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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-3875) Issue handling checksum errors in write pipeline
Date Sat, 01 Dec 2012 02:35:58 GMT

     [ https://issues.apache.org/jira/browse/HDFS-3875?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Kihwal Lee updated HDFS-3875:
-----------------------------

    Attachment: hdfs-3875.trunk.with.test.patch.txt
                hdfs-3875.trunk.no.test.patch.txt

Two new patches for trunk are attached. The two has the identical implementation of the bug
fix. One includes a test case and necessary changes to make the test work.  Since the test
is a bit invasive, the no test version is also attached.

The test simulates corruption during data transmission. It demonstrates the effectiveness
of patch. Without the patch, corruption is detected much later after the data is written and
acked, which makes recovery impossible.

The patch for branch-0.23 requires a slightly different patch.
                
> 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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