*/
    @PreDestroy
    public void destroy() {
        if (!finishCrawling) {
            if (logger.isInfoEnabled()) {
                logger.info("Stopping all crawler.");
            }
            forceStop();
        }
    }

    /**
     * Adds a finished session ID to the cleanup list.

        throw new UnsupportedOperationException("already specified useForNull");
      }
    };
  }

  /**
   * Returns a joiner with the same behavior as this joiner, except automatically skipping over any
   * provided null elements.
   */
  public Joiner skipNulls() {
    return new Joiner(this) {
      @Override
      @SuppressWarnings("JoinIterableIterator") // suggests infinite recursion

 *       once. This reduces the expense of habitually making defensive copies at API boundaries.
 *       However, the precise conditions for skipping the copy operation are undefined.
 *   <li><b>Warning:</b> a view collection such as {@link ImmutableMap#keySet} or {@link
 *       ImmutableList#subList} may retain a reference to the entire data set, preventing it from

   * {@inheritDoc}
   *
   * <p>The returned set has an iterator that does not support {@code remove()}.
   *
   * <p>The set's iterator traverses the columns of the first row, the columns of the second row,
   * etc., skipping any columns that have appeared previously.
   */
  @Override
  public Set<C> columnKeySet() {
    Set<C> result = columnKeySet;
    return (result == null) ? columnKeySet = new ColumnKeySet() : result;
  }

   * obtained by calling {@code snapshot()} on the same {@link StatsAccumulator} without adding any
   * values in between the two calls, or if one is obtained from the other after round-tripping
   * through java serialization. However, floating point rounding errors mean that it may be false
   * for some instances where the statistics are mathematically equal, including instances

//              creating a function with no body (e.g. identity or permutation)
//              and the case of creating a function whose body contains all
//              the nodes in the graph (except for the automatic skipping, see
//              below).
//  opers - Array of operations to become the body of the function or null.
//          - If no array is given (`num_opers` = -1), all the

	// If etcd backend is specified and etcd server is not present, the test
	// is skipped.
	etcdServer := env.Get(EnvTestEtcdBackend, "")
	if s.withEtcdBackend && etcdServer == "" {
		c.Skip("Skipping etcd backend IAM test as no etcd server is configured.")
	}

	s.TestSuiteCommon.SetUpSuite(c)

	s.iamSetup(c)

	if s.withEtcdBackend {
		s.setUpEtcd(c, etcdServer)
	}
}

      runningTask.cancel(false);
      executorService.execute(
          () -> {
            try {
              lock.lock();
              try {
                if (state() != State.STOPPING) {
                  // This means that the state has changed since we were scheduled. This implies
                  // that an execution of runOneIteration has thrown an exception and we have

                    if (encoded.length() > fessConfig.getCookieSearchParameterMaxLengthAsInteger()) {
                        logger.warn("Encoded search parameters exceed the maximum cookie length: {} > {}. Skipping cookie storage.",
                                encoded.length(), fessConfig.getCookieSearchParameterMaxLengthAsInteger());
                        return;
                    }

      runningTask.cancel(false);
      executorService.execute(
          () -> {
            try {
              lock.lock();
              try {
                if (state() != State.STOPPING) {
                  // This means that the state has changed since we were scheduled. This implies
                  // that an execution of runOneIteration has thrown an exception and we have