/** @param log Logger. */
    private void execute(GridLogger log) {
      try {
        log.info("Started execute.");

        // Countdown shared job latch so that the main thread know that all jobs are
        // inside the "execute" routine.
        jobLatch.countDown();

        log.info("After job latch.");

        // Await for the main thread to allow jobs to proceed.
        latch.await();

        log.info("After latch.");

        if (awaitMasterLeaveCallback) {
          latch0.await();

          log.info("After latch0.");
        } else log.info("Latch 0 skipped.");
      } catch (InterruptedException e) {
        // We do not expect any interruptions here, hence this statement.
        fail("Unexpected exception: " + e);
      }
    }
  /** @throws Exception If failed. */
  @SuppressWarnings("unchecked")
  public void testCancel() throws Exception {
    Grid grid = G.grid(getTestGridName());

    grid.compute()
        .localDeployTask(GridCancelTestTask.class, U.detectClassLoader(GridCancelTestTask.class));

    GridComputeTaskFuture<?> fut = grid.compute().execute(GridCancelTestTask.class.getName(), null);

    // Wait until jobs begin execution.
    boolean await = startSignal.await(WAIT_TIME, TimeUnit.MILLISECONDS);

    assert await : "Jobs did not start.";

    info("Test task result: " + fut);

    assert fut != null;

    // Only first job should successfully complete.
    Object res = fut.get();
    assert (Integer) res == 1;

    // Wait for all jobs to finish.
    await = stopSignal.await(WAIT_TIME, TimeUnit.MILLISECONDS);
    assert await : "Jobs did not stop.";

    // One is definitely processed. But there might be some more processed or cancelled or processed
    // and cancelled.
    // Thus total number should be at least SPLIT_COUNT and at most (SPLIT_COUNT - 1) *2 +1
    assert (cancelCnt + processedCnt) >= SPLIT_COUNT
            && (cancelCnt + processedCnt) <= (SPLIT_COUNT - 1) * 2 + 1
        : "Invalid cancel count value: " + cancelCnt;
  }
  /**
   * @param expJobs Expected jobs number.
   * @param taskStarter Task started.
   * @throws Exception If failed.
   */
  private void testMasterLeaveAwareCallback(
      int expJobs, GridClosure<GridProjection, GridFuture<?>> taskStarter) throws Exception {
    jobLatch = new CountDownLatch(expJobs);
    invokeLatch = new CountDownLatch(expJobs);

    for (int i = 0; i < GRID_CNT; i++) startGrid(i);

    int lastGridIdx = GRID_CNT - 1;

    GridFuture<?> fut = taskStarter.apply(grid(lastGridIdx).forPredicate(excludeLastPredicate()));

    jobLatch.await();

    stopGrid(lastGridIdx, true);

    latch.countDown();

    assert invokeLatch.await(5000, MILLISECONDS);

    try {
      fut.get();
    } catch (GridException e) {
      log.debug("Task failed: " + e);
    }
  }
  /**
   * Ensure that {@link GridComputeJobMasterLeaveAware} callback is invoked when fails to send
   * {@link GridJobExecuteResponse} to master node.
   *
   * @throws Exception If failed.
   */
  public void testCannotSendJobExecuteResponse() throws Exception {
    awaitMasterLeaveCallback = false;

    // Start grids.
    for (int i = 0; i < GRID_CNT; i++) startGrid(i);

    int lastGridIdx = GRID_CNT - 1;

    grid(lastGridIdx)
        .forPredicate(excludeLastPredicate())
        .compute()
        .execute(new TestTask(GRID_CNT - 1), null);

    jobLatch.await();

    for (int i = 0; i < lastGridIdx; i++)
      ((CommunicationSpi) grid(i).configuration().getCommunicationSpi()).waitLatch();

    latch.countDown();

    // Ensure that all worker nodes has already started job response sending.
    for (int i = 0; i < lastGridIdx; i++)
      ((CommunicationSpi) grid(i).configuration().getCommunicationSpi()).awaitResponse();

    // Now we stop master grid.
    stopGrid(lastGridIdx, true);

    // Release communication SPI wait latches. As master node is stopped, job worker will receive
    // and exception.
    for (int i = 0; i < lastGridIdx; i++)
      ((CommunicationSpi) grid(i).configuration().getCommunicationSpi()).releaseWaitLatch();

    assert invokeLatch.await(5000, MILLISECONDS);
  }
  /**
   * Ensure that {@link GridComputeJobMasterLeaveAware} callback is invoked on job which is
   * initiated by master and is currently running on it.
   *
   * @throws Exception If failed.
   */
  public void testLocalJobOnMaster() throws Exception {
    invokeLatch = new CountDownLatch(1);
    jobLatch = new CountDownLatch(1);

