Thread[] threads = new Thread[threadNum];
        ESSourceReader reader = new ESSourceReader(client, settings, indexName);
        reader.setScrollSize(100);
        for (int i = 0; i < threadNum; i++) {
            threads[i] = new Thread(() -> {
                Map<String, Object> source;
                while ((source = reader.read()) != null) {

/**
 * A {@link TransferListener} implementation that wraps another delegate {@link TransferListener} but makes it run
 * on single thread, keeping the listener logic simple. This listener also blocks on last transfer event to allow
 * output to perform possible cleanup. It spawns a daemon thread to consume queued events that may fall in even
 * concurrently.
 *
 * @since 4.0.0
 */

 * thread) the subscriber is actually called when an event is dispatched to it.
 *
 * @author Colin Decker
 */
@ElementTypesAreNonnullByDefault
abstract class Dispatcher {

  /**
   * Returns a dispatcher that queues events that are posted reentrantly on a thread that is already
   * dispatching an event, guaranteeing that all events posted on a single thread are dispatched to

        // for technical reasons we cannot throw here, even if delegate does cancel transfer
        listener.transferInitiated(event(session, resource, TransferEvent.EventType.INITIATED));

        Thread.sleep(500); // to make sure queue is processed, cancellation applied

        // subsequent call will cancel
        assertThrows(
                TransferCancelledException.class,

So we have a dedicated thread for every socket that just reads frames and dispatches them.

The reader thread must never run application-layer code. Otherwise one slow stream can hold up the entire connection.

        }
      }
    } finally {
      if (interrupted) {
        Thread.currentThread().interrupt();
      }
    }
  }

  /** Invokes {@code toJoin.}{@link Thread#join() join()} uninterruptibly. */
  @J2ktIncompatible
  @GwtIncompatible // concurrency
  public static void joinUninterruptibly(Thread toJoin) {
    boolean interrupted = false;
    try {
      while (true) {
        try {

Calls are executed in one of two ways:

 * **Synchronous:** your thread blocks until the response is readable.
 * **Asynchronous:** you enqueue the request on any thread, and get [called back](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-callback/) on another thread when the response is readable.

            SingletonLaContainerFactory.init();

            final Thread shutdownCallback = new Thread("ShutdownHook") {
                @Override
                public void run() {
                    destroyContainer();
                }

            };
            Runtime.getRuntime().addShutdownHook(shutdownCallback);

            commandThread = new Thread(() -> {

  }

  @SuppressWarnings("ThreadPriorityCheck") // TODO: b/175898629 - Consider onSpinWait.
  static void awaitWaiting(Thread t) {
    while (true) {
      Thread.State state = t.getState();
      switch (state) {
        case RUNNABLE:
        case BLOCKED:
          Thread.yield();
          break;
        case WAITING:
          return;
        default:

        }

        ClassLoader oldClassLoader = Thread.currentThread().getContextClassLoader();
        try {
            Thread.currentThread().setContextClassLoader(pluginDescriptor.getClassRealm());

            return container.lookup(role, roleHint);
        } finally {
            Thread.currentThread().setContextClassLoader(oldClassLoader);
        }
    }