.containsExactly(
            i1,
            i2,
            i3, // Integer subscribers are dispatched to first.
            s1,
            s2, // Though each integer subscriber dispatches to all string subscribers,
            s1,
            s2, // those string subscribers aren't actually dispatched to until all integer
            s1,
            s2 // subscribers have finished.
            )

        .containsExactly(
            i1,
            i2,
            i3, // Integer subscribers are dispatched to first.
            s1,
            s2, // Though each integer subscriber dispatches to all string subscribers,
            s1,
            s2, // those string subscribers aren't actually dispatched to until all integer
            s1,
            s2 // subscribers have finished.
            )

  }

  /**
   * Returns a dispatcher that dispatches events to subscribers immediately as they're posted
   * without using an intermediate queue to change the dispatch order. This is effectively a
   * depth-first dispatch order, vs. breadth-first when using a queue.
   */
  static Dispatcher immediate() {
    return ImmediateDispatcher.INSTANCE;
  }

  /** Dispatches the given {@code event} to the given {@code subscribers}. */

    checkNotNull(label, "label");
    synchronized (listeners) {
      for (PerListenerQueue<L> queue : listeners) {
        queue.add(event, label);
      }
    }
  }

  /**
   * Dispatches all events enqueued prior to this call, serially and in order, for every listener.
   *
   * <p>Note: this method is idempotent and safe to call from any thread
   */
  public void dispatch() {

import org.apache.maven.eventspy.EventSpy;
import org.apache.maven.execution.ExecutionListener;
import org.eclipse.aether.RepositoryListener;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Dispatches callbacks to all registered EventSpies.
 * @since 3.0.2
 */
@Named
@Singleton
public class EventSpyDispatcher {
    private final Logger logger = LoggerFactory.getLogger(getClass());

    this.bus = bus;
    this.target = checkNotNull(target);
    this.method = method;
    method.setAccessible(true);

    this.executor = bus.executor();
  }

  /** Dispatches {@code event} to this subscriber using the proper executor. */
  final void dispatchEvent(Object event) {
    executor.execute(
        () -> {
          try {
            invokeSubscriberMethod(event);

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.