[jira] [Commented] (YARN-6102) On failover RM can crash due to unregistered event to AsyncDispatcher

["Rohith Sharma K S (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-6102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16075932#comment-16075932 ] 

Rohith Sharma K S commented on YARN-6102:
-----------------------------------------

thanks [~ajithshetty] and [~Naganarasimha] for explanation.

bq. Stopping of service will not stop the rpc thread handling the current event/call
ahh .. I see.. then as a solution need to ensure RPC threads are stopped before return from service stop method. 

[~ajithshetty] would you change your patch to ensuring RPC threads are stopped? This will common solution for all such race condition issues. 

> On failover RM can crash due to unregistered event to AsyncDispatcher
> ---------------------------------------------------------------------
>
>                 Key: YARN-6102
>                 URL: https://issues.apache.org/jira/browse/YARN-6102
>             Project: Hadoop YARN
>          Issue Type: Bug
>    Affects Versions: 2.8.0, 2.7.3
>            Reporter: Ajith S
>            Assignee: Ajith S
>            Priority: Critical
>         Attachments: eventOrder.JPG
>
>
> {code}2017-01-17 16:42:17,911 FATAL [AsyncDispatcher event handler] event.AsyncDispatcher (AsyncDispatcher.java:dispatch(200)) - Error in dispatcher thread
> java.lang.Exception: No handler for registered for class org.apache.hadoop.yarn.server.resourcemanager.rmnode.RMNodeEventType
>         at org.apache.hadoop.yarn.event.AsyncDispatcher.dispatch(AsyncDispatcher.java:196)
>         at org.apache.hadoop.yarn.event.AsyncDispatcher$1.run(AsyncDispatcher.java:120)
>         at java.lang.Thread.run(Thread.java:745)
> 2017-01-17 16:42:17,914 INFO  [AsyncDispatcher ShutDown handler] event.AsyncDispatcher (AsyncDispatcher.java:run(303)) - Exiting, bbye..{code}
> The same stack i was also noticed in {{TestResourceTrackerOnHA}} exits abnormally, after some analysis, i was able to reproduce.
> Once the nodeHeartBeat is sent to RM, inside {{org.apache.hadoop.yarn.server.resourcemanager.ResourceTrackerService.nodeHeartbeat(NodeHeartbeatRequest)}}, before sending it to dispatcher through
> {{this.rmContext.getDispatcher().getEventHandler().handle(nodeStatusEvent);}} if RM failover is called, the dispatcher is reset
> The new dispatcher is however first started and then the events are registered at {{org.apache.hadoop.yarn.server.resourcemanager.ResourceManager.reinitialize(boolean)}}
> So event order will look like
> 1. Send Node heartbeat to {{ResourceTrackerService}}
> 2. In {{ResourceTrackerService.nodeHeartbeat}}, before passing to dispatcher call RM failover
> 3. In RM Failover, current active will reset dispatcher @reinitialize i.e ( {{resetDispatcher();}} + {{createAndInitActiveServices();}} )
> Now between {{resetDispatcher();}} and {{createAndInitActiveServices();}} , the {{ResourceTrackerService.nodeHeartbeat}} invokes dipatcher
> This will cause the above error as at point of time when {{STATUS_UPDATE}} event is given to dispatcher in {{ResourceTrackerService}} , the new dispatcher(from the failover) may be started but not yet registered for events
> Using same steps(with pausing JVM at debug), i was able to reproduce this in production cluster also. for {{STATUS_UPDATE}} active service event, when the service is yet to forward the event to RM dispatcher but a failover is called and dispatcher reset is between {{resetDispatcher();}} & {{createAndInitActiveServices();}}



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