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From "Mike Drob (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17852) Add Fault tolerance to HBASE-14417 (Support bulk loaded files in incremental backup)
Date Thu, 30 Nov 2017 22:11:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16273568#comment-16273568
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Mike Drob commented on HBASE-17852:
-----------------------------------

Thank you for pointing at the parent ticket, I missed that there was design doc in there.

I'm worried about our current design choices for future concurrent backup design. Please correct
my gaps in understanding here:

Current approach, which is limited to single backup operation involves snapshot the backup
state table (what you refer to as backup system table, but I think state is more appropriate
term) and then if failure then we restore the state? In future are we going to have multiple
tables in backup namespace for each table to be backed up so that we can have concurrent approaches?
Otherwise the concurrent backup solution will be a complete rewrite I expect.

Do backup operations have timeouts? I don't see them in the code, but could be looking at
the wrong place.

> 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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