/**
   * Event callback.
   *
   * @param exchId Exchange ID.
   * @param discoEvt Discovery event.
   */
  public void onEvent(GridDhtPartitionExchangeId exchId, DiscoveryEvent discoEvt) {
    assert exchId.equals(this.exchId);

    this.discoEvt = discoEvt;

    evtLatch.countDown();
  }
  /** {@inheritDoc} */
  @Override
  public String toString() {
    ClusterNode oldestNode = this.oldestNode.get();

    return S.toString(
        GridDhtPartitionsExchangeFuture.class,
        this,
        "oldest",
        oldestNode == null ? "null" : oldestNode.id(),
        "oldestOrder",
        oldestNode == null ? "null" : oldestNode.order(),
        "evtLatch",
        evtLatch == null ? "null" : evtLatch.getCount(),
        "remaining",
        remaining(),
        "super",
        super.toString());
  }
  /**
   * JUnit.
   *
   * @throws Exception If failed.
   */
  public void testQueueRemoveMultithreadBounded() throws Exception {
    // Random queue name.
    final String queueName = UUID.randomUUID().toString();

    final IgniteQueue<String> queue = grid(0).queue(queueName, QUEUE_CAPACITY, config(false));

    final CountDownLatch putLatch = new CountDownLatch(THREAD_NUM);

    final CountDownLatch clearLatch = new CountDownLatch(THREAD_NUM);

    for (int t = 0; t < THREAD_NUM; t++) {
      Thread th =
          new Thread(
              new Runnable() {
                @Override
                public void run() {
                  if (log.isDebugEnabled())
                    log.debug("Thread has been started." + Thread.currentThread().getName());

                  try {
                    // Thread must be blocked on put operation.
                    for (int i = 0; i < (QUEUE_CAPACITY * THREAD_NUM); i++)
                      queue.offer("anything", 3, TimeUnit.MINUTES);

                    fail("Queue failed");
                  } catch (IgniteException | IllegalStateException e) {
                    putLatch.countDown();

                    assert e.getMessage().contains("removed");

                    assert queue.removed();
                  }

                  if (log.isDebugEnabled())
                    log.debug("Thread has been stopped." + Thread.currentThread().getName());
                }
              });
      th.start();
    }

    for (int t = 0; t < THREAD_NUM; t++) {
      Thread th =
          new Thread(
              new Runnable() {
                @Override
                public void run() {
                  try {
                    IgniteQueue<String> queue = grid(0).queue(queueName, 0, null);

                    if (queue != null) queue.close();
                  } catch (Exception e) {
                    fail("Unexpected exception: " + e);
                  } finally {
                    clearLatch.countDown();
                  }
                }
              });
      th.start();
    }

    assert putLatch.await(3, TimeUnit.MINUTES);

    assert clearLatch.await(3, TimeUnit.MINUTES);

    try {
      assert queue.isEmpty() : queue.size();

      fail("Queue must be removed.");
    } catch (IgniteException | IllegalStateException e) {
      assert e.getMessage().contains("removed");

      assert queue.removed();
    }
  }