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https://issues.apache.org/jira/browse/HBASE-3899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13078398#comment-13078398
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jirapos...@reviews.apache.org commented on HBASE-3899:
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/1257/
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(Updated 2011-08-02 20:00:02.348642)
Review request for hbase.
Changes
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Todd, Gary, thanks for the review. I agree that returnValue is less likely to
cause confusion. Summary of what changed in second iteration:
* change 'response' to 'returnValue' where appropriate;
* 'isReturnValueDelayed' is now a method in the Delayable interface -- if all
Delayables take the boolean parameter, all of them should expose this method;
* boolean parameter has the same semantics in all calls -- previously it was
'isRetValDelayed' and 'setRetValImmediately', which wasn't really a good idea :)
Summary
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Some use cases of delayed RPCs need the ability to delay the call until a
further moment, but set the return value immediately. For example, if a
handler calls a function returning void that might delay (a sync), the result
does not depend on the function's result (since it has none). This patch
enables that by making the following changes:
* change the Delayable interface so that startDelay specifies whether the
return value should be set immediately after call return or at the end of the
delay;
* make HBaseServer work according to the new semantics;
* add a unit test. We now have testDelayedRpc{Immediate,Delayed}Response,
testing that immediate and delayed return values work.
Please review, thanks!
This addresses bug HBASE-3899.
https://issues.apache.org/jira/browse/HBASE-3899
Diffs (updated)
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src/main/java/org/apache/hadoop/hbase/ipc/Delayable.java f2ae31e
src/main/java/org/apache/hadoop/hbase/ipc/HBaseServer.java 2f7dfae
src/test/java/org/apache/hadoop/hbase/ipc/TestDelayedRpc.java 60777cf
Diff: https://reviews.apache.org/r/1257/diff
Testing
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Since the code is not used yet, it does not affect other areas of the codebase.
Running unit tests as we speak.
Thanks,
Vlad
> enhance HBase RPC to support free-ing up server handler threads even if
> response is not ready
> ---------------------------------------------------------------------------------------------
>
> Key: HBASE-3899
> URL: https://issues.apache.org/jira/browse/HBASE-3899
> Project: HBase
> Issue Type: Improvement
> Components: ipc
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Fix For: 0.92.0
>
> Attachments: HBASE-3899-2.patch, HBASE-3899.patch, asyncRpc.txt,
> asyncRpc.txt
>
>
> In the current implementation, the server handler thread picks up an item
> from the incoming callqueue, processes it and then wraps the response as a
> Writable and sends it back to the IPC server module. This wastes
> thread-resources when the thread is blocked for disk IO (transaction logging,
> read into block cache, etc).
> It would be nice if we can make the RPC Server Handler threads pick up a call
> from the IPC queue, hand it over to the application (e.g. HRegion), the
> application can queue it to be processed asynchronously and send a response
> back to the IPC server module saying that the response is not ready. The RPC
> Server Handler thread is now ready to pick up another request from the
> incoming callqueue. When the queued call is processed by the application, it
> indicates to the IPC module that the response is now ready to be sent back to
> the client.
> The RPC client continues to experience the same behaviour as before. A RPC
> client is synchronous and blocks till the response arrives.
> This RPC enhancement allows us to do very powerful things with the
> RegionServer. In future, we can make enhance the RegionServer's threading
> model to a message-passing model for better performance. We will not be
> limited by the number of threads in the RegionServer.
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