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From "Geoffrey Jacoby (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (PHOENIX-4021) Remove CachingHTableFactory
Date Fri, 14 Jul 2017 02:01:05 GMT

     [ https://issues.apache.org/jira/browse/PHOENIX-4021?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Geoffrey Jacoby updated PHOENIX-4021:
-------------------------------------
    Attachment: PHOENIX-4021.patch

Attaching this first draft patch for discussion. It removes CachingHTableFactory but does
not replace it with any coprocessor HConnection caching, so while this will solve the potential
race condition, there might be a performance regression from making new HConnections each
time.

[~samarthjain], [~vincentpoon] [~jamestaylor], your thoughts on how best to make the server->server
RPCs cache HConnections? Perhaps something like PHOENIX-3611, but simpler and for HConnections
rather than ConnectionQueryServices?

> 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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