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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 Mon, 17 Dec 2012 23:06:14 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13534398#comment-13534398
] 

Jimmy Xiang commented on HBASE-6423:
------------------------------------

@binlijin, yes, it is safe to use the old style for this one. Can you file a jira and post
a patch? Thanks.
                
> 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
>             Fix For: 0.96.0, 0.94.4
>
>         Attachments: 0.94-6423.patch, 0.94-6423_v4.patch, 6423.addendum, trunk-6423.patch,
trunk-6423_v2.1.patch, trunk-6423_v2.patch, trunk-6423_v3.2.patch, trunk-6423_v3.3.patch,
trunk-6423_v3.4.patch, trunk-6423_v4.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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