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https://issues.apache.org/jira/browse/HDFS-10314?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15510391#comment-15510391
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Yongjun Zhang edited comment on HDFS-10314 at 9/21/16 4:11 PM:
---------------------------------------------------------------
Hi [~jingzhao],
For clarity, and as a recap, here is a comparison table between -diff and the
proposed -rdiff, which shows the symmetricity:
||Comparison||-diff s1 s2 <src> <tgt>||-rdiff s2 s1 <src> <tgt>||
|Current feature state|Existing in distcp|Proposed Addition |
|Functionality| Given <tgt>'s current state is s1, make <tgt>'s current state
the same as newer snapshot s2 | Given <tgt>'s current state is s2, make <tgt>'s
current state the same as older snapshot s1 |
|Requirements| # <src> and <tgt> need to be different paths
# both <src> and <tgt> have snapshot s1 with exact same content
# <src> has snapshot s2
# s2 is newer than s1
# <tgt>'s current state is the same as s1
# <tgt> doesn't have snapshot s2 | # <src> and <tgt> can be the same or
different paths
# both <src> and <tgt> have snapshot s1 with exact same content
# <tgt> has snapshot s2
# s2 is newer than s1
# <tgt>'s current state is the same as s2
# <src> may or may not have snapshot s2 |
|Steps|# calculate snapshotDiff<s1,s2> at <src>
# apply rename/delete part of snapshotDiff on <tgt>
# copy modified part of snapshotDiff from s2 of <src> to <tgt> | # calculate
snapshotDiff<s2,s1> at <tgt>
# apply rename/delete part of snapshotDiff on <tgt>
# copy modified part of snapshotDiff from s1 of <src> to <tgt> |
The original thinking was to add -ridff to distcp (solution A), but because of
the concern of confusing semantics, it's suggested to introduce a new command
here (solution B).
Thanks.
was (Author: yzhangal):
Hi [~jingzhao],
For clarity, and as a recap, here is a comparison table between -diff and the
proposed -rdiff, which shows the symmetricity:
||Comparison||-diff s1 s2 <src> <tgt>||-rdiff s2 s1 <src> <tgt>||
|Current feature state|Existing in distcp|Proposed Addition |
|Functionality| Given <tgt>'s current state is s1, make <tgt>'s current state
the same as newer snapshot s2 | Given <tgt>'s current state is s2, make <tgt>'s
current state the same as older snapshot s1 |
|Requirements| # <src> and <tgt> need to be different paths
# both <src> and <tgt> have snapshot s1 with exact same content
# <src> has snapshot s2
# s2 is newer than s1
# <tgt>'s current state is the same as s1
# <tgt> doesn't have snapshot s2 | # <src> and <tgt> can be the same or
different paths
# both <src> and <tgt> have snapshot s1 with exact same content
# <tgt> has snapshot s2
# s2 is newer than s1
# <tgt>'s current state is the same as s2
# <src> may or may not have snapshot s2 |
|Steps|# calculate snapshotDiff<s1,s2> at <src>
# apply rename/delete part of snapshotDiff on <tgt>
# copy modified part of snapshotDiff from s1 of <src> to <tgt> | # calculate
snapshotDiff<s2,s1> at <tgt>
# apply rename/delete part of snapshotDiff on <tgt>
# copy modified part of snapshotDiff from s1 of <src> to <tgt> |
The original thinking was to add -ridff to distcp (solution A), but because of
the concern of confusing semantics, it's suggested to introduce a new command
here (solution B).
Thanks.
> A new tool to sync current HDFS view to specified snapshot
> ----------------------------------------------------------
>
> Key: HDFS-10314
> URL: https://issues.apache.org/jira/browse/HDFS-10314
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: tools
> Reporter: Yongjun Zhang
> Assignee: Yongjun Zhang
> Attachments: HDFS-10314.001.patch
>
>
> HDFS-9820 proposed adding -rdiff switch to distcp, as a reversed operation of
> -diff switch.
> Upon discussion with [~jingzhao], we will introduce a new tool that wraps
> around distcp to achieve the same purpose.
> I'm thinking about calling the new tool "rsync", similar to unix/linux
> command "rsync". The "r" here means remote.
> The syntax that simulate -rdiff behavior proposed in HDFS-9820 is
> {code}
> rsync <fromSnapshotName> <toSnapshotName> <source> <target>
> {code}
> This command ensure <fromSnapshotName> is newer than <toSnapshotName>.
> I think, In the future, we can add another command to have the functionality
> of -diff switch of distcp.
> {code}
> sync <fromSnapshotName> <toSnapshotName> <source> <target>
> {code}
> that ensures <fromSnapshotName> is older than <toSnapshotName>.
> Thanks [~jingzhao].
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