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https://issues.apache.org/jira/browse/HBASE-3588?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13001606#comment-13001606
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ryan rawson commented on HBASE-3588:
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I had a few questions... This patch doesnt seem to remove the wait for the
memstoreRead point to catch up to the just-completed write... Do you see that
as well?
Also it seems like every reader is going to have to do this sequence:
- get the most recent written value
- wait until it becomes readable
Does that seem right? Every reader will have a little delay (on a busy region
of course) between when it starts and when it can start pulling data down.
One use case to worry about is a Row put followed by a CheckAndPut to the same
row. I think this patch looks like it respects that use case, can you verify?
> 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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