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https://issues.apache.org/jira/browse/HDFS-3875?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13507845#comment-13507845
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Kihwal Lee commented on HDFS-3875:
----------------------------------
I originally changed PipelineACK to return errors instead of making writer
terminate. It generally worked, but some corner cases required a significant
change in DFSOutputStream. So I decided to simplify and make it not send
ACK-back on checksum errors and terminate as it would in case of any other
error. Local AckStatus is saved in each status tracking packet(not actual data
packet), so that successful acks enqueued before checksum error still can be
sent.
> Issue handling checksum errors in write pipeline
> ------------------------------------------------
>
> Key: HDFS-3875
> URL: https://issues.apache.org/jira/browse/HDFS-3875
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode, hdfs-client
> Affects Versions: 2.0.2-alpha
> Reporter: Todd Lipcon
> Assignee: Kihwal Lee
> Priority: Blocker
> Attachments: hdfs-3875.trunk.no.test.patch.txt,
> hdfs-3875.trunk.with.test.patch.txt, hdfs-3875-wip.patch
>
>
> We saw this issue with one block in a large test cluster. The client is
> storing the data with replication level 2, and we saw the following:
> - the second node in the pipeline detects a checksum error on the data it
> received from the first node. We don't know if the client sent a bad
> checksum, or if it got corrupted between node 1 and node 2 in the pipeline.
> - this caused the second node to get kicked out of the pipeline, since it
> threw an exception. The pipeline started up again with only one replica (the
> first node in the pipeline)
> - this replica was later determined to be corrupt by the block scanner, and
> unrecoverable since it is the only replica
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