[jira] [Resolved] (PHOENIX-3326) Restoring SYSTEM.CATALOG from snapshot causes clients to run into UpgradeInProgressException

["Samarth Jain (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/PHOENIX-3326?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Samarth Jain resolved PHOENIX-3326.
-----------------------------------
       Resolution: Fixed
    Fix Version/s:     (was: 4.8.2)
                       (was: 4.10.0)
                   4.9.0

> Restoring SYSTEM.CATALOG from snapshot causes clients to run into UpgradeInProgressException
> --------------------------------------------------------------------------------------------
>
>                 Key: PHOENIX-3326
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-3326
>             Project: Phoenix
>          Issue Type: Bug
>    Affects Versions: 4.8.1
>            Reporter: Samarth Jain
>            Assignee: Samarth Jain
>             Fix For: 4.9.0
>
>         Attachments: PHOENIX-3326_4.8-HBase-0.98.patch, PHOENIX-3326_4.8-HBase-0.98_v2.patch, PHOENIX-3326_wip.patch
>
>
> We create a snapshot of the SYSTEM.CATALOG table only after the client is able to successfully acquire a distributed mutex of sorts. This means the snapshot also ends up containing the row that serves as the mutex. Now when restoring the table from snapshot, this rows is still present which causes clients to throw UpgradeInProgress exception. 
> I can think of a couple of ways to fix this:
> 1) Do the checkAndPut for the UPGRADE_MUTEX after creating the snapshot. I am not too sure though how about HBase handles concurrent snapshot requests. Do clients get an exception? Also we potentially could end up creating more snapshots than we really need to. 
> 2) Do the checkAndPut for the UPGRADE_MUTEX in a different table (possibly SYSTEM.SEQUENCE). This way the restored snapshot won't have the row. We would need to delete the row from SYSTEM.SEQUENCE after the upgrade is done (successfully or unsuccessfully).
> [~jamestaylor] - WDYT? 
> FYI, [~lhofhansl] - this is probably a blocker for 4.8.1



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