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https://issues.apache.org/jira/browse/YARN-2946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14245794#comment-14245794
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Jian He commented on YARN-2946:
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bq. For all above mentioned method's causing deadlock , introduce StateMachine
in RMStateStore like handling application store. So all the execution flows
from StateMachine->zkRMStateStore.class.
I think this is a reasonable way. We can call the transitions synchronously in
each storeToken or storeMasterKey methods. This way we make all store
operations follow the same path - all going through state machines
> DeadLocks in RMStateStore<->ZKRMStateStore
> ------------------------------------------
>
> Key: YARN-2946
> URL: https://issues.apache.org/jira/browse/YARN-2946
> Project: Hadoop YARN
> Issue Type: Bug
> Components: resourcemanager
> Affects Versions: 2.7.0
> Reporter: Rohith
> Assignee: Rohith
> Priority: Blocker
> Attachments: 0001-YARN-2946.patch, 0002-YARN-2946.patch,
> RM_BeforeFix_Deadlock_cycle_1.png, RM_BeforeFix_Deadlock_cycle_2.png,
> TestYARN2946.java
>
>
> Found one deadlock in ZKRMStateStore.
> # Initial stage zkClient is null because of zk disconnected event.
> # When ZKRMstatestore#runWithCheck() wait(zkSessionTimeout) for zkClient to
> re establish zookeeper connection either via synconnected or expired event,
> it is highly possible that any other thred can obtain lock on
> {{ZKRMStateStore.this}} from state machine transition events. This cause
> Deadlock in ZKRMStateStore.
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