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From "Karthick Sankarachary (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3777) Redefine Identity Of HBase Configuration
Date Fri, 15 Apr 2011 00:48:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3777?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13020134#comment-13020134
] 

Karthick Sankarachary commented on HBASE-3777:
----------------------------------------------

{quote}Suppose client A comes with config and places an entry in HBASE_INSTANCES. Then client
B comes with config, the previous entry would be returned to client B.
Now client A modifies one of the connection-specific properties - resulting in a change of
the HConnectionKey for client B.{quote}

Ah, I see. By freezing the config in the key, we ensure that subsequent changes to the config
will only affect the client that is making that change. I will update the patch to do that
momentarily. 

> 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: 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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