Flink：端到端Exactly-Once

参考

1. https://flink.apache.org/features/2018/03/01/end-to-end-exactly-once-apache-flink.html
2. https://segmentfault.com/a/1190000019329884
3. https://www.jianshu.com/p/02d6d1103746
4. https://developer.51cto.com/article/643945.html
5. https://cwiki.apache.org/confluence/display/KAFKA/KIP-98+-+Exactly+Once+Delivery+and+Transactional+Messaging