LoggingGCRaceConditionTester.java

import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


public class LoggingGCRaceConditionTester {

   private static final Logger _log = LoggerFactory.getLogger(LoggingGCRaceConditionTester.class);

   /**
    * Start with -Xmx2G
    */
   public static void main( String[] args ) {
      new LoggingGCRaceConditionTester().test();
   }

   private static void joinQuietly( Thread t ) {
      try {
         t.join();
      }
      catch ( InterruptedException e ) {
         throw new RuntimeException(e);
      }
   }

   private static void setDaemon( Thread t ) {t.setDaemon(true);}

   private volatile boolean endlessLoop = true;

   void test() {
      List<Thread> threads = List.of( //
            new Thread(this::log, "Logger loop"), //
            new Thread(this::gc, "GC loop") //
      );
      threads.forEach(LoggingGCRaceConditionTester::setDaemon);
      threads.forEach(Thread::start);
      threads.forEach(LoggingGCRaceConditionTester::joinQuietly);
   }

   private void gc() {
      try {
         Thread.sleep(10); // give the log thread a headstart
      }
      catch ( InterruptedException e ) {
         throw new RuntimeException(e);
      }

      while ( true ) {
         Thread.yield();
         System.gc();
      }
   }

   private void log() {
      long suffix = 0;
      boolean npe = false;

      while ( true ) {
         try {
            String name = "TestLogger" + (++suffix);
            try {
               Logger l = LoggerFactory.getLogger(name);
               if ( npe || (suffix % 100) == 0 ) {
                  l.info("");
               } else {
                  l.trace("");
               }
            }
            catch ( NullPointerException t ) {
               _log.warn("{} threw {}: {}", name, t.getClass().getSimpleName(), t.getMessage());
               npe = true;
            }
            catch ( Throwable t ) {
               _log.error("{} threw {}: {}", name, t.getClass().getSimpleName(), t.getMessage());
            }
         }
         catch ( Throwable t ) {
            _log.error("caught", t);
         }
      }
   }
}