Change default checksum type to CRC32C

[symious]

Changing the default checksum type to CRC32.

We have some users using uploading files which has the checksum type of "CRC32", but the default type is "CRC32C" since the very begining.

This will cause a checksum mismatch issue when users are using distcp to copy the files. Although we can work around this issue on HDFS side by adding "-pc" to the distcp command, we think it's also good to change the default value from GO side.

[symious]

@colinmarc Could you help to review the PR?

[colinmarc]

Hi @symious,

The default checksum per the source is CRC32: https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs-client/src/main/proto/hdfs.proto#L530

I'm not inclined to change it here (the protos have always been a straight copy from the source), but maybe I'm missing something? I'll close this for now, but please feel free to make the argument!

[symious]

@colinmarc Thank you for the reply.

The default value Clients are using should be here: https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/client/HdfsClientConfigKeys.java#L133

And CRC32C has been more efficient than the CRC32.

[colinmarc]

Huh, okay, thanks for clarifying that. I merged this in 325f0cf.

[symious]

@colinmarc Thank you for the change.