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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7925) TimeUUID LSB should be unique per process, not just per machine
Date Fri, 22 May 2015 14:28:18 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7925?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14556211#comment-14556211
] 

Sylvain Lebresne commented on CASSANDRA-7925:
---------------------------------------------

bq. It's currently used for paxos.

Right, and that's not a problem for Paxos.

bq. Also, I imagine we will still allow the clients to specify timestamps (esp for thrift)
in CASSANDRA-7919

We certainly will want to preserve backward compatibility (both for thrift and CQL), but doing
so mean that we will need to guarantee to 2 updates with the same (user provided) timestamp
actually *do* conflict, and this no matter what node the update hits. So in fact, we'll probably
have to hardcode a LSB to use for all update with user provided timestamp. In any case, I
think anticipating problems for CASSANDRA-7919 is a bit premature. It's not like we can't
change this if we really need to later.

In general, I'd prefer keeping it to a fixed LSB for a given process if possible: it's a tad
simpler, better for compression and a bit closer to the timeuuid RFC imo. And as of now, I
think that's good enough.

> TimeUUID LSB should be unique per process, not just per machine
> ---------------------------------------------------------------
>
>                 Key: CASSANDRA-7925
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7925
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Peter M├Ądel
>            Assignee: T Jake Luciani
>             Fix For: 2.2.x
>
>         Attachments: cassandra-uuidgen.patch
>
>
> as pointed out in [CASSANDRA-7919|https://issues.apache.org/jira/browse/CASSANDRA-7919?focusedCommentId=14132529&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14132529]
lsb collisions are also possible serverside.
> a sufficient solution would be to include references to pid and classloader within lsb.



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