[jira] Commented: (CASSANDRA-1083) Improvement to CompactionManger's submitMinorIfNeeded

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-1083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12886777#action_12886777 ] 

Jonathan Ellis commented on CASSANDRA-1083:
-------------------------------------------

it would be nice to make getBuckets suck less in 0.6.4.  deeper changes would have to wait for 0.7 imo.

> Improvement to CompactionManger's submitMinorIfNeeded
> -----------------------------------------------------
>
>                 Key: CASSANDRA-1083
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1083
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Ryan King
>            Assignee: Ryan King
>            Priority: Minor
>             Fix For: 0.7
>
>         Attachments: 1083-configurable-compaction-thresholds.patch, compaction_simulation.rb
>
>
> We've discovered that we are unable to tune compaction the way we want for our production cluster. I think the current algorithm doesn't do this as well as it could, since it doesn't sort the sstables by size before doing the bucketing, which means the tuning parameters have unpredictable results.
> I looked at CASSANDRA-792, but it seems like overkill. Here's an alternative proposal:
> config operations:
>  minimumCompactionThreshold
>  maximumCompactionThreshold
>  targetSSTableCount
> The first two would mean what they currently mean: the bounds on how many sstables to compact in one compaction operation. The 3rd is a target for how many SSTables you'd like to have.
> Pseudo code algorithm for determining whether or not to do a minor compaction:
> {noformat} 
> if sstables.length + minimumCompactionThreshold -1 > targetSSTableCount
>   sort sstables from smallest to largest
>   compact the up to maximumCompactionThreshold smallest tables
> {noformat} 

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