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https://issues.apache.org/jira/browse/CASSANDRA-6106?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13779577#comment-13779577
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Jonathan Ellis commented on CASSANDRA-6106:
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I'm saying that even before you start talking about drift, we're correlating 
millis/nanos and saying, This Is The Reference Point For Zero Micros, but we 
could actually be 100 micros into the current ms, we could be 900, we have no 
way to tell.
                
> QueryState.getTimestamp() & FBUtilities.timestampMicros() reads current 
> timestamp with System.currentTimeMillis() * 1000 instead of System.nanoTime() 
> / 1000
> ------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-6106
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6106
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: DSE Cassandra 3.1, but also HEAD
>            Reporter: Christopher Smith
>            Priority: Minor
>              Labels: collision, conflict, timestamp
>         Attachments: microtimstamp.patch
>
>
> I noticed this blog post: http://aphyr.com/posts/294-call-me-maybe-cassandra 
> mentioned issues with millisecond rounding in timestamps and was able to 
> reproduce the issue. If I specify a timestamp in a mutating query, I get 
> microsecond precision, but if I don't, I get timestamps rounded to the 
> nearest millisecond, at least for my first query on a given connection, which 
> substantially increases the possibilities of collision.
> I believe I found the offending code, though I am by no means sure this is 
> comprehensive. I think we probably need a fairly comprehensive replacement of 
> all uses of System.currentTimeMillis() with System.nanoTime().

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