private void waitForResponseHandlerThreadExit() {
    for (OperationController oc : ocList) {
      try {
        oc.getRequestResponseHandlerThread().join(SHUTDOWN_WAIT_MS);
      } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
      }
    }
  }
Wait for all the threads to finish up.
ambry-router/src/main/java/com/github/ambry/router/NonBlockingRouter.java