[jira] [Commented] (CASSANDRA-6106) QueryState.getTimestamp() & FBUtilities.timestampMicros() reads current timestamp with System.currentTimeMillis() * 1000 instead of System.nanoTime() / 1000

["Sylvain Lebresne (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-6106?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13783154#comment-13783154 ] 

Sylvain Lebresne commented on CASSANDRA-6106:
---------------------------------------------

Alright so for the sake of keeping things focused, I've opened CASSANDRA-6123 to actually fix the underlying issue. Let's focus this ticket on deciding whether having a better precision for timestamp in the meatime is worth it.

On the last attached patch, haven't had a proper look yet but will try to do so and follow-up asap.

> 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, microtimstamp_random.patch, microtimstamp_random_rev2.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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