}

    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);

    /**

	"http://dbflute.org/meta/lastadi10.dtd">
<components namespace="fessCrawler">
	<component name="crawlerConfig" class="org.codelibs.fess.crawler.util.FessCrawlerConfig">
		<property name="queueIndex">"fess_crawler.queue"</property>
		<property name="queueShards">5</property>
		<property name="queueReplicas">1</property>
		<property name="dataIndex">"fess_crawler.data"</property>
		<property name="dataShards">5</property>

  private void weaklyReferenceQueue() {
    frq = new FinalizableReferenceQueue();
    queueReference = new WeakReference<>(frq.queue);

    /*
     * Queue and clear a reference for good measure. We test later on that
     * the finalizer thread stopped, but we should test that it actually
     * started first.
     */
    reference =

  private void weaklyReferenceQueue() {
    frq = new FinalizableReferenceQueue();
    queueReference = new WeakReference<>(frq.queue);

    /*
     * Queue and clear a reference for good measure. We test later on that
     * the finalizer thread stopped, but we should test that it actually
     * started first.
     */
    reference =

      return created;
    }

    // N.B. Draining the queue is only necessary to ensure that we don't accumulate empty references
    // in the array. We could skip this if we decide we don't care about holding on to Reference
    // objects indefinitely.
    private void drainQueue() {
      Reference<? extends L> ref;
      while ((ref = queue.poll()) != null) {

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.IOException;
import java.io.Reader;
import java.nio.CharBuffer;
import java.util.ArrayDeque;
import java.util.Queue;
import org.jspecify.annotations.Nullable;

/**
 * A class for reading lines of text. Provides the same functionality as {@link
 * java.io.BufferedReader#readLine()} but for all {@link Readable} objects, not just instances of

import org.codelibs.fess.crawler.service.UrlQueueService;

import jakarta.annotation.Resource;

/**
 * The Crawler class is the main class for web crawling. It manages the crawling process,
 * including adding URLs to the queue, filtering URLs, managing crawler threads,
 * and handling the overall crawling lifecycle.
 *
 * <p>It implements the Runnable interface to be executed in a separate thread,

   * {@link MoreExecutors#directExecutor}. Normally, when the first future completes, all the other
   * tasks would be called recursively. Here, we detect that the delegate executor is executing
   * inline, and maintain a queue to dispatch tasks iteratively. There is one instance of this class
   * per call to submit() or submitAsync(), and each instance supports only one call to execute().
   *

            }
        }
        return true;
    }

    /**
     * Stores child URLs from the given set into the crawling queue for future processing.
     * This method filters out blank URLs and increments the depth for child URLs.
     *
     * @param urlQueue the parent URL queue item
     * @param childUrlSet the set of child URLs to be queued for crawling
     */

    /** Service for managing crawled document data */
    @Resource
    protected DataService<OpenSearchAccessResult> dataService;

    /** Service for managing URL crawling queue */
    @Resource
    protected UrlQueueService<OpenSearchUrlQueue> urlQueueService;

    /** Service for URL filtering operations */
    @Resource
    protected UrlFilterService urlFilterService;