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From AJ ...@dude.podzone.net>
Subject Re: Docs: Token Selection
Date Wed, 15 Jun 2011 21:34:01 GMT
Vijay, thank you for your thoughtful reply.  Will Cass complain if I 
don't setup my tokens like in the examples?

On 6/15/2011 2:41 PM, Vijay wrote:
> All you heard is right...
> You are not overriding Cassandra's token assignment by saying here is 
> your token...
>
> Logic is:
> Calculate a token for the given key...
> find the node in each region independently (If you use NTS and if you 
> set the strategy options which says you want to replicate to the other 
> region)...
> Search for the ranges in each region independntly
> Replicate the data to that node.
>
> For multi DC cassandra needs nodes to be equally partitioned 
> within each dc (If you care that the load equally distributed).... as 
> well as there shouldn't be any collusion of tokens within a cluster....
>
> The documentation tried to explain the same and the example in the 
> documentation.
> Hope this clarifies...
>
> More examples if it helps....
>
> DC1 Node 1 : token 0
> DC1 Node 2 : token 8..
>
> DC2 Node 1 : token 4..
> DC2 Node 1 : token 12..
>
> or
>
> DC1 Node 1 : token 0
> DC1 Node 2 : token 1..
>
> DC2 Node 1 : token 8..
> DC2 Node 1 : token  7..
>
> Regards,
> </VJ>
>
>
>
> On Wed, Jun 15, 2011 at 12:28 PM, AJ <aj@dude.podzone.net 
> <mailto:aj@dude.podzone.net>> wrote:
>
>     On 6/15/2011 12:14 PM, Vijay wrote:
>>     Correction....
>>
>>     "The problem in the above approach is you have 2 nodes between 12
>>     to 4 in DC1 but from 4 to 12  you just have 1"
>>
>>     should be
>>
>>     "The problem in the above approach is you have 1 node between 0-4
>>     (25%) and and one node covering the rest which is 4-16, 0-0 (75%)"
>>
>>     Regards,
>>     </VJ>
>>
>
>     Ok, I think you are saying that the computed token range intervals
>     are incorrect and that they would be:
>
>     DC1
>     *node 1 = 0      Range: (4, 16], (0, 0]
>
>     node 2 = 4      Range: (0, 4]
>
>     DC2
>     *node 3 = 8      Range: (12, 16], (0, 8]
>
>     node 4 = 12   Range: (8, 12]
>
>     If so, then yes, this is what I am seeking to confirm since I
>     haven't found any documentation stating this directly and that
>     reference that I gave only implies this; that is, that the token
>     ranges are calculated per data center rather than per cluster.  I
>     just need someone to confirm that 100% because it doesn't sound
>     right to me based on everything else I've read.
>
>     SO, the question is:  Does Cass calculate the consecutive node
>     token ranges A.) per cluster, or B.) for the whole data center?
>
>     From all I understand, the answer is B.  But, that documentation
>     (reprinted below) implies A... or something that doesn't make
>     sense to me because of the token placement in the example:
>
>     "With NetworkTopologyStrategy, you should calculate the tokens the
>     nodes in each DC independantly...
>
>     DC1 node 1 = 0 node 2 = 85070591730234615865843651857942052864 DC2
>     node 3 = 1 node 4 = 850705917302346158658436518579
>     42052865"
>
>
>     However, I do see why this would be helpful, but first I'm just asking if this token
assignment is absolutely mandatory
>     or if it's just a technique to achieve some end.
>
>
>
>


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