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Date: Wed, 2 Dec 2009 15:10:20 +0000 (UTC)
From: "Lars George (JIRA)" <jira@apache.org>
To: hbase-dev@hadoop.apache.org
Subject: [jira] Commented: (HBASE-2018) Updates to .META. blocked under high
 MemStore load
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    [ https://issues.apache.org/jira/browse/HBASE-2018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12784866#action_12784866 ] 

Lars George commented on HBASE-2018:
------------------------------------

So testing for me is not going too well. Overall the patch is not harming anything, I say +1. For my testing I am struggling apparently with a too small cluster :(

> Updates to .META. blocked under high MemStore load
> --------------------------------------------------
>
>                 Key: HBASE-2018
>                 URL: https://issues.apache.org/jira/browse/HBASE-2018
>             Project: Hadoop HBase
>          Issue Type: Bug
>    Affects Versions: 0.20.2
>            Reporter: Jean-Daniel Cryans
>            Assignee: Jean-Daniel Cryans
>            Priority: Blocker
>             Fix For: 0.20.3, 0.21.0
>
>         Attachments: HBASE-2018.patch
>
>
> I discovered this on Lars' cluster. The symptom was the good old:
> {code}
> 09/11/30 08:10:26 INFO mapred.JobClient: Task Id : attempt_200911250121_0011_r_000010_1, Status : FAILED
> org.apache.hadoop.hbase.client.RetriesExhaustedException: Trying to contact region server Some server, retryOnlyOne=true, index=0, islastrow=false, tries=9, numtries=10, i=14, listsize=20, region=prev-docs,de68fb97795ef3d936a3f10ff8790253,1259573366564 for region prev-docs,ccea967e66ccb53d83c48849c3a23f21,1259542138868, row 'ccff8cd4ca871c41f4fa7d44cffed962', but failed after 10 attempts.
> Exceptions:
>         at org.apache.hadoop.hbase.client.HConnectionManager$TableServers$Batch.process(HConnectionManager.java:1120)
>         at org.apache.hadoop.hbase.client.HConnectionManager$TableServers.processBatchOfRows(HConnectionManager.java:1201)
>         at org.apache.hadoop.hbase.client.HTable.flushCommits(HTable.java:605)
>         at org.apache.hadoop.hbase.client.HTable.put(HTable.java:470)
>         at org.apache.hadoop.hbase.mapreduce.TableOutputFormat$TableRecordW
> {code}
> But the load wasn't that heavy, just lots of splitting going on. Looking at the logs, I see a split taking more than 4 minutes which is explained by this happening on the RS hosting .META. :
> {code}
> 2009-11-30 08:08:39,922 INFO org.apache.hadoop.hbase.regionserver.MemStoreFlusher: Forced flushing of prev-docs,2c9d51e57b20decd5c6419d23ede822b,1259542273901 because global memstore limit of 1.6g exceeded; currently 1.6g and flushing till 1021.9m
> ...
> 2009-11-30 08:12:33,743 DEBUG org.apache.hadoop.hbase.regionserver.HRegion: Finished memstore flush of ~22.9m for region prev-docs,c8fea4fbbc41e746d960854ed4d41dd6,1259587143838 in 14160ms, sequence id=13677, compaction requested=false
> 2009-11-30 08:12:33,744 INFO org.apache.hadoop.hbase.regionserver.MemStoreFlusher: Forced flushing of prev-docs,39c2995d955c041d21f4dc4a0d0dbf6c,1259587061295 because global memstore limit of 1.6g exceeded; currently 1.0g and flushing till 1021.9m
> {code}
> So we should not block updates to .META. for any reason. I'm pretty sure this issue explains other issues we've seen on the mailing list.

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