private static final LazyLogger logger = new LazyLogger(ListenerCallQueue.class);

  // TODO(chrisn): promote AppendOnlyCollection for use here.
  private final List<PerListenerQueue<L>> listeners =
      Collections.synchronizedList(new ArrayList<PerListenerQueue<L>>());

  /** Method reference-compatible listener event. */
  interface Event<L> {
    /** Call a method on the listener. */
    void call(L listener);
  }

  /**

     */
    protected int crawlerPriority = Thread.NORM_PRIORITY;

    /**
     * Synchronized list of active crawlers.
     */
    protected final List<Crawler> crawlerList = Collections.synchronizedList(new ArrayList<>());

    /**
     * Initiates crawling for specified web and file configurations.
     *
     * @param sessionId The session ID for this crawling operation

    }

    // Test concurrent crawling
    public void test_doCrawl_concurrentWebAndData() {
        final List<String> executionOrder = Collections.synchronizedList(new ArrayList<>());

        WebFsIndexHelper mockWebHelper = new WebFsIndexHelper() {
            @Override
            public void crawl(String sessionId, List<String> webConfigIdList, List<String> fileConfigIdList) {

    /**
     * Thread-safe list of active data crawling threads.
     * Used to track and manage all currently running crawler threads.
     */
    protected final List<DataCrawlingThread> dataCrawlingThreadList = Collections.synchronizedList(new ArrayList<>());

    /**
     * Creates a new instance of DataIndexHelper.
     * This constructor initializes the helper for managing data crawling operations,

      )
    }
    val request =
      Request
        .Builder()
        .url(webServer.url("/"))
        .build()
    val attempts = CountDownLatch(20)
    val webSockets = Collections.synchronizedList(ArrayList<WebSocket>())
    val reconnectOnFailure: WebSocketListener =
      object : WebSocketListener() {
        override fun onFailure(
          webSocket: WebSocket,
          t: Throwable,