    Grid g = startGrid(0);

    g.compute().execute(new TestTask(1), null);

    jobLatch.await();

    // Count down the latch in a separate thread.
    new Thread(
            new Runnable() {
              @Override
              public void run() {
                try {
                  U.sleep(500);
                } catch (GridInterruptedException ignore) {
                  // No-op.
                }

                latch.countDown();
              }
            })
        .start();

    stopGrid(0, true);

    latch.countDown();

    assert invokeLatch.await(5000, MILLISECONDS);
  }
  /** @throws Exception If failed. */
  public void testTopologyListener() throws Exception {
    final Collection<UUID> added = new ArrayList<>(1);
    final Collection<UUID> rmvd = new ArrayList<>(1);

    final CountDownLatch addedLatch = new CountDownLatch(1);
    final CountDownLatch rmvLatch = new CountDownLatch(1);

    assertEquals(NODES_CNT, client.compute().refreshTopology(false, false).size());

    GridClientTopologyListener lsnr =
        new GridClientTopologyListener() {
          @Override
          public void onNodeAdded(GridClientNode node) {
            added.add(node.nodeId());

            addedLatch.countDown();
          }

          @Override
          public void onNodeRemoved(GridClientNode node) {
            rmvd.add(node.nodeId());

            rmvLatch.countDown();
          }
        };

    client.addTopologyListener(lsnr);

    try {
      Grid g = startGrid(NODES_CNT + 1);

      UUID id = g.localNode().id();

      assertTrue(addedLatch.await(2 * TOP_REFRESH_FREQ, MILLISECONDS));

      assertEquals(1, added.size());
      assertEquals(id, F.first(added));

      stopGrid(NODES_CNT + 1);

      assertTrue(rmvLatch.await(2 * TOP_REFRESH_FREQ, MILLISECONDS));

      assertEquals(1, rmvd.size());
      assertEquals(id, F.first(rmvd));
    } finally {
      client.removeTopologyListener(lsnr);

      stopGrid(NODES_CNT + 1);
    }
  }
    /** {@inheritDoc} */
    @Override
    public Serializable execute() {
      int arg = this.<Integer>argument(0);

      try {
        if (log.isInfoEnabled()) log.info("Executing job [job=" + this + ", arg=" + arg + ']');

        startSignal.countDown();

        try {
          if (!startSignal.await(WAIT_TIME, TimeUnit.MILLISECONDS)) fail();

          if (arg == 1) {
            if (log.isInfoEnabled()) log.info("Job one is proceeding.");
          } else Thread.sleep(WAIT_TIME);
        } catch (InterruptedException e) {
          if (log.isInfoEnabled())
            log.info("Job got cancelled [arg=" + arg + ", ses=" + ses + ", e=" + e + ']');

          return 0;
        }

        if (log.isInfoEnabled()) log.info("Completing job: " + ses);

        return argument(0);
      } finally {
        stopSignal.countDown();

        processedCnt++;
      }
    }
  /**
   * Ensure that {@link GridComputeJobMasterLeaveAware} callback is invoked when master node leaves
   * topology normally.
   *
   * @throws Exception If failed.
   */
  public void testMasterStoppedNormally() throws Exception {
    // Start grids.
    for (int i = 0; i < GRID_CNT; i++) startGrid(i);

    int lastGridIdx = GRID_CNT - 1;

    grid(lastGridIdx)
        .forPredicate(excludeLastPredicate())
        .compute()
        .execute(new TestTask(GRID_CNT - 1), null);

    jobLatch.await();

    stopGrid(lastGridIdx, true);

    latch.countDown();

    assert invokeLatch.await(5000, MILLISECONDS);
  }
  /**
   * Ensure that {@link GridComputeJobMasterLeaveAware} callback is invoked when master node leaves
   * topology abruptly (e.g. due to a network failure or immediate node shutdown).
   *
   * @throws Exception If failed.
   */
  public void testMasterStoppedAbruptly() throws Exception {
    // Start grids.
    for (int i = 0; i < GRID_CNT; i++) startGrid(i);

    int lastGridIdx = GRID_CNT - 1;

    grid(lastGridIdx)
        .forPredicate(excludeLastPredicate())
        .compute()
        .execute(new TestTask(GRID_CNT - 1), null);

    jobLatch.await();

    ((CommunicationSpi) grid(lastGridIdx).configuration().getCommunicationSpi()).blockMessages();

    stopGrid(lastGridIdx, true);

    latch.countDown();

    assert invokeLatch.await(5000, MILLISECONDS);
  }