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https://issues.apache.org/jira/browse/HBASE-12117?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14153312#comment-14153312
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Andrew Purtell commented on HBASE-12117:
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Yeah I don't think HTable is as lightweight as we want because if an app
manages its own HConnection and creates an HTable for each interaction - as we
recommend - then it can pay this unexpected cost as much as ~20% of CPU time.
This is one example where using Configuration to set up an object is expensive.
Found this when looking at something else.
Yes I think we could cache configuration in Connection. We are using it like a
factory for HTable. Object factories would one way to address this
(anti?)pattern wherever it's costly.
Related, we should also create by reflection once and cache the desired
RpcController object, and clone it for new HTables for the Connection.
> 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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