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https://issues.apache.org/jira/browse/HADOOP-2615?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12565213#action_12565213
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Billy Pearson commented on HADOOP-2615:
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I got a second ideal on this to help with hot spots
If we could add a way to set a priority for compaction's this would help with
the hot spots regions building up to many map files flushes.
Example if we have a region with 25 map files and one with 10
Region with 25 map files would have a priority of 25
and the one with 10 map files have a priority of 10 we would compact the region
with 25 before 10
If we could add/update the priority when we do a flush then the compactor could
work on region that need it the most in order.
> Add max number of mapfiles to compact at one time giveing us a minor & major
> compaction
> ---------------------------------------------------------------------------------------
>
> Key: HADOOP-2615
> URL: https://issues.apache.org/jira/browse/HADOOP-2615
> Project: Hadoop Core
> Issue Type: Improvement
> Components: contrib/hbase
> Reporter: Billy Pearson
> Priority: Minor
> Fix For: 0.17.0
>
> Attachments: flag-v2.patch, flag.patch, twice.patch
>
>
> Currently we do compaction on a region when the
> hbase.hstore.compactionThreshold is reached - default 3
> I thank we should configure a max number of mapfiles to compact at one time
> simulator to doing a minor compaction in bigtable. This keep compaction's
> form getting tied up in one region to long letting other regions get way to
> many memcache flushes making compaction take longer and longer for each region
> If we did that when a regions updates start to slack off the max number will
> eventuly include all mapfiles causeing a major compaction on that region.
> Unlike big table this would leave the master out of the process and letting
> the region server handle the major compaction when it has time.
> When doing a minor compaction on a few files I thank we should compact the
> newest mapfiles first leave the larger/older ones for when we have low
> updates to a region.
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