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https://issues.apache.org/jira/browse/PHOENIX-3326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15521581#comment-15521581
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Lars Hofhansl commented on PHOENIX-3326:
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I assumed ZK might be undesirable (complex, another service to rely upon, etc).
Some recipes are here:
https://zookeeper.apache.org/doc/trunk/recipes.html#sc_recipes_Locks, but I'd
recommend Curator (http://curator.apache.org/)
[~sukumaddineni] has done locking for our backups solutions.
[~jamestaylor], my thinking was that if we expire the lock after a reasonable
time, it'd be OK to leave it on SYSTEM.CATALOG.
Let's not have another table and a big change 4.8 release, I'd rather roll a
new RC *without* the Snapshot feature.
> 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
> Reporter: Samarth Jain
> Assignee: Samarth Jain
> 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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