tillrohrmann opened a new pull request #11683: [FLINK-15347] Add 
SupervisorActor which monitors the proper termination of AkkaRpcActors
URL: https://github.com/apache/flink/pull/11683
 
 
   
   ## What is the purpose of the change
   
   In order to properly complete the termination future of an RpcEndpoint, we 
need to monitor
   when the underlying AkkaRpcActor has been removed from the ActorSystem. If 
this is not done,
   then it can happen that another RpcEndpoint using the same name cannot be 
started because
   the old RpcEndpoint is still registered.
   
   The way we achieve this monitoring is to introduce a helper actor which is 
responsible for
   starting the AkkaRpcActors for all RpcEndpoints. Since the SupervisorActor 
is the parent
   of all RpcEndpoints, it can tell when they are being removed from the 
ActorSystem through
   the SupervisorStrategy.
   
   A consequence of the new actor is that the akka urls change from 
akka://flink@actorsystem:port/user/xyz
   to akka://flink@actorsystem:port/user/rpc/xyz. The respective method 
AkkaRpcServiceUtils.getRpcUrl
   has been updated to reflect this change. This hierarchy change also warrants 
the bump of the
   AkkaRpcService.VERSION.
   
   The failure behaviour of the underlying ActorSystem has been changed so that 
it terminates
   all running actors if an exception is thrown from the SupervisorActor. The 
assumption is that
   such an exception always indicates a programming error and is unrecoverable.
   
   The same applies to failure originating from an AkkaRpcActor (children of 
the SupervisorActor).
   If such an exception is thrown, then we assume that the system is in an 
illegal state and shut it
   down. The way it works is by recording the failure cause for the respective 
AkkaRpcActor and
   then terminating the ActorSystem.
   
   ## Verifying this change
   
   - Added `AkkaActorSystemTest`, `SupervisorActorTest` and 
`AkkaRpcActorTest.canReuseEndpointNameAfterTermination`.
   
   ## Does this pull request potentially affect one of the following parts:
   
     - Dependencies (does it add or upgrade a dependency): (no)
     - The public API, i.e., is any changed class annotated with 
`@Public(Evolving)`: (no)
     - The serializers: (no)
     - The runtime per-record code paths (performance sensitive): (no)
     - Anything that affects deployment or recovery: JobManager (and its 
components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: (yes)
     - The S3 file system connector: (no)
   
   ## Documentation
   
     - Does this pull request introduce a new feature? (no)
     - If yes, how is the feature documented? (not applicable)
   

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