protected long crawlingExecutionInterval = Constants.DEFAULT_CRAWLING_EXECUTION_INTERVAL;

    /**
     * Thread priority for index updater operations.
     */
    protected int indexUpdaterPriority = Thread.MAX_PRIORITY;

    /**
     * Thread priority for crawler operations.
     */
    protected int crawlerPriority = Thread.NORM_PRIORITY;

    /**
     * Synchronized list of active crawlers.
     */

 * {@link Map} specified in the {@link Table} interface.
 *
 * <p>Note that this implementation is not synchronized. If multiple threads access this table
 * concurrently and one of the threads modifies the table, it must be synchronized externally.
 *
 * <p>See the Guava User Guide article on <a href=

 * possibly run in another thread. That cause should itself be an {@code Error}; if not, use {@code
 * ExecutionException} or {@link UncheckedExecutionException}. This allows the client code to
 * continue to distinguish between exceptions and errors, even when they come from other threads.
 *
 * @author Chris Povirk
 * @since 10.0
 */
@GwtCompatible

   * {@linkplain Thread#getContextClassLoader() context class loader}. In simple environments, the
   * context class loader will find resources from the class path. In environments where different
   * threads can have different class loaders, for example app servers, the context class loader
   * will typically have been set to an appropriate loader for the current thread.
   *

 * an {@code ArrayTable} concurrently and one of the threads modifies its value, there is no
 * guarantee that the new value will be fully visible to the other threads. To guarantee that
 * modifications are visible, synchronize access to the table. Unlike other {@code Table}
 * implementations, synchronization is unnecessary between a thread that writes to one cell and a

   * calling thread. Tasks are run to completion before a {@code Future} is returned to the caller
   * (unless the executor has been shutdown).
   *
   * <p>The returned executor is backed by the executor returned by {@link
   * MoreExecutors#newDirectExecutorService} and subject to the same constraints.
   *
   * <p>Although all tasks are immediately executed in the thread that submitted the task, this

     * Sets the uncaught exception handler for this IndexUpdater thread.
     *
     * @param eh the uncaught exception handler to set
     */
    @Override
    public void setUncaughtExceptionHandler(final UncaughtExceptionHandler eh) {
        super.setUncaughtExceptionHandler(eh);
    }

    /**
     * Sets the default uncaught exception handler for all threads.
     *

    assertFalse(future.isDone());
    assertFalse(future.isCancelled());

    CountDownLatch successLatch = new CountDownLatch(1);

    // Run cancellation in a separate thread as an extra thread-safety test.
    new Thread(
            () -> {
              assertThrows(CancellationException.class, future::get);
              successLatch.countDown();
            })
        .start();

                .forEach(s -> buf.append(s));
        log(buf);
    }

    /**
     * Increments the thread reference count for the specified crawler object.
     * Used when the same object is being processed on multiple threads.
     *
     * @param keyObj the crawler object running on an additional thread
     */
    public void runOnThread(final Object keyObj) {
        getCacheKey(keyObj).ifPresent(key -> {

 * due to eviction resulting from timed expiration, exceeding a maximum size, or garbage collection.
 *
 * <p>An instance may be called concurrently by multiple threads to process different entries.
 * Implementations of this interface should avoid performing blocking calls or synchronizing on
 * shared resources.
 *