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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-3430) Break Big Compaction Lock apart
Date Tue, 19 Mar 2013 03:01:18 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3430?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13605978#comment-13605978
] 

Jonathan Ellis commented on CASSANDRA-3430:
-------------------------------------------

You're right, there's a race because I assumed that if getNextBackgroundTask is already running
on CompactionExecutor, it will be part of the compaction activity we wait to finish.  Unfortunately
I don't see a good way to actually make that true; collector.beginCompaction doesn't run until
we're well into the task (because we can't create the necessary , and finishCompaction runs
before we unmark.

So instead I'm using the compaction marker itself as an indication that we've successfully
cancelled everything.  Which is obviously more correct, but I'd already found a couple compaction-marker
leaks so I was hoping to avoid making more of those obvious.  I did the next best thing and
added a timed loop after which we give up and log.

I've also made pause and getNextBackgroundTask serialized, so we can guarantee that after
pause completes, no new tasks will be generated; or put another way, pause can't run until
in-progress tasks are done being created.  This shouldn't be necessary for correctness but
it does make it easier to reason about.

Pushed to https://github.com/jbellis/cassandra/tree/3430-4, with fix for 2I pause.  (3430-3
tried another approach that didn't pan out...)
                
> Break Big Compaction Lock apart
> -------------------------------
>
>                 Key: CASSANDRA-3430
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3430
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>            Priority: Minor
>              Labels: compaction
>             Fix For: 2.0
>
>         Attachments: 3430-1.0.txt, 3430-1.1.txt, 3430-v2.txt, 3430-v3.txt
>
>


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