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From "Jianwei Cui (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15433) SnapshotManager#restoreSnapshot not update table and region count quota correctly when encountering exception
Date Mon, 14 Mar 2016 11:52:33 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15433?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15193148#comment-15193148
] 

Jianwei Cui commented on HBASE-15433:
-------------------------------------

The table must be disabled during restoreSnapshot, so that the {{tableRegionCount}} won't
change. Assume there won't be concurrent restoreSnapshot requests for the same table, the
{{checkAndUpdateNamespaceRegionQuota}} after {{restoreSnapshot}} will be executed only when
{{tableRegionCount > snapshotRegionCount}} satisfied, this means we have preserved enough
region count for the {{checkAndUpdateNamespaceRegionQuota}} from the namespace quota. Therefore,
other thread operations won't make the {{checkAndUpdateNamespaceRegionQuota}} fail if they
operating on different tables? However, if there are concurrent restoreSnapshot requests for
the same table, it will cause problem, and we may need lock to make sure the quota information
is updated correctly, or we can move the quota check and update logic in the {{RestoreSnapshotHandler}}
after table lock is held?

> SnapshotManager#restoreSnapshot not update table and region count quota correctly when
encountering exception
> -------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-15433
>                 URL: https://issues.apache.org/jira/browse/HBASE-15433
>             Project: HBase
>          Issue Type: Bug
>          Components: snapshots
>    Affects Versions: 2.0.0
>            Reporter: Jianwei Cui
>         Attachments: HBASE-15433-trunk-v1.patch, HBASE-15433-trunk-v2.patch, HBASE-15433-trunk.patch
>
>
> In SnapshotManager#restoreSnapshot, the table and region quota will be checked and updated
as:
> {code}
>       try {
>         // Table already exist. Check and update the region quota for this table namespace
>         checkAndUpdateNamespaceRegionQuota(manifest, tableName);
>         restoreSnapshot(snapshot, snapshotTableDesc);
>       } catch (IOException e) {
>         this.master.getMasterQuotaManager().removeTableFromNamespaceQuota(tableName);
>         LOG.error("Exception occurred while restoring the snapshot " + snapshot.getName()
>             + " as table " + tableName.getNameAsString(), e);
>         throw e;
>       }
> {code}
> The 'checkAndUpdateNamespaceRegionQuota' will fail if regions in the snapshot make the
region count quota exceeded, then, the table will be removed in the 'catch' block. This will
make the current table count and region count decrease, following table creation or region
split will succeed even if the actual quota is exceeded.



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