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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17852) Add Fault tolerance to HBASE-14417 (Support bulk loaded files in incremental backup)
Date Wed, 06 Dec 2017 17:13:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16280521#comment-16280521
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Josh Elser commented on HBASE-17852:
------------------------------------

bq. Yea, retry would be good. File a JIRA?

HBASE-19441. Tagged in the "Phase 4" umbrella.

{quote}
So, I'd say, there are many things implicitly broken with current design.

Strong -1 on shipping it unless they are fixed.
{quote}

[~appy], while I appreciate the keen eye you're applying here, how can we move forward here?
I know it's very frustrating for Vlad to have something that he's already built+tested be
taken back to the drawing board abruptly. Do you truly feel like this feature is harmful as
compared to what the current implementation is?

I'd prefer to see this land in master, then we take the concept back to the drawing board
and, with all of your help, we revisit this and come up with a design and implementation that
works for concurrent backup sessions (as Vlad has this on the Phase4 roadmap already).

> 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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