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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-12117) Constructors that use Configuration may be harmful
Date Tue, 30 Sep 2014 02:26:33 GMT
Andrew Purtell created HBASE-12117:

             Summary: 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.) HConnections 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 total on CPU time. This is just one example
where constructors that use Configuration may be harmful.

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