[jira] [Commented] (PHOENIX-4021) Remove CachingHTableFactory

["Kang Yuan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PHOENIX-4021?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16171811#comment-16171811 ] 

Kang Yuan commented on PHOENIX-4021:
------------------------------------

we backport this patch to phoenix4.11-HBase-0.98 .The performance go down a lot when CachineHTableFactory is disabled, so many HTables were been created and used once.It's wast and lower the performance 
can we make CachingHTableFactory thread safe instead of removing it

> 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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