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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7965) Port table locking to 0.94 (HBASE-7305, HBASE-7546, HBASE-7933)
Date Sat, 02 Mar 2013 00:43:13 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13591154#comment-13591154

Enis Soztutar commented on HBASE-7965:

Valid concerns. Let me try to address some of the these.
bq. Adding locks prevents races, but could enable deadlocks. We've lived with these races
for a long time (at least since 0.90) and basically understand them. This is a fundamentally
different failure scenario and has me worried.
At this stage, there is no hbck support for fixing a table lock, but if deadlock happens,
the user can just delete the lock znodes. Plus, I am proposing to backport this as disabled
by default. All the lock operations are no-op if disabled, no critical code path will be affected
by default. If needed, we can say that this feature is experimental in 0.94. 
bq. This is going to affect a vital path (can't use hbase if you can't create tables). I'd
honestly like some evidence (a story!) about some long running tests with fault injection
using this mechanism. This will go a long way to allaying my concerns.
I think I've went to some details of how I did test these in HBASE-7305 and HBASE-7546 and
the RB for those. I'll consolidate the testing effort here. 
bq. What is the rolling upgrade story (0.94.5 -> 0.94.7). Does cause any incompatibilities?
The set of patches has nothing to do with the wire protocol. I don't see your concern here.

> Port table locking to 0.94 (HBASE-7305, HBASE-7546, HBASE-7933)
> ---------------------------------------------------------------
>                 Key: HBASE-7965
>                 URL: https://issues.apache.org/jira/browse/HBASE-7965
>             Project: HBase
>          Issue Type: New Feature
>          Components: master, Zookeeper
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 0.94.7
> Port table locking to 0.94 (HBASE-7305, HBASE-7546, HBASE-7933). This is a new feature,
but there has been some interest, and it is necessary for snapshots, and online merge, which
are also candidates for backport. 
> If we port snapshots, we might need HBASE-7848 as well.
> We can also do disabled by default.

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