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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-2362) Reduce blocking in client API (Tables)
Date Wed, 19 Feb 2014 20:08:21 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-2362?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13905996#comment-13905996
] 

Josh Elser commented on ACCUMULO-2362:
--------------------------------------

Thanks for the advice, [~kturner]. I think most of the time, the contention should only arise
when creating the objects (as opposed to reading data) as we don't re-fetch things like the
tableID, but this would be a good factor to include (creating the Scanner as opposed to creating
and reading data with a Scanner).

> Reduce blocking in client API (Tables)
> --------------------------------------
>
>                 Key: ACCUMULO-2362
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-2362
>             Project: Accumulo
>          Issue Type: New Feature
>          Components: client
>    Affects Versions: 1.4.4, 1.5.0
>            Reporter: Josh Elser
>             Fix For: 1.7.0
>
>
> Presently, the {{Tables}} class contains a static map of instance to ZooCache that *many*
of the classes in the client API use. The problem with this is that many of the methods on
ZooCache ultimately are synchronized. When multiple threads using Connectors, TableOperations,
Scanners/BatchScanners, and BatchWriters against the same Accumulo instance, you currently
have a massive synchronization problem.
> We should give some thought to heavy, concurrent access to Accumulo client API calls
within the same JVM. Consideration should also be given to the consistency of wrapping zookeeper
with a cache like is presently done.



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