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From <Jeremy.Truel...@barclayscapital.com>
Subject RE: Does Cassandra use vector clocks
Date Wed, 23 Feb 2011 01:37:12 GMT
More a less yes you must handle the synchronization, this only really becomes an issue when
multiple hosts hit Cassandra and want to hit the same row/column at the same time, which is
certainly possible but may not be common depending on your use case. 

this has a bit of info on the column level clock
http://wiki.apache.org/cassandra/DataModel

you can write your own clock resolution in a high level client like hector
http://patricioechague.blogspot.com/2010/12/how-to-create-custom-clockresolution-in.html

single writer timestamp resolution
http://patricioechague.blogspot.com/2010/10/evaluating-timestamp-resolution.html

Vector clocks was more of a Dynamo thing, I read a write up somewhere on some of reasons why
Cassandra puts this issue on the user but I can't locate it currently unfortunately. Hope
this helps.

-----Original Message-----
From: tijoriwala.ritesh [mailto:tijoriwala.ritesh@gmail.com] 
Sent: Tuesday, February 22, 2011 8:13 PM
To: cassandra-user@incubator.apache.org
Subject: Re: Does Cassandra use vector clocks


Thanks for the quick reply. I found this ticket
https://issues.apache.org/jira/browse/CASSANDRA-580 which talks about vector
clock support in Cassandra but it was marked as "won't fix". It would be
insightful to know why it was rejected.

If Cassandra relies on timestamps, does it mean that clients have to be
clock synchronized? This is very difficult in distributed systems.
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