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https://issues.apache.org/jira/browse/HADOOP-10295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13883865#comment-13883865
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Laurent Goujon commented on HADOOP-10295:
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{quote}
I personally like your idea in HADOOP-10297. That can simplify the logic there.
However, FileChecksum is a public API marked as stable, to add a new abstract
method there may cause incompatibility (e.g., other ppl may have implemented
their own FileChecksum). A workaround here can be adding getChecksumOpt() to
FileChecksum and let it return null.
{quote}
Yes, my patch for HADOOP-10297 breaks source compatibility (but not binary
compatibility). It may be okay for next Hadoop major version, but probably not
for a minor version. Waiting for some guidance here (and it's really easy to
change)
{quote}
I thought about this problem. To me checksum type may be a little bit different
from other file attributes, since other file attributes are all metadata stored
in NN. Thus in my first patch I just add a new option. But now I think to put
the checksum type in the FileAttribute enum should be more clear.
{quote}
>From the user point of view, block size, replication and checksum option are
>seen as the same kind of metadata. Only from the FileSystem API, it is seen as
>different kind of metadata because the information is not stored in the same
>place.
{quote}
Currently I have a 001 patch which fixes the CreateFlag bug and adds a unit
test. My original plan is to post it after I finish system test in my local
cluster. But since you've worked on this issue for some time and already have a
decent patch, I'd like to review your patch and commit it when it is ready.
{quote}
My patch is mostly ready I think, but it is blocked by the other tickets I
mentioned. Hopefully they will be reviewed quickly.
> Allow distcp to automatically identify the checksum type of source files and
> use it for the target
> --------------------------------------------------------------------------------------------------
>
> Key: HADOOP-10295
> URL: https://issues.apache.org/jira/browse/HADOOP-10295
> Project: Hadoop Common
> Issue Type: Improvement
> Affects Versions: 2.2.0
> Reporter: Jing Zhao
> Assignee: Jing Zhao
> Attachments: HADOOP-10295.000.patch, hadoop-10295.patch
>
>
> Currently while doing distcp, users can use "-Ddfs.checksum.type" to specify
> the checksum type in the target FS. This works fine if all the source files
> are using the same checksum type. If files in the source cluster have mixed
> types of checksum, users have to either use "-skipcrccheck" or have checksum
> mismatching exception. Thus we may need to consider adding a new option to
> distcp so that it can automatically identify the original checksum type of
> each source file and use the same checksum type in the target FS.
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