private final ConcurrentHashMap<String, AtomicInteger> hostnames = new ConcurrentHashMap<>();
  private final int hostLimit;

  public Crawler(OkHttpClient client, int queueLimit, int hostLimit) {
    this.client = client;
    this.queue = new LinkedBlockingQueue<>(queueLimit);
    this.hostLimit = hostLimit;
  }

  private void parallelDrainQueue(int threadCount) {
    ExecutorService executor = Executors.newFixedThreadPool(threadCount);

type ConsoleLogger struct {
	Enable bool `json:"enable"`
}

// serverConfigV33 is just like version '32', removes clientID from NATS and MQTT, and adds queueDir, queueLimit in all notification targets.
type serverConfigV33 struct {
	quick.Config `json:"-"` // ignore interfaces

	Version string `json:"version"`

	// S3 API configuration.
	Credential auth.Credentials `json:"credential"`