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From "Nate Cole" <nc...@hortonworks.com>
Subject Re: Review Request 36895: Cluster creates stuck at 9x% (deadlock sql exception)
Date Thu, 30 Jul 2015 01:36:05 GMT

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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/36895/#review93535
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Ship it!


Ship It!

- Nate Cole


On July 29, 2015, 9:11 p.m., Jonathan Hurley wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/36895/
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> 
> (Updated July 29, 2015, 9:11 p.m.)
> 
> 
> Review request for Ambari, Alejandro Fernandez, Nate Cole, and Sumit Mohanty.
> 
> 
> Bugs: AMBARI-12570
>     https://issues.apache.org/jira/browse/AMBARI-12570
> 
> 
> Repository: ambari
> 
> 
> Description
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> 
> Similar to AMBARI-12526, Ambari installation via a blueprint on SQL Azure gets stuck
somewhere between 90% and 100% because of a SQL Database deadlock.
> 
> - We have dual X-locks on hostcomponentstate asking for U-locks when updating the CLUSTERED
INDEX.
> - Both dual X-locks, from different transactions and different processes, are on the
same row (technically impossible) - based on the XML execution plan, we can see that the concurrent
UPDATE statements are executing on different rows due to their CLUSTERED INDEX predicate.
> - In Java, Ambari has locks which prevent concurrent U- or X-locks on the same row
> - Only happens on SQL Server
> 
> My best suspicion right now is that we have a key hash collision happening on this table.
That's why two processes appear to have the same lock even though they are on different rows.
> 
> Restricting row-level locking on this table will prevent locking on hash keys which could
collide.
> 
> 
> Diffs
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> 
>   ambari-server/src/main/resources/Ambari-DDL-SQLServer-CREATE.sql 0ff1aff 
> 
> Diff: https://reviews.apache.org/r/36895/diff/
> 
> 
> Testing
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> 
> Deployed a clean cluster on SQL Server and then ran 10+ deployments on SQL Azure without
seeing a deadlock.
> 
> 
> Thanks,
> 
> Jonathan Hurley
> 
>


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