前两天运到一个问题：standalone版本的flink，重启后，还没有运行任务，查看jobmanagement的日志，发现一直报如下错误。
2020-06-30 08:42:27,829 ERROR org.apache.flink.runtime.rest.handler.taskmanager.TaskManagerDetailsHandler - Unhandled exception.
org.apache.flink.runtime.resourcemanager.exceptions.UnknownTaskExecutorException: No TaskExecutor registered under dfd3b6386d13f514062ef0ad7a292069.
at org.apache.flink.runtime.resourcemanager.ResourceManager.requestTaskManagerInfo(ResourceManager.java:585)
at sun.reflect.GeneratedMethodAccessor54.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.handleRpcInvocation(AkkaRpcActor.java:274)
at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.handleRpcMessage(AkkaRpcActor.java:189)
at org.apache.flink.runtime.rpc.akka.FencedAkkaRpcActor.handleRpcMessage(FencedAkkaRpcActor.java:74)
at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.onReceive(AkkaRpcActor.java:147)
at org.apache.flink.runtime.rpc.akka.FencedAkkaRpcActor.onReceive(FencedAkkaRpcActor.java:40)
at akka.actor.UntypedActor$$anonfun$receive$1.applyOrElse(UntypedActor.scala:165)
at akka.actor.Actor$class.aroundReceive(Actor.scala:502)
at akka.actor.UntypedActor.aroundReceive(UntypedActor.scala:95)
at akka.actor.ActorCell.receiveMessage(ActorCell.scala:526)
at akka.actor.ActorCell.invoke(ActorCell.scala:495)
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:257)
at akka.dispatch.Mailbox.run(Mailbox.scala:224)
at akka.dispatch.Mailbox.exec(Mailbox.scala:234)
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
开始以为是flink的savepoint和checkpoint的功能，所以，kill-9 把flink的jm和tm都杀掉，然后把/tmp等目录都删除，再次使用/flink/bin/start-cluster.sh启动，查看jm日志还是会报错。
解决办法：问题原因是因为有旧的Taskmanager页面打开，但是没有关闭，所以找不到对应的TaskExecutor,解决办法是关闭页面即可。Flink官方不处理这个问题。
参考:https://issues.apache.org/jira/browse/Flink-8929
