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From Norman Maurer <nor...@apache.org>
Subject Re: Curious as to how Cassandra handles the following
Date Sun, 26 Sep 2010 18:45:41 GMT
Comments inside..

2010/9/26 Lucas Nodine <lucasnodine@gmail.com>:
> I'm looking at a design where multiple clients will connect to Cassandra and
> get/mutate resources, possibly concurrently.  After planning a bit, I ran
> into the following scenero for which I have not been able to research to
> find an answer sufficient for my needs.  I have found where others have
> recommended Zookeeper for such tasks, but I want to determine if there is a
> simple solution before including another product in my design.
>
> Make the following assumption for all following situations:
> Assuming multiple clients where a client is someone accessing Cassandra
> using thrift.  All reads and writes are performed using the QUORUM
> consistency level.
>
> Situation 1:
> Client A ("A") connects to Cassandra and requests a QUORUM consistency level
> get of an entire row.  At or very shortly thereafter (before A's request
> completes), Client B ("B") connects to Cassandra and inserts (or mutates) a
> column (or multiple columns) within the row.
>
> Does A receive the new data saved by B or does A receive the data prior to
> B's save?

Shoud receive A stuff.
>
> Situaton 2:
> B connects and mutates multiple columns within a row.  A requests some data
> therein while B is processing.
>
> Result?

Depends.. is it done in BatchMutate or not ?

>
> Situation 3:
> B mutates multiple columns within multiple rows.  A requests some data
> therein while B is processing.
>
> Result?

See above..

>
> Justification: At certain points I want to essentially lock a resource (row)
> in cassandra for exclusive write access (think checkout a resource) by
> setting a flag value of a column within that row.  I'm just considering race
> conditions.
>
You will need to use cages or something like that..


> Thanks,
>
> Lucas Nodine

Bye,
Norman

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