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https://issues.apache.org/jira/browse/HDFS-17267?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17791659#comment-17791659
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farmmamba edited comment on HDFS-17267 at 11/30/23 2:43 PM:
------------------------------------------------------------
We can debug the unit test method testPipelineRecoveryWithSlowNode to verify
this PR.
Set breakpoint in DataStreamer#run : `LOG.debug("{} sending {}", this, one);`.
We can see the DFSPacket with seq=3 sends twice.
BTW, on datanode side. It will not write packet data twice, because if will
compare the onDiskLen and offsetInBlock in method receivePacket(). if onDiskLen
>= offsetInBlock, there will not happen writing data behavior.
was (Author: zhanghaobo):
We can debug the unit test method testPipelineRecoveryWithSlowNode to verify
this PR.
Set breakpoint in DataStreamer#run : `LOG.debug("{} sending {}", this, one);`.
We can see the DFSPacket with seq=3 sends twice.
> Client send the smae packet multiple times when method markSlowNode throws
> IOException.
> ---------------------------------------------------------------------------------------
>
> Key: HDFS-17267
> URL: https://issues.apache.org/jira/browse/HDFS-17267
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 3.3.6
> Reporter: farmmamba
> Assignee: farmmamba
> Priority: Major
>
> Since we have HDFS-16348, we can kick out SLOW node in pipeline when writing
> data to pipeline.
> And I think it introduced a problem, that is the same packet will be sent
> twice or more times when we kick out SLOW node.
>
> The flow are as below:
> 1、 DFSPacket p1 is pushed into dataQueue.
> 2、DataStreamer takes DFSPacket p1 from dataQueue.
> 3、Remove p1 from dataQueue and push p1 into ackQueue.
> 4、sendPacket(p1).
> 5、In ResponseProcessor#run, read pipelineAck for p1.
> 6、We meet SlOW node, so method markSlowNode throw IOException and does not
> execute `ackQueue.removeFirst();`.
> 7、In next loop of DataStreamer#run, we come into method
> processDatanodeOrExternalError and execute `dataQueue.addAll(0, ackQueue);`.
> 8、the p1 will be sent repeatedly.
>
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