@Override
  public void stop() {
    if (!this.isRunning.compareAndSet(true, false)) {
      LOG.warn("Tried to stop, but not currently running");
    } else {
      this.httpServer.stop();
      LOG.info("Stopped http server");
    }
  }
Runs an {@link HttpServer} to communicate with workers.
samza-core/src/main/java/org/apache/samza/coordinator/communication/HttpCoordinatorCommunication.java