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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3875) Issue handling checksum errors in write pipeline
Date Fri, 17 May 2013 23:51:16 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3875?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13661161#comment-13661161
] 

Suresh Srinivas commented on HDFS-3875:
---------------------------------------

[~kihwal] the new solutions looks much better. Nice work!

Some minor comments. +1 with those addressed:
# DFSOutputStream.java
#* Initialize lastAckedSeqnoBeforeFailure to appropriate value. lastAckedSeqNo is initialized
to -1.
#* Change info log, print warn? Instead of "Already tried 5 times" -> "Already retried
5 times", given total attempts are 6 and retries are 5.
# DFSClientFaultInjecto#uncorruptPacket() - does it need to throw IOException?

                
> 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: Critical
>         Attachments: hdfs-3875.branch-0.23.no.test.patch.txt, hdfs-3875.branch-0.23.patch.txt,
hdfs-3875.branch-0.23.with.test.patch.txt, hdfs-3875.patch.txt, hdfs-3875.trunk.no.test.patch.txt,
hdfs-3875.trunk.no.test.patch.txt, hdfs-3875.trunk.patch.txt, hdfs-3875.trunk.patch.txt, hdfs-3875.trunk.with.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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