Question

If I have a log4j logger in a class that implements Runnable:

MyTask implements Runnable {
  private static final Logger log = Logger.getLogger(MyTask.class);
  ...
}

If I create many instances of this Runnable and submit them to an ExecutorService on a multi-core machine where they run in parallel, and they all write to the static Logger, this seems like there is a risk of contention. A better pattern seems to be:

MyTask implements Runnable {
  private final Logger log;
  MyTask(String name) {
    log = Logger.getLogger(name);
  }
  ...
}   

So my question… is this a pattern you have used or found necessary as at the moment I am purely hypothesising?

Thanks

Answer 1

It is very typical to share a static class logger among many threads. Typically the logger has an underlying PrintStream which is already synchronized, so creating more than one Logger is unnecessary and wasteful.