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https://issues.apache.org/jira/browse/HBASE-2957?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12906645#action_12906645
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ryan rawson commented on HBASE-2957:
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why dont you shard your counters?  With the perf optimizations we did
last friday, you should easily be able to support 100m counters/day
per row, just shard row-wise and you are set for scaling.

-ryan




> 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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