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https://issues.apache.org/jira/browse/PHOENIX-4021?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16086739#comment-16086739
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Samarth Jain commented on PHOENIX-4021:
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Before we go down the route of caching an HConnection, it would be good to
confirm that if an HConnection gets into a funky state, then internal logic
will get it back in a usable state (through retries, establishing new ZK
session, etc.)
> 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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