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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3875) Issue handling checksum errors in write pipeline
Date Sun, 02 Dec 2012 03:58:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3875?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13508138#comment-13508138
] 

Kihwal Lee commented on HDFS-3875:
----------------------------------

Also, checksumError is set true before returning, so receiveBlock() will actually end up throwing
an exception. I experimented with receiveBlock() throwing an exception and also simply returning
and they all worked fine. I thought you were refering to this. 

To answer your question better, the occurance checksum error is already logged and the exception
thrown in receiveBlock() will clearly show what happened. We could catch IOexception in receiveBlock(),
check checksumError and rethrow. 
                
> 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.branch-0.23.no.test.patch.txt, hdfs-3875.branch-0.23.with.test.patch.txt,
hdfs-3875.trunk.no.test.patch.txt, hdfs-3875.trunk.no.test.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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