https://stackoverflow.com/questions/50972168/flink-latency-metrics-not-being-shown/50982071#50982071
https://stackoverflow.com/questions/45211970/how-to-get-the-latency-number-of-flink-job
https://www.slideshare.net/dataArtisans/apache-flink-training-metrics-monitoring
原文：https://www.cnblogs.com/WCFGROUP/p/9499305.html