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From "Karthick Sankarachary (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3777) Redefine Identity Of HBase Configuration
Date Wed, 20 Apr 2011 01:50:06 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3777?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13021901#comment-13021901
] 

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

I took a stab at implementing the reference count in the {{HCM}}, but left the {{finalize}}
in there as a last line of defense. In order for this to work, every connection acquired through
{{HCM#getConnection}} must be closed when no longer needed. For more details, please take
a look at the V3 version of the patch. This time around, I ran the tests on a Linux box, and
saw a couple of test cases fail in {{TestReplication}} and {{TestHBaseTestingUtility}}, but
they were caused by some flaky file access issues.

> 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-V2.patch, HBASE-3777-V3.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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