thread automatically inherits a copy of the mapped diagnostic context of its parent." So if you have put a value for key 'threadId' into the parent thread and eventually created multiple threads from it, then all child threads will inherit the value of 'threadId' value. I was not able to simply override this value by using put() one more time - you need to use ThreadContext.clear() or explicitly remove() the value from thread context map.

Here is my working log4j.xml:

    
        %d{HH:mm:ss} %-5level - %msg%n
        test logs