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From "James Taylor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-4021) Remove CachingHTableFactory
Date Fri, 14 Jul 2017 18:03:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4021?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16087702#comment-16087702
] 

James Taylor commented on PHOENIX-4021:
---------------------------------------

bq. the RegionCoprocessorEnvironment that is passed in to the setup method already has the
right config setup in there.
Great! Yep, I missed that.

I think this patch is good to go, then. I agree - perf testing should be done (but is planned
already). I think we should check this in to all branches. Nice work, [~gjacoby]. Have you
kicked off a test run yet?

> Remove CachingHTableFactory
> ---------------------------
>
>                 Key: PHOENIX-4021
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4021
>             Project: Phoenix
>          Issue Type: Bug
>    Affects Versions: 4.11.0
>            Reporter: Geoffrey Jacoby
>            Assignee: Geoffrey Jacoby
>              Labels: globalMutableSecondaryIndex
>             Fix For: 4.12.0
>
>         Attachments: PHOENIX-4021.patch
>
>
> CachingHTableFactory is used as a performance optimization when writing to global indexes
so that HTable instances are cached and later automatically cleaned up, rather than instantiated
each time we write to an index.
> This should be removed for two reasons:
> 1. It opens us up to race conditions, because HTables aren't threadsafe, but CachingHTableFactory
doesn't guard against two threads both grabbing the same HTable and using it simultaneously.
Since all ops going through a region share the same IndexWriter and ParallelWriterIndexCommitter,
and hence the same CachingHTableFactory, that means separate operations can both be holding
the same HTable. 
> 2. According to discussion on PHOENIX-3159, and offline discussions I've had with [~apurtell],
HBase 1.x and above make creating throwaway HTable instances cheap so the caching is no longer
needed.
> For 4.x-HBase-1.x and master, we should remove CachingHTableFactory, and for 4.x-HBase-0.98,
we should either get rid of it (if it's not too much of a perf hit) or at least make it threadsafe.



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