TasksQueue doesn't remove entry from tasks on RejectedExecutionException

[ahus1]

Version

master branch.

Context

I had a look at the code when analyzing a problem in the 4.4.x after I configured a thread pool with a limited backlog which would reject executions eventually.

I found that the code in master throws the exception that the task is rejected, but then the task is still in the taskQueue, so it will eventually be executed when another task is then successfully submitted.
So for the caller it is both rejected and accepted, which is confusing and IMHO wrong.

I'll create a different issue for that as it doesn't handle the RejectedExecutionException at all.

Do you have a reproducer?

Here a unit test as a reproducer - not that (at least for the reproducer) I made the tasks attribute public to I can use it the test. See https://github.com/ahus1/vert.x/tree/poc-show-how-taskqueue-fails-in-main

    TaskQueue taskQueue = new TaskQueue();
    Executor executorThatAlwaysThrowsRejectedExceptions = new Executor() {
        @Override
        public void execute(Runnable command) {
            throw new RejectedExecutionException();
        }
    };

    assertThatThrownBy(() -> {
        taskQueue.execute(new Thread(), executorThatAlwaysThrowsRejectedExceptions);
      }).isInstanceOf(RejectedExecutionException.class);

    // this fails in main
    Assertions.assertThat(taskQueue.tasks).isEmpty();

Steps to reproduce

See test.

Extra

I can start writing a test, but I'm not sure on how to test this.

[ahus1]

I've created PR #4901. Once this change has been discussed and agreed, I'd be happy to provide a backport to 4.4.x, as I plan to use it in the Keycloak project, which uses this dependency via the Quarkus project.

[ahus1]

Prepared a backport #4904 for the 4.x branch.