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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6423) Writes should not block reads on blocking updates to memstores
Date Sun, 18 Nov 2012 18:32:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13499867#comment-13499867
] 

Ted Yu commented on HBASE-6423:
-------------------------------

Patch looks good.
{code}
+      if (timeToWait < 0L) {
+        this.updatesBlockedMs.add(now - startTime);
+        LOG.info("Failed to unblocking updates for region " + this + " '"
+          + Thread.currentThread().getName() + "' in time. The region is still busy.");
+        throw new RegionTooBusyException("region is flushing");
{code}
typo: to unblocking updates -> to unblock updates
Should we include -timeToWait, the amount of time we are unable to wait in the exception message
?
                
> 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: Amitanand Aiyer
>         Attachments: trunk-6423.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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