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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-4403) DFSClient can infer checksum type when not provided by reading first byte
Date Wed, 16 Jan 2013 22:56:14 GMT

     [ https://issues.apache.org/jira/browse/HDFS-4403?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon updated HDFS-4403:
------------------------------

    Attachment: hdfs-4403.txt

Attached patch fixes the javadoc and adds the 'final' keyword per Colin's review.

I didn't change the buffer sizes, since that's an issue in lots and lots of places in the
DFS source. We should change it throughout rather than try to change it in this unrelated
JIRA.
                
> DFSClient can infer checksum type when not provided by reading first byte
> -------------------------------------------------------------------------
>
>                 Key: HDFS-4403
>                 URL: https://issues.apache.org/jira/browse/HDFS-4403
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client
>    Affects Versions: 2.0.2-alpha
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Minor
>         Attachments: hdfs-4403.txt, hdfs-4403.txt
>
>
> HDFS-3177 added the checksum type to OpBlockChecksumResponseProto, but the new protobuf
field is optional, with a default of CRC32. This means that this API, when used against an
older cluster (like earlier 0.23 releases) will falsely return CRC32 even if that cluster
has written files with CRC32C. This can cause issues for distcp, for example.
> Instead of defaulting the protobuf field to CRC32, we can leave it with no default, and
if the OpBlockChecksumResponseProto has no checksum type set, the client can send OP_READ_BLOCK
to read the first byte of the block, then grab the checksum type out of that response (which
has always been present)

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