// Execute concurrently
crawler1.setBackground(true);
crawler2.setBackground(true);

String sessionId1 = crawler1.execute();
String sessionId2 = crawler2.execute();

crawler1.awaitTermination();
crawler2.awaitTermination();
```

### Custom Interval Control

```java
// Configure politeness policy
container.singleton("intervalController", DefaultIntervalController.class, controller -> {

      }
    } finally {
      if (interrupted) {
        Thread.currentThread().interrupt();
      }
    }
  }

  /**
   * Invokes {@code executor.}{@link ExecutorService#awaitTermination(long, TimeUnit)
   * awaitTermination(long, TimeUnit)} uninterruptibly with no timeout.
   *
   * @since 30.0
   */
  @J2ktIncompatible
  @GwtIncompatible // concurrency

                }
                Thread.sleep(50);
            }
            assertEquals(CrawlerStatus.RUNNING, crawler2.crawlerContext.getStatus());

            crawler1.awaitTermination();
            crawler2.awaitTermination();

            assertEquals(maxCount, dataService.getCount(sessionId1));
            assertEquals(maxCount, dataService.getCount(sessionId2));

            UrlQueue urlQueue;

  }

  @Override
  public boolean isTerminated() {
    return delegate.isTerminated();
  }

  @Override
  public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
    Preconditions.checkNotNull(unit, "unit must not be null!");
    return delegate.awaitTermination(timeout, unit);
  }

  @Override
  public <T> ListenableFuture<T> submit(Callable<T> task) {

  }

  @Override
  public boolean isTerminated() {
    return delegate.isTerminated();
  }

  @Override
  public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
    Preconditions.checkNotNull(unit, "unit must not be null!");
    return delegate.awaitTermination(timeout, unit);
  }

  @Override
  public <T> ListenableFuture<T> submit(Callable<T> task) {

            assertEquals(CrawlerStatus.RUNNING, crawler1.crawlerContext.getStatus());
            assertEquals(CrawlerStatus.RUNNING, crawler2.crawlerContext.getStatus());

            crawler1.awaitTermination();
            crawler2.awaitTermination();

            assertEquals(maxCount, dataService.getCount(sessionId1));
            assertEquals(maxCount, dataService.getCount(sessionId2));

            UrlQueue urlQueue;

    assertThat(future2.isDone()).isFalse();

    // Stop the first task. The second task should then run.
    blockingCallable.stop();
    executor.shutdown();
    assertThat(executor.awaitTermination(10, SECONDS)).isTrue();
    assertThat(getDone(future2)).isFalse();
  }

  public void testSecondTaskWaitsForFirstEvenIfCancelled() throws Exception {
    BlockingCallable blockingCallable = new BlockingCallable();

                if (!dataCrawlingThreadList.get(i).isRunning() && Constants.RUNNING.equals(dataCrawlingThreadStatusList.get(i))) {
                    dataCrawlingThreadList.get(i).awaitTermination();
                    dataCrawlingThreadStatusList.set(i, Constants.DONE);
                    activeCrawlerNum--;
                }
            }
            ThreadUtil.sleep(crawlingExecutionInterval);

            assertEquals(CrawlerStatus.RUNNING, crawler1.crawlerContext.getStatus());
            assertEquals(CrawlerStatus.RUNNING, crawler2.crawlerContext.getStatus());

            crawler1.awaitTermination();
            crawler2.awaitTermination();

            assertEquals(maxCount, dataService.getCount(sessionId1));
            assertEquals(maxCount, dataService.getCount(sessionId2));

            UrlQueue urlQueue;

        }
    }

    /**
     * Shutdown the directory lease manager
     */
    public void shutdown() {
        scheduler.shutdown();
        try {
            if (!scheduler.awaitTermination(5, TimeUnit.SECONDS)) {
                scheduler.shutdownNow();
            }
        } catch (InterruptedException e) {
            scheduler.shutdownNow();
            Thread.currentThread().interrupt();