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Posted to hdfs-dev@hadoop.apache.org by "Todd Lipcon (JIRA)" <ji...@apache.org> on 2013/01/15 02:13:11 UTC

[jira] [Created] (HDFS-4403) DFSClient can infer checksum type when not provided by reading first byte

Todd Lipcon created HDFS-4403:
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             Summary: 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


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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