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https://issues.apache.org/jira/browse/HDFS-9494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15055552#comment-15055552
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GAO Rui commented on HDFS-9494:
-------------------------------
Thank you very much [~szetszwo]. I have refactored the code and using
{{ExecutorCompletionService.take()}} to waiting for all the streamer flushing.
Because, {{ExecutorCompletionService}} could not tell us how many Future
objects are still there waiting, so I use {{healthyStreamerCount}} to count how
many times we should call take(). And {{Runnable.run()}} can not throw
Exception, so I use {{Callable.call() throws Exception}} and return null.
> Parallel optimization of DFSStripedOutputStream#flushAllInternals( )
> --------------------------------------------------------------------
>
> Key: HDFS-9494
> URL: https://issues.apache.org/jira/browse/HDFS-9494
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: GAO Rui
> Assignee: GAO Rui
> Priority: Minor
> Attachments: HDFS-9494-origin-trunk.00.patch,
> HDFS-9494-origin-trunk.01.patch
>
>
> Currently, in DFSStripedOutputStream#flushAllInternals( ), we trigger and
> wait for flushInternal( ) in sequence. So the runtime flow is like:
> {code}
> Streamer0#flushInternal( )
> Streamer0#waitForAckedSeqno( )
> Streamer1#flushInternal( )
> Streamer1#waitForAckedSeqno( )
> …
> Streamer8#flushInternal( )
> Streamer8#waitForAckedSeqno( )
> {code}
> It could be better to trigger all the streamers to flushInternal( ) and
> wait for all of them to return from waitForAckedSeqno( ), and then
> flushAllInternals( ) returns.
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