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From Maki Watanabe <watanabe.m...@gmail.com>
Subject Re: Decorator Algorithm
Date Fri, 24 Jun 2011 02:53:17 GMT
A little addendum

Key := Your data to identify a row
Token := Index on the ring calculated from Key. The calculation is
defined in replication strategy.

You can lookup responsible nodes (endpoints) for a specific key with
JMX getNaturalEndpoints interface.

maki


2011/6/24 aaron morton <aaron@thelastpickle.com>:
> Various places in the code call IPartitioner.decorateKey() which returns a DecoratedKey<T>
which contains both the original key and the Token<T>
>
> The RandomPartitioner md5 to hash the key ByteBuffer and create a BigInteger. OPP converts
the key into utf8 encoded String.
>
> Using the token to find which endpoints contain replicas is done by the AbstractReplicationStrategy.calculateNaturalEndpoints()
implementations.
>
> Does that help?
>
> -----------------
> Aaron Morton
> Freelance Cassandra Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 23 Jun 2011, at 19:58, Jonathan Colby wrote:
