protected boolean isRunning() {
    return running.get();
  }
Information on whether this instance is accepting requests and responses. This will return {@code false} as soon as
{@link #shutdown(long, TimeUnit)} is called whether or not the instance has actually stopped working.
@return {@code true} if in a state to receive requests/responses. {@code false} otherwise.
ambry-rest/src/main/java/com/github/ambry/rest/AsyncRequestResponseHandler.java