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Date: Mon, 13 Feb 2012 13:30:59 +0000 (UTC)
From: "Sylvain Lebresne (Updated) (JIRA)" <jira@apache.org>
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Subject: [jira] [Updated] (CASSANDRA-3862) RowCache misses Updates
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     [ https://issues.apache.org/jira/browse/CASSANDRA-3862?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sylvain Lebresne updated CASSANDRA-3862:
----------------------------------------

    Attachment: 3862_v3.patch
    
> RowCache misses Updates
> -----------------------
>
>                 Key: CASSANDRA-3862
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3862
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.0.7
>            Reporter: Daniel Doubleday
>         Attachments: 3862-v2.patch, 3862.patch, 3862_v3.patch, include_memtables_in_rowcache_read.patch
>
>
> While performing stress tests to find any race problems for CASSANDRA-2864 I guess I (re-)found one for the standard on-heap row cache.
> During my stress test I hava lots of threads running with some of them only reading other writing and re-reading the value.
> This seems to happen:
> - Reader tries to read row A for the first time doing a getTopLevelColumns
> - Row A which is not in the cache yet is updated by Writer. The row is not eagerly read during write (because we want fast writes) so the writer cannot perform a cache update
> - Reader puts the row in the cache which is now missing the update
> I already asked this some time ago on the mailing list but unfortunately didn't dig after I got no answer since I assumed that I just missed something. In a way I still do but haven't found any locking mechanism that makes sure that this should not happen.
> The problem can be reproduced with every run of my stress test. When I restart the server the expected column is there. It's just missing from the cache.
> To test I have created a patch that merges memtables with the row cache. With the patch the problem is gone.
> I can also reproduce in 0.8. Haven't checked 1.1 but I haven't found any relevant change their either so I assume the same aplies there.

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