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From "Jimmy Xiang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6423) Writes should not block reads on blocking updates to memstores
Date Wed, 21 Nov 2012 01:44:59 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13501646#comment-13501646

Jimmy Xiang commented on HBASE-6423:

@Stack, I addressed couple of your comments and put the patch on RB: https://reviews.apache.org/r/8149/.
It will make the review easier.

This patch will make sure it is possible that we don't wait for the lock forever, so that
the IPC handler is released if the region is busy.  Therefore, other none-busy regions can
be accessed.  That's how we address Karthik's original comment in the issue.

Sure, we can backport, once we are ready to integrate it into the trunk branch.
> Writes should not block reads on blocking updates to memstores
> --------------------------------------------------------------
>                 Key: HBASE-6423
>                 URL: https://issues.apache.org/jira/browse/HBASE-6423
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Karthik Ranganathan
>            Assignee: Jimmy Xiang
>         Attachments: trunk-6423.patch, trunk-6423_v2.1.patch, trunk-6423_v2.patch
> We have a big data use case where we turn off WAL and have a ton of reads and writes.
We found that:
> 1. flushing a memstore takes a while (GZIP compression)
> 2. incoming writes cause the new memstore to grow in an unbounded fashion
> 3. this triggers blocking memstore updates
> 4. in turn, this causes all the RPC handler threads to block on writes to that memstore
> 5. we are not able to read during this time as RPC handlers are blocked
> At a higher level, we should not hold up the RPC threads while blocking updates, and
we should build in some sort of rate control.

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