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Posted to server-dev@james.apache.org by "Tellier Benoit (JIRA)" <ji...@apache.org> on 2015/06/17 11:41:00 UTC
[jira] [Resolved] (MAILBOX-209) A data race is possible with
Cassandra modseq generation
[ https://issues.apache.org/jira/browse/MAILBOX-209?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Tellier Benoit resolved MAILBOX-209.
------------------------------------
Resolution: Fixed
I just commited changes for this issue.
Patch was contributed by Matthieu Baechlor.
> A data race is possible with Cassandra modseq generation
> --------------------------------------------------------
>
> Key: MAILBOX-209
> URL: https://issues.apache.org/jira/browse/MAILBOX-209
> Project: James Mailbox
> Issue Type: Bug
> Reporter: Tellier Benoit
> Attachments: MAILBOX-209-rebased.patch, fix_cassandra_modseq_provider.patch
>
>
> The Cassandra mailbox implementation proceed as follow to increase the modseq :
> - a first call to Cassandra to increase the modseq value for a given mailbox
> - a second call allow us to retrieve the current value.
> Note that you can not do it in a single call...
> In a distributed environment, imagine that :
> - for a mailbox the current modseq is n
> - server A increments modseq. Modseq is n+1
> - server B increments modseq. Modseq is n+2
> - server A and B then retrieve the modseq value and have a duplicated modseq : they for instance both can assign n+2 value to a different message.
> The problem can be solved using conditionnal updates with lightweight transactions.
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