// we want to see all top-level thread groups
        ThreadGroup tg = Thread.currentThread().getThreadGroup();
        while (tg.getParent() == null) {
            tg = tg.getParent();
        }

        ThreadGroup[] tgList = new ThreadGroup[tg.activeGroupCount()];
        tg.enumerate(tgList);

        boolean seen = false;

        for (ThreadGroup aTgList : tgList) {

            bigThreadConstructor.newInstance(
                (ThreadGroup) null, finalizer, threadName, defaultStackSize, inheritThreadLocals);
      } catch (Throwable t) {
        logger.log(
            Level.INFO, "Failed to create a thread without inherited thread-local values", t);
      }
    }
    if (thread == null) {
      thread = new Thread((ThreadGroup) null, finalizer, threadName);
    }
    thread.setDaemon(true);

    protected boolean background = false;

    protected boolean daemon = false;

    protected int threadPriority = Thread.NORM_PRIORITY;

    protected Thread parentThread;

    protected ThreadGroup crawlerThreadGroup;

    public Crawler() {
        crawlerContext = new CrawlerContext();
        final SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmssSSS", Locale.ENGLISH);

    }

    /**
     * ThreadCreator for creating daemon threads with fixed ThreadGroup-name.
     */
    @Deprecated
    static final class DaemonThreadCreator implements ThreadFactory {
        static final String THREADGROUP_NAME = "org.apache.maven.artifact.resolver.DefaultArtifactResolver";

        static final ThreadGroup GROUP = new ThreadGroup(THREADGROUP_NAME);