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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-3588) Proposal to optimize ReadWriteConsistencyControl
Date Wed, 02 Mar 2011 19:41:37 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3588?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13001575#comment-13001575

dhruba borthakur commented on HBASE-3588:

I am yet to measure (at scale) the performance improvement. But does the code look good and

The difference is not just one memstore update. Especially if we have lots of regionserver
threads, there are many threads inserting into memstore in parallel.

> Proposal to optimize ReadWriteConsistencyControl
> ------------------------------------------------
>                 Key: HBASE-3588
>                 URL: https://issues.apache.org/jira/browse/HBASE-3588
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: rwcc.trunk.1, rwcc.trunk.1
> The ReadWriteConsistencyControl (RWCC) mechanism facilitates making a set of memstore
updates atomically visible to readers. Also, the rwcc.completeMemstoreInsert() blocks till
the memstore read point advances to the current writeNumber. This is done to ensure that if
an application that does a put immediately issues a new get call for the same key, then the
get should see the values inserted by the previous call to put. The current implementation
assumes this worst-case and penalizes the put rpc to not return to the client until the read
point advances to this transaction's write number.
> In many use-cases, the application never actually issues a get for the most recent put
that it inserted. In this case, it would be nice if we can transfer the penalty (of blocking)
to the get call that follows the initial put.

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