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https://issues.apache.org/jira/browse/CASSANDRA-5667?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jeremy Hanna updated CASSANDRA-5667:
------------------------------------
Labels: LWT (was: )
> Change timestamps used in CAS ballot proposals to be more resilient to clock
> skew
> ---------------------------------------------------------------------------------
>
> Key: CASSANDRA-5667
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5667
> Project: Cassandra
> Issue Type: Improvement
> Affects Versions: 2.0 beta 1
> Environment: n/a
> Reporter: Nick Puz
> Assignee: Jonathan Ellis
> Priority: Minor
> Labels: LWT
> Fix For: 2.0 beta 1
>
> Attachments: 5667.txt
>
>
> The current time is used to generate the timeuuid used for CAS ballots
> proposals with the logic that if a newer proposal exists then the current one
> needs to complete that and re-propose. The problem is that if a machine has
> clock skew and drifts into the future it will propose with a large timestamp
> (which will get accepted) but then subsequent proposals with lower (but
> correct) timestamps will not be able to proceed. This will prevent CAS write
> operations and also reads at serializable consistency level.
> The work around is to initially propose with current time (current behavior)
> but if the proposal fails due to a larger existing one re-propose (after
> completing the existing if necessary) with the max of (currentTime,
> mostRecent+1, proposed+1).
> Since small drift is normal between different nodes in the same datacenter
> this can happen even if NTP is working properly and a write hits one node and
> a subsequent serialized read hits another. In the case of NTP config issues
> (or OS bugs with time esp around DST) the unavailability window could be much
> larger.
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