[
https://issues.apache.org/jira/browse/HBASE-5547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13257114#comment-13257114
]
Lars Hofhansl commented on HBASE-5547:
--------------------------------------
What I had in mind when I filed this was something quite simple: A single znode
that all RegionServers would check when deleting any HFile and then based on
existence or value of that znode either delete the HFile or rename it. Of
things are never quite as simple...
To get a guaranteed consistent snapshot the RegionServers need to check for the
znode's value synchronously in the delete path (or at least I see no other
way). Otherwise there are times when the RegionServers do not agree and some
files will be deleted and some will be backed up with no possibility for the
client to know exactly as of when the backup would be consistent.
Since HFiles are deleted as result of a compaction in an asynchronous thread,
synchronously checking the znode should not cause performance issues, unless we
fear we'll overload ZK.
This simple solution would add special code for just this scenario, which is
bad. At the same time it would be relatively simple (famous last words), so
that's something to weigh.
> Don't delete HFiles when in "backup mode"
> -----------------------------------------
>
> Key: HBASE-5547
> URL: https://issues.apache.org/jira/browse/HBASE-5547
> Project: HBase
> Issue Type: New Feature
> Reporter: Lars Hofhansl
> Assignee: Jesse Yates
>
> This came up in a discussion I had with Stack.
> It would be nice if HBase could be notified that a backup is in progress (via
> a znode for example) and in that case either:
> 1. rename HFiles to be delete to <file>.bck
> 2. rename the HFiles into a special directory
> 3. rename them to a general trash directory (which would not need to be tied
> to backup mode).
> That way it should be able to get a consistent backup based on HFiles (HDFS
> snapshots or hard links would be better options here, but we do not have
> those).
> #1 makes cleanup a bit harder.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
