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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8446) Allow parallel snapshot of different tables
Date Wed, 01 May 2013 23:10:16 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8446?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13647049#comment-13647049
] 

Sergey Shelukhin commented on HBASE-8446:
-----------------------------------------

Sorry, yeah, thread count has nothing to do with this (just the unclear comment).

takeSnapshot is called from snapshot RPC. Suppose two RPCs arrive at the same time for the
same table.
There are no checks in takeSnapshot that will make one "win", so both go on to prepareToTakeSnapshot.
First enters synchronized prepareToTakeSnapshot, does both checks, they are ok - it only does
get-s on the map. It exits it.
Second enters prepareToTakeSnapshot, does both checks, they are ok similarly, so it proceeds.
Then both, in order, call snapshotEnabledTable which calls snapshotTable, we are synchronized
again.
First guy submits the handler and puts, so does the 2nd guy.

Am I missung something?

                
> Allow parallel snapshot of different tables
> -------------------------------------------
>
>                 Key: HBASE-8446
>                 URL: https://issues.apache.org/jira/browse/HBASE-8446
>             Project: HBase
>          Issue Type: Improvement
>          Components: snapshots
>    Affects Versions: 0.95.0
>            Reporter: Matteo Bertozzi
>            Assignee: Matteo Bertozzi
>            Priority: Minor
>             Fix For: 0.95.2
>
>         Attachments: HBASE-8446-94.patch, HBASE-8446-v0.patch, HBASE-8446-v1.patch, HBASE-8446-v2.patch,
HBASE-8446-v3.patch, HBASE-8446-v4.patch, HBASE-8446-v5.patch
>
>
> currently only one snapshot at the time is allowed.
> Like for the restore, we should allow taking snapshot of different tables in parallel.

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