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From "Jim Kellerman (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-69) [hbase] Make cache flush triggering less simplistic
Date Tue, 12 Feb 2008 14:25:24 GMT

    [ https://issues.apache.org/jira/browse/HBASE-69?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12568140#action_12568140
] 

Jim Kellerman commented on HBASE-69:
------------------------------------

> Billy Pearson - 12/Feb/08 01:56 AM
> I thank we are still missing something when I talk about hlog build up I mean there is
never a removal of 
> the hlogs unless there is a split or a shutdown.

As I explained previously, the only time that HLogs are garbage collected, is when either
the log fills, or
when the region server shuts down. Since there are not many updates coming in in the situation
you
described, the log will not fill and consequently old logs will not be garbage collected.

HBASE-440, will add optional log rolling, and log rolling when a region is closed in addition
to the current
log rolling when the log fills. Both of these new events will cause logs to be garbage collected.
Region
server shutdown will delete all the old logs.


> [hbase] Make cache flush triggering less simplistic
> ---------------------------------------------------
>
>                 Key: HBASE-69
>                 URL: https://issues.apache.org/jira/browse/HBASE-69
>             Project: Hadoop HBase
>          Issue Type: Improvement
>          Components: regionserver
>            Reporter: stack
>            Assignee: Jim Kellerman
>             Fix For: 0.2.0
>
>         Attachments: patch.txt, patch.txt, patch.txt, patch.txt, patch.txt, patch.txt,
patch.txt, patch.txt, patch.txt, patch.txt, patch.txt, patch.txt
>
>
> When flusher runs -- its triggered when the sum of all Stores in a Region > a configurable
max size -- we flush all Stores though a Store memcache might have but a few bytes.
> I would think Stores should only dump their memcache disk if they have some substance.
> The problem becomes more acute, the more families you have in a Region.
> Possible behaviors would be to dump the biggest Store only, or only those Stores >
50% of max memcache size.  Behavior would vary dependent on the prompt that provoked the flush.
 Would also log why the flush is running: optional or > max size.
> This issue comes out of HADOOP-2621.

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