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From "Stu Hood (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-2191) Multithread across compaction buckets
Date Fri, 08 Apr 2011 07:11:06 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-2191?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Stu Hood updated CASSANDRA-2191:
--------------------------------

    Attachment: 0005-Add-a-harness-to-allow-compaction-tasks-that-need-to-a.txt
                0004-Allow-multithread-compaction-to-be-disabled.txt
                0003-Expose-multiple-compactions-via-JMX-and-a-concrete-ser.txt
                0002-Use-the-compacting-set-of-sstables-to-schedule-multith.txt
                0001-Add-a-compacting-set-to-DataTracker.txt

* Implemented "acquire the write lock long enough to schedule" for major, cleanup and scrub:
it's alone in patch 0005 for clarity
* Removed the JMX methods I had deprecated before, and added a method that returns serialized
objects for more programmatic access. The serialized object is concrete CompactionInfo, which
replaces (I|A)CompactionInfo

> Multithread across compaction buckets
> -------------------------------------
>
>                 Key: CASSANDRA-2191
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2191
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Stu Hood
>            Assignee: Stu Hood
>            Priority: Critical
>              Labels: compaction
>             Fix For: 0.8
>
>         Attachments: 0001-Add-a-compacting-set-to-DataTracker.txt, 0002-Use-the-compacting-set-of-sstables-to-schedule-multith.txt,
0003-Expose-multiple-compactions-via-JMX-and-a-concrete-ser.txt, 0004-Allow-multithread-compaction-to-be-disabled.txt,
0005-Add-a-harness-to-allow-compaction-tasks-that-need-to-a.txt
>
>
> This ticket overlaps with CASSANDRA-1876 to a degree, but the approaches and reasoning
are different enough to open a separate issue.
> The problem with compactions currently is that they compact the set of sstables that
existed the moment the compaction started. This means that for longer running compactions
(even when running as fast as possible on the hardware), a very large number of new sstables
might be created in the meantime. We have observed this proliferation of sstables killing
performance during major/high-bucketed compactions.
> One approach would be to pause compactions in upper buckets (containing larger files)
when compactions in lower buckets become possible. While this would likely solve the problem
with read performance, it does not actually help us perform compaction any faster, which is
a reasonable requirement for other situations.
> Instead, we need to be able to perform any compactions that are currently required in
parallel, independent of what bucket they might be in.

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