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