protected void checkForSendCallbackErrors(String msg) {
    // Check for send errors
    Throwable sendThrowable = sendExceptionOnCallback.get();
    if (sendThrowable != null) {
      LOG.error(msg, sendThrowable);
      throw new SamzaException(msg, sendThrowable);
    }
  }
This method is used to check whether there were any previous exceptions in the send call backs.
And if any exception occurs the producer is considered to be stuck/broken
@param msg the msg that is passed to the exception.
samza-azure/src/main/java/org/apache/samza/system/eventhub/producer/AsyncSystemProducer.java