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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2957) Release row lock when waiting for wal-sync
Date Tue, 07 Sep 2010 00:07:33 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2957?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12906625#action_12906625
] 

Jonathan Gray commented on HBASE-2957:
--------------------------------------

I think Prakash and Dhruba are specifically thinking about ICVs rather than Puts.  The begin
insert / complete insert stuff doesn't actually get used at all for ICVs, in this case the
memstoreTS=0.  So there is no "complete memstore insert".

Maybe the special ICV group commit makes sense.  Otherwise we'll have to relax some constraints
or change how ICV works.

> Release row lock when waiting for wal-sync
> ------------------------------------------
>
>                 Key: HBASE-2957
>                 URL: https://issues.apache.org/jira/browse/HBASE-2957
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver, wal
>    Affects Versions: 0.20.0
>            Reporter: Prakash Khemani
>
> Is there a reason to hold on to the row-lock while waiting for the WAL-sync to be completed
by the logSyncer thread?
> I think data consistency will be guaranteed even if the following happens (a) the row
lock is held while the row is updated in memory (b) the row lock is released after queuing
the KV record for WAL-syncing (c) the log-sync system guarantees that the log records for
any given row are synced in order (d) the HBase client only receives a success notification
after the sync completes (no change from the current state)
> I think this should be a huge win. For my use case, and I am sure for others,  the handler
thread spends the bulk of its row-lock critical section  time waiting for sync to complete.
> Even if the log-sync system cannot guarantee the orderly completion of sync records,
the "Don't hold row lock while waiting for sync" option should be available to HBase clients
on a per request basis.

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