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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12117) Constructors that use Configuration may be harmful
Date Tue, 30 Sep 2014 06:54:33 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12117?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14152872#comment-14152872
] 

stack commented on HBASE-12117:
-------------------------------

So the focus is on 17% of overall CPU -- the finishSetup of HTable -- and of this most is
just getting Configuration.  Yuck.  This is our making an HTable instance per session?  We
keep it around?  HTable ain't that lightweight then?  Any chance of caching some config in
Connection for instance?

> Constructors that use Configuration may be harmful
> --------------------------------------------------
>
>                 Key: HBASE-12117
>                 URL: https://issues.apache.org/jira/browse/HBASE-12117
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Andrew Purtell
>         Attachments: traces.client.c.svg, traces.client.getHTable.svg
>
>
> There's a common pattern in HBase code where in the constructor, or in an initialization
method also called once per instantiation, or both, we look up values from Hadoop Configuration
and store them into fields. This can be expensive if the object is frequently created. Configuration
is a heavyweight registry that does a lot of string operations and regex matching. See attached
example. Method calls into Configuration account for 48.25% of CPU time when creating the
HTable object in 0.98. (The remainder is spent instantiating the RPC controller via reflection,
a separate issue that merits followup elsewhere.) Creation of HTable instances is expected
to be a lightweight operation if a client is using unmanaged HConnections; however creating
HTable instances takes up about 18% of the client's total on-CPU time. This is just one example
where constructors that use Configuration may be harmful.



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