Caused by: org.apache.flink.runtime.io.network.netty.exception.RemoteTransportException: Connecting to remote task manager 'IP:PORT' has failed. This might indicate that the remote task manager has been lost.

该问题的原因是 TaskManager挂了 或者 网络不通。

原因也有很多，比如该TM运行中OOM了，可以尝试增加下TM内存。