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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5930) Periodically flush the Memstore?
Date Wed, 24 Apr 2013 18:19:16 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5930?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13640745#comment-13640745
] 

Lars Hofhansl commented on HBASE-5930:
--------------------------------------

Sorry if I seem difficult with this one... How about a theme like this:
* We record the time of the first edit made to the memstore since the last flush. We can even
improve this and only record the time of the last unlogged edit made.
* Periodically we run the chore, if the recorded time of that first edit is older than a configurable
X then we flush the memstore.

That would:
# be simpler
# clearly limit the maximum an edit will stay in the memstore without being flushed

                
> Periodically flush the Memstore?
> --------------------------------
>
>                 Key: HBASE-5930
>                 URL: https://issues.apache.org/jira/browse/HBASE-5930
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Lars Hofhansl
>            Assignee: Devaraj Das
>            Priority: Minor
>             Fix For: 0.95.1
>
>         Attachments: 5930-1.patch, 5930-2.1.patch, 5930-2.2.patch, 5930-2.3.patch, 5930-2.4.patch,
5930-wip.patch
>
>
> A colleague of mine ran into an interesting issue.
> He inserted some data with the WAL disabled, which happened to fit in the aggregate Memstores
memory.
> Two weeks later he a had problem with the HDFS cluster, which caused the region servers
to abort. He found that his data was lost. Looking at the log we found that the Memstores
were not flushed at all during these two weeks.
> Should we have an option to flush memstores periodically. There are obvious downsides
to this, like many small storefiles, etc.

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