@Override
                public void onMessageSent(MessageSentResult result) {
                    if (!result.isSuccess()) {
                        resendEvent(es);
                    }
                }
fetch message, wait if queue is empty

@return EventStat
@throws Exception
inlong-tubemq/tubemq-connectors/tubemq-connector-flume/src/main/java/org/apache/flume/sink/tubemq/TubemqSink.java