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From "M. C. Srivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3777) Redefine Identity Of HBase Configuration
Date Fri, 29 Apr 2011 03:20:03 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3777?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13026821#comment-13026821
] 

M. C. Srivas commented on HBASE-3777:
-------------------------------------

It seems error-prone to compare conf's to identify clusters.

The mapping should really be "cluster uuid" (if such a thing exists) to connection. Perhaps
there's a hmaster md5 that can be used in lieu of cluster-uuid sitting in ZK that can be probed?

Then, an alternative other way is to go ahead and make the extra connection and use it to
determine which cluster the client is going against. If it's a previously-seen cluster, close
this newly-created connection, and use the stashed one. Else this is a new cluster and create
a new mapping entry.




> Redefine Identity Of HBase Configuration
> ----------------------------------------
>
>                 Key: HBASE-3777
>                 URL: https://issues.apache.org/jira/browse/HBASE-3777
>             Project: HBase
>          Issue Type: Improvement
>          Components: client, ipc
>    Affects Versions: 0.90.2
>            Reporter: Karthick Sankarachary
>            Assignee: Karthick Sankarachary
>            Priority: Minor
>             Fix For: 0.92.0
>
>         Attachments: 3777-TOF.patch, HBASE-3777-V2.patch, HBASE-3777-V3.patch, HBASE-3777-V4.patch,
HBASE-3777-V6.patch, HBASE-3777.patch
>
>
> Judging from the javadoc in {{HConnectionManager}}, sharing connections across multiple
clients going to the same cluster is supposedly a good thing. However, the fact that there
is a one-to-one mapping between a configuration and connection instance, kind of works against
that goal. Specifically, when you create {{HTable}} instances using a given {{Configuration}}
instance and a copy thereof, we end up with two distinct {{HConnection}} instances under the
covers. Is this really expected behavior, especially given that the configuration instance
gets cloned a lot?
> Here, I'd like to play devil's advocate and propose that we "deep-compare" {{HBaseConfiguration}}
instances, so that multiple {{HBaseConfiguration}} instances that have the same properties
map to the same {{HConnection}} instance. In case one is "concerned that a single {{HConnection}}
is insufficient for sharing amongst clients",  to quote the javadoc, then one should be able
to mark a given {{HBaseConfiguration}} instance as being "uniquely identifiable".
> Note that "sharing connections makes clean up of {{HConnection}} instances a little awkward",
unless of course, you apply the change described in HBASE-3766.

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