@Override
  public void start() {
    if (!this.isRunning.compareAndSet(false, true)) {
      LOG.warn("Tried to start, but already started");
    } else {
      this.httpServer.start();
      LOG.info("Started http server");
    }
  }
Runs an {@link HttpServer} to communicate with workers.
samza-core/src/main/java/org/apache/samza/coordinator/communication/HttpCoordinatorCommunication.java