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From "Andrzej Bialecki (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-12833) Use timed-out lock in DistributedUpdateProcessor
Date Tue, 23 Apr 2019 13:02:00 GMT

    [ https://issues.apache.org/jira/browse/SOLR-12833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16824104#comment-16824104
] 

Andrzej Bialecki  commented on SOLR-12833:
------------------------------------------

Looking closer at the code I don't think it can be easily refactored to use two implementations
of VersionBucket (I'd love to be proven wrong, though!) - since the only way to use the intrinsic
object monitor is by using {{synchronized}} keyword around a block the usage would become
very complicated, basically we would have to factor out two almost identical methods for each
of the sections where bucket locking is used.

So I guess for now the solution for that use case is to drastically reduce the number of buckets.

> Use timed-out lock in DistributedUpdateProcessor
> ------------------------------------------------
>
>                 Key: SOLR-12833
>                 URL: https://issues.apache.org/jira/browse/SOLR-12833
>             Project: Solr
>          Issue Type: Improvement
>      Security Level: Public(Default Security Level. Issues are Public) 
>          Components: update, UpdateRequestProcessors
>    Affects Versions: 7.5, 8.0
>            Reporter: jefferyyuan
>            Assignee: Mark Miller
>            Priority: Minor
>             Fix For: 7.7, 8.0
>
>         Attachments: SOLR-12833-noint.patch, SOLR-12833.patch, SOLR-12833.patch
>
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> There is a synchronize block that blocks other update requests whose IDs fall in the
same hash bucket. The update waits forever until it gets the lock at the synchronize block,
this can be a problem in some cases.
>  
> Some add/update requests (for example updates with spatial/shape analysis) like may take
time (30+ seconds or even more), this would the request time out and fail.
> Client may retry the same requests multiple times or several minutes, this would make
things worse.
> The server side receives all the update requests but all except one can do nothing, have
to wait there. This wastes precious memory and cpu resource.
> We have seen the case 2000+ threads are blocking at the synchronize lock, and only a
few updates are making progress. Each thread takes 3+ mb memory which causes OOM.
> Also if the update can't get the lock in expected time range, its better to fail fast.
>  
> We can have one configuration in solrconfig.xml: updateHandler/versionLock/timeInMill,
so users can specify how long they want to wait the version bucket lock.
> The default value can be -1, so it behaves same - wait forever until it gets the lock.



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