*/
    protected String charsetName = CoreLibConstants.UTF_8;

    /**
     * The queue of ciphers for encryption.
     */
    protected Queue<Cipher> encryptoQueue = new ConcurrentLinkedQueue<>();

    /**
     * The queue of ciphers for decryption.
     */
    protected Queue<Cipher> decryptoQueue = new ConcurrentLinkedQueue<>();

    /**
     * Encrypts the given data.
     *

 *   <li>Before processing a URL ({@link #delayBeforeProcessing()})</li>
 *   <li>After processing a URL ({@link #delayAfterProcessing()})</li>
 *   <li>When there are no URLs in the queue ({@link #delayAtNoUrlInQueue()})</li>
 *   <li>While waiting for new URLs to be added to the queue ({@link #delayForWaitingNewUrl()})</li>
 * </ul>
 *
 * <p>
 * Subclasses are responsible for implementing the abstract methods to define the actual delay

        for (UrlQueueImpl<Long> queue : queueList) {
            assertEquals(sessionId, queue.getSessionId());
            assertEquals(Integer.valueOf(0), queue.getDepth());
            assertNotNull(queue.getCreateTime());

            if ("https://example.com/page1".equals(queue.getUrl())) {
                foundPage1 = true;
                assertEquals("GET", queue.getMethod());

            // Default constructor
        }

        /**
         * The queue for URLs waiting to be crawled.
         */
        protected Queue<OpenSearchUrlQueue> waitingQueue = new ConcurrentLinkedQueue<>();

        /**
         * The queue for URLs currently being crawled.
         */
        protected Queue<OpenSearchUrlQueue> crawlingQueue = new ConcurrentLinkedQueue<>();
    }

    /**

    private static final int MAX_BUFFER_SIZE = 0x100000; // 1MB maximum

    // Use concurrent queue for lock-free operations
    private static final java.util.concurrent.ConcurrentLinkedQueue<byte[]> bufferQueue =
            new java.util.concurrent.ConcurrentLinkedQueue<>();

    // Track queue size with atomic counter for efficiency

    /** The metadata associated with the URL queue. */
    protected String metaData;

    /** The encoding of the URL queue. */
    protected String encoding;

    /** The parent URL of the current URL in the queue. */
    protected String parentUrl;

    /** The depth of the URL in the queue. */
    protected Integer depth;

    /** The last modified timestamp of the URL in the queue. */
    protected Long lastModified;

    }

    /**
     * Adds a URL to the crawling queue.
     * @param url The URL to add.
     */
    public void addUrl(final String url) {
        try {
            urlQueueService.add(crawlerContext.sessionId, url);
            if (logger.isDebugEnabled()) {
                logger.debug("Added URL to queue: url={}, sessionId={}", url, crawlerContext.sessionId);
            }

        assertTrue(fesenClient.prepareSearch("fess_crawler.queue")
                .setQuery(QueryBuilders.termQuery("sessionId", "id1"))
                .execute()
                .actionGet()
                .getHits()
                .getTotalHits()
                .value() > 0);
        assertTrue(fesenClient.prepareSearch("fess_crawler.queue")
                .setQuery(QueryBuilders.termQuery("sessionId", "id2"))

    }

    private RESPONSE response = null;

    private Throwable error = null;

    private final Promise promise = new Promise();

    private final Queue<Consumer<RESPONSE>> doneCallbacks = new LinkedBlockingQueue<>();

    private final Queue<Consumer<Throwable>> errorCallbacks = new LinkedBlockingQueue<>();

    private final CountDownLatch latch = new CountDownLatch(1);

    /**

    /**
     * Maximum size of the thumbnail generation task queue.
     */
    protected int thumbnailTaskQueueSize = 10000;

    /**
     * Number of tasks to process in bulk operations.
     */
    protected int thumbnailTaskBulkSize = 100;

    /**
     * Timeout in milliseconds for thumbnail task queue operations.
     */
    protected long thumbnailTaskQueueTimeout = 10 * 1000L;