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https://issues.apache.org/jira/browse/YARN-6102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15825734#comment-15825734
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Naganarasimha G R commented on YARN-6102:
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Good catch [~ajithshetty],
But i would not recommend the first approach here as the problem is older
services in RM's active service if it refer to the newer Async dispatcher then
state of the services will not be proper. I would prefer to go with the 2nd
approach itself and as well we might need to handle for all the active
services, i.e. dispatcher should be saved durign the init and refer to it
rather than getting it from {{rmContext}}.
> 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
>
> {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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