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From "Micah Whitacre (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6341) Publicly expose HConnectionKey
Date Fri, 06 Jul 2012 21:32:35 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6341?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13408366#comment-13408366
] 

Micah Whitacre commented on HBASE-6341:
---------------------------------------

As I indicated above the common use case we have is to maintain a cache of Configuration ->
HTablePool instances.  In the our processing infrastructure (Storm) Hadoop Configuration objects
are serialized and passed into the processing workers.  Instead of creating new HTable instances
we'd like to reuse HTablePool instances to retrieve existing HTableInterface instances.  Since
the Configuration objects are new instances we can't use a Map<Configuration, HTablePool>
to reuse HTablePool instances and HConnectionKey would fill that gap nicely.  Additionally
if we don't cache HTablePool instances we'd lose the benefit of reusing connections because
we'd end up with multiple HTablePool instances containing one pooled table.

We have other similar higher order constructs which take a Configuration and it would be nice
to reuse instances which interact with the same underlying HBaseTableInterface/Pool instance.
 

I've seen this elsewhere in discussions but essentially we need an efficient way to identify
a Configuration object represents the same underlying HBase cluster.  I don't have a link
handy but I remember seeing conversations which talked about adding a "uniquifier" to Configuration
and I perceived the HConnectionKey to be the resolution to that.  If there is a better solution
for solving that I'd be willing to adopt that.
                
> Publicly expose HConnectionKey
> ------------------------------
>
>                 Key: HBASE-6341
>                 URL: https://issues.apache.org/jira/browse/HBASE-6341
>             Project: HBase
>          Issue Type: Improvement
>          Components: client
>    Affects Versions: 0.92.0
>            Reporter: Micah Whitacre
>            Priority: Trivial
>         Attachments: hbase_6341.patch
>
>
> HBASE-3777 introduced the concept of a HConnectionKey to quickly identify and compare
Configuration instances which lack equals/hashCode values.
> We currently have use cases where being able to key Configuration objects in a similar
way would be helpful.  An example of this would be maintain a cache of  HTablePool instances
based on the HConnectionKey instead of the Configuration instance.
> I propose that HConnectionKey be made publicly available instead of its current package
scope.  Or another possibility would be to move it from being a static inner class to being
part of the API.

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