[jira] [Commented] (CASSANDRA-9649) Paxos ballot in StorageProxy could clash

["sankalp kohli (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-9649?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15326656#comment-15326656 ] 

sankalp kohli commented on CASSANDRA-9649:
------------------------------------------

cc [~slebresne] Did you create a JIRA to fix issue introduced in this JIRA? Please let me know. 

> Paxos ballot in StorageProxy could clash
> ----------------------------------------
>
>                 Key: CASSANDRA-9649
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9649
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Coordination
>            Reporter: Stefania
>            Assignee: Stefania
>            Priority: Minor
>             Fix For: 2.0.17, 2.1.8, 2.2.0 rc2
>
>
> This code in {{StorageProxy.beginAndRepairPaxos()}} takes a timestamp in microseconds but divides it by 1000 before adding one. So if the summary is null, ballotMillis would be the same for up to 1000 possible state timestamp values:
> {code}
>     long currentTime = (state.getTimestamp() / 1000) + 1;
>     long ballotMillis = summary == null
>                                  ? currentTime
>                                  : Math.max(currentTime, 1 +    UUIDGen.unixTimestamp(summary.mostRecentInProgressCommit.ballot));
>     UUID ballot = UUIDGen.getTimeUUID(ballotMillis);
> {code}
> {{state.getTimestamp()}} returns the time in micro seconds and it ensures to add one microsecond to any previously used timestamp if the client sends the same or an older timestamp. 
> Initially I used this code in {{ModificationStatement.casInternal()}}, introduced by CASSANDRA-9160 to support cas unit tests, but occasionally these tests were failing. It was only when I ensured uniqueness of the ballot that the tests started to pass reliably.
> I wonder if we could ever have the same issue in StorageProxy?
> cc [~jbellis] and [~slebresne] for CASSANDRA-7801



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