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https://issues.apache.org/jira/browse/CASSANDRA-8672?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14391314#comment-14391314
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Sylvain Lebresne commented on CASSANDRA-8672:
---------------------------------------------
Apologies, for some reason I didn't understood you were talking of the commit
that is within {{beginAndRepairPaxos}}. So I agree, that commit should
definitively throw {{WriteType.CAS}} (I think it's an oversight that it
doesn't), and in fact, the patches look good to me so I've committed them. I'll
therefore close this issue. If someone wants to discuss further splitting
{{WriteType.CAS}} into more precise values (since that end up being suggested
even though that's orthogonal to the issue fixed), feel free to open a separate
issue (but as I mentioned above, I'm personally not entirely convinced that
it's entirely wise).
> Ambiguous WriteTimeoutException while completing pending CAS commits
> --------------------------------------------------------------------
>
> Key: CASSANDRA-8672
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8672
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Stefan Podkowinski
> Assignee: Tyler Hobbs
> Priority: Minor
> Labels: CAS
> Fix For: 3.0
>
> Attachments: storyproxybean-2.0-8672.txt, storyproxybean-2.1-8672.txt
>
>
> Any CAS update has a chance to trigger a pending/stalled commit of any
> previously agreed on CAS update. After completing the pending commit, the CAS
> operation will resume to execute the actual update and also possibly create a
> new commit. See StorageProxy.cas()
> Theres two possbile execution paths that might end up throwing a
> WriteTimeoutException:
> cas() -> beginAndRepairPaxos() -> commitPaxos()
> cas() -> commitPaxos()
> Unfortunatelly clients catching a WriteTimeoutException won't be able to tell
> at which stage the commit failed. My guess would be that most developers are
> not aware that the beginAndRepairPaxos() could also trigger a write and
> assume that write timeouts would refer to a timeout while writting the actual
> CAS update. Its therefor not safe to assume that successive CAS or SERIAL
> read operations will cause a (write-)timeouted CAS operation to get
> eventually applied. Although some [best-practices
> advise|http://www.datastax.com/dev/blog/cassandra-error-handling-done-right]
> claims otherwise.
> At this point the safest bet is possibly to retry the complete business
> transaction in case of an WriteTimeoutException. However, as theres a chance
> that the timeout occurred while writing the actual CAS operation, another
> write could potentially complete it and our CAS condition will get a
> different result upon retry.
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