RejectedExecutionException coming from single thread executor

Question

Below is my method in which I have single thread executor to execute some task in the run method.

  private void trigger(final Packet packet) {

    // this line is throwing exception
    Executors.newSingleThreadExecutor().execute(new Runnable() {
      @Override
      public void run() {
        // some code here
      }
    });
  }

Below is the exception I am getting and I am not sure why? What is the best way to fix this?

error= java.util.concurrent.RejectedExecutionException: Task com.abc.stuffProc$2@e033da0 rejected from java.util.concurrent.ThreadPoolExecutor@76c2da8f[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 0]
    at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2048)
    at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:821)
    at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1372)
    at java.util.concurrent.Executors$DelegatedExecutorService.execute(Executors.java:628)

What happens if my trigger method is called many times and it is still working on the run method from my previous threads? Will it launch as many threads or it will wait for one thread to finish and then start another thread?

Answer 1

See here: What could be the cause of RejectedExecutionException

as you could see from the error log, your ThreadPoolExecutor is Terminated.

Maybe this is what you want:

private void trigger(final Packet packet) {

    executor.execute(new Runnable() {
      @Override
      public void run() {
        // some code here
      }
    });
  }

private final ExecutorService executor = Executors.newFixedThreadPool(10);

EDIT Reproduce the Problem with:

public static void main(String[] args) {
    final ExecutorTest et = new ExecutorTest();
    for (int i = 0; i < 50000; i++) {
        et.trigger(i);
    }
    System.out.println("Done");
}

private void trigger(int i) {

    try {
        Executors.newSingleThreadExecutor().execute(() -> {
            try {
                Thread.sleep(1000);
            } catch (final InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        });
    } catch (final Exception e) {
        System.out.println("Test " + i + " with " + Thread.activeCount());
        e.printStackTrace();
    }
}