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From "Prasanth Jayachandran (Jira)" <>
Subject [jira] [Commented] (HIVE-22687) Query hangs indefinitely if LLAP daemon registers after the query is submitted
Date Fri, 06 Mar 2020 09:11:00 GMT


Prasanth Jayachandran commented on HIVE-22687:

I was able to repro this issue recently and tested this patch but the patch doesn't seem to
help. Even if the order of slot znode and worker znode is changed the notification of slot
znode is not received by the AM and hence it does not populate the map. 

For the query that failed to get scheduled I see this
No zookeeper data for path
NODE_ADDED for zknode ..../workers/worker-0000000000 {code}
For the query that succeeded I see this
NODE_ADDED for zknode ..../workers/worker-0000000000 
NODE_ADDED for zknode ..../workers/worker-0000000000  {code}
"No zookeeper data for path" seem to indicate there is a lost notification for the slot znode. 

> Query hangs indefinitely if LLAP daemon registers after the query is submitted
> ------------------------------------------------------------------------------
>                 Key: HIVE-22687
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>          Components: llap
>    Affects Versions: 3.1.0
>            Reporter: Himanshu Mishra
>            Assignee: Himanshu Mishra
>            Priority: Major
>         Attachments: HIVE-22687.01.patch, HIVE-22687.02.patch
> If a query is submitted and no LLAP daemon is running, it waits for 1 minute and times
out with error {{SERVICE_UNAVAILABLE}}.
> While waiting, if a new LLAP Daemon starts, then the timeout is cancelled, and the tasks
do not get scheduled as well. As a result, the query hangs indefinitely.
> This is due to the race condition where LLAP Daemon first registers the LLAP instance
at {{.../workers/worker-0000}}, and afterwards registers {{.../workers/slot-0000}}. In the
gap between two, Tez AM gets notified of worker zk node and while processing it checks if
slot zk node is present, if not it rejects the LLAP Daemon. Error in Tez AM is:
> {code:java}
> [INFO] [LlapScheduler] |impl.LlapZookeeperRegistryImpl|: Unknown slot for 8ebfdc45-0382-4757-9416-52898885af90{code}

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