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https://issues.apache.org/jira/browse/HBASE-17852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16273955#comment-16273955
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Vladimir Rodionov commented on HBASE-17852:
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{quote}
There were concerns above on cross RS rpc to write the paths, I was trying to 
think of easiest way of avoiding that. How about returning the map as part of 
response here and then issue rpc to master from client side. It's easy and 
safer to retry from client side if remote resource isn't available.
I'd suggest going extra step, an easy one though - collect all paths on client 
side and do single put request. That'll give two benefits:
Will make it transactional incremental backup
If put fails repeatedly, you can either fail bulk load altogether, or throw 
error to user telling that these bulk loaded files failed to backup and that 
only full backup will include them.
{quote}

I will think about this and will get back to you, [~appy] shortly. Thanks, for 
suggestion.

> Add Fault tolerance to HBASE-14417 (Support bulk loaded files in incremental 
> backup)
> ------------------------------------------------------------------------------------
>
>                 Key: HBASE-17852
>                 URL: https://issues.apache.org/jira/browse/HBASE-17852
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Vladimir Rodionov
>            Assignee: Vladimir Rodionov
>             Fix For: 2.0.0
>
>         Attachments: HBASE-17852-v1.patch, HBASE-17852-v2.patch, 
> HBASE-17852-v3.patch, HBASE-17852-v4.patch, HBASE-17852-v5.patch, 
> HBASE-17852-v6.patch, HBASE-17852-v7.patch, HBASE-17852-v8.patch, 
> HBASE-17852-v9.patch
>
>
> Design approach rollback-via-snapshot implemented in this ticket:
> # Before backup create/delete/merge starts we take a snapshot of the backup 
> meta-table (backup system table). This procedure is lightweight because meta 
> table is small, usually should fit a single region.
> # When operation fails on a server side, we handle this failure by cleaning 
> up partial data in backup destination, followed by restoring backup 
> meta-table from a snapshot. 
> # When operation fails on a client side (abnormal termination, for example), 
> next time user will try create/merge/delete he(she) will see error message, 
> that system is in inconsistent state and repair is required, he(she) will 
> need to run backup repair tool.
> # To avoid multiple writers to the backup system table (backup client and 
> BackupObserver's) we introduce small table ONLY to keep listing of bulk 
> loaded files. All backup observers will work only with this new tables. The 
> reason: in case of a failure during backup create/delete/merge/restore, when 
> system performs automatic rollback, some data written by backup observers 
> during failed operation may be lost. This is what we try to avoid.
> # Second table keeps only bulk load related references. We do not care about 
> consistency of this table, because bulk load is idempotent operation and can 
> be repeated after failure. Partially written data in second table does not 
> affect on BackupHFileCleaner plugin, because this data (list of bulk loaded 
> files) correspond to a files which have not been loaded yet successfully and, 
> hence - are not visible to the system 



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