Rationale for making ParrotServerService.shutdown() async

[Michael Diamant]

In my RecordProcessor implementation, I override shutdown() to capture stats from local Ostrich webserver.  I discovered that at times, seemingly haphazardly, statistics were not captured.  I traced the root cause of the issue to be the 'oneway' modifier on the ParrotServerService.shutdown() definition.  I understand the 'oneway' Thrift modifier causes an RPC call to be async.  For my use case, I believe the parrot-server is shutdown before the stats logic can be captured because the invoker of shutdown() does not await a response.

I changed the Thrift definition from:  

oneway void shutdown()

to:

void shutdown()

This makes shutdown() invocations synchronous and addresses my problem (i.e. stats are captured via shutdown hook).  This change results in a parrot-feeder exception at shutdown.  It appears the exception is harmless and I haven't had time to investigate further.  Here is the exception:

ERR [20130626-13:18:12.682] util: Error shutting down Parrot: com.twitter.finagle.ChannelClosedException

ERR [20130626-13:18:12.682] util: com.twitter.finagle.ChannelClosedException: ChannelException at remote address: localhost/127.0.0.1:9999

ERR [20130626-13:18:12.682] util:     at com.twitter.finagle.NoStacktrace(Unknown Source) 

What was the rationale behind marking shutdown() 'oneway'?  The justification that comes to mind is to ensure nothing blocks during shutdown (i.e. parrot-server shutdown() is not intended to be long-running).  If that's the case, is there a better way to instrument capturing stats at shutdown?

If making the shutdown() call synchronous is the way to go, I can clean up the exception I show above and send a pull request.  I appreciate the team's responsiveness. 

Michael

[James Waldrop]

We (I) shouldn't have used oneway. It's an artifact of my newness to Thrift. That said we (Tom) have some changes coming Real Soon Now that should be integrated. It improves shutdown behavior a lot. 

—
http://twitter.com/HiveTheory

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[Michael Diamant]

Sounds good.  I'll use my fork until the changes are released.  Thank you for the quick reply.