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https://issues.apache.org/jira/browse/CASSANDRA-4310?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yuki Morishita updated CASSANDRA-4310:
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Attachment: 4310.txt
Initial patch attached to get feedback(still writing unit test for this).
I introduced _max_concurrent_tasks_ as new compaction option of
LeveledCompactionStrategy(default is 1) to specify number of tasks to run in
parallel.
List of sstables set is chosen by the algorithm similar to above in
LeveledManifest#getCompactionCandidates.
If there are 2 or more sets to compact, then ParallelLeveledCompactionTask gets
created with its own executor, and performs compaction in parallel.
I feel I need some unit test for selecting list of sstables, so patch is still
in progress. will update if it's done.
> Multiple independent Level Compactions in Parallel
> --------------------------------------------------
>
> Key: CASSANDRA-4310
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4310
> Project: Cassandra
> Issue Type: New Feature
> Components: Core
> Affects Versions: 1.0.0
> Reporter: sankalp kohli
> Assignee: Yuki Morishita
> Labels: compaction, features, leveled, performance, ssd
> Fix For: 1.2.1
>
> Attachments: 4310.txt
>
>
> Problem: If you are inserting data into cassandra and level compaction cannot
> catchup, you will create lot of files in L0.
> Here is a solution which will help here and also increase the performance of
> level compaction.
> We can do many compactions in parallel for unrelated data.
> 1) For no over lapping levels. Ex: when L0 stable is compacting with L1, we
> can do compactions in other levels like L2 and L3 if they are eligible.
> 2) We can also do compactions with files in L1 which are not participating in
> L0 compactions.
> This is specially useful if you are using SSD and is not bottlenecked by IO.
> I am seeing this issue in my cluster. The compactions pending are more than
> 50k and the disk usage is not that much(I am using SSD).
> I am doing multithreaded to true and also not throttling the IO by putting
> the value as 0.
>
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