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From "Sylvain Lebresne (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-3934) Short read protection is broken
Date Mon, 20 Feb 2012 18:51:34 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-3934?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sylvain Lebresne updated CASSANDRA-3934:
----------------------------------------

    Attachment: 3934.txt

Patch is against 1.0. The patch:
* don't retry if we have enough columns to satisfy the initial query
* keep the original count intact even if we do multiple retries.
* optimize the number of columns asked by a retry based on the ratio of number of column got/total
asked on the initial query.
                
> Short read protection is broken
> -------------------------------
>
>                 Key: CASSANDRA-3934
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3934
>             Project: Cassandra
>          Issue Type: Bug
>    Affects Versions: 1.0.2
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>             Fix For: 1.0.8, 1.1.0
>
>         Attachments: 3934.txt
>
>
> When a read needs to do more than one retry (due to short reads), the originalCount is
not preserved by the retry leading to returning more than the requested number of columns.
> Moreover, when a retried read checks whether more retry is needed, it doesn't compare
the number of live column retrieved against the original number of columns requested by the
user, but against the number of columns requested during the retry, making it much more likely
to actually do one more retry.
> This catch by the two tests 'short_read_test' and 'short_read_reversed_test' at https://github.com/riptano/cassandra-dtest/blob/master/consistency_test.py
that are failing intermittently.

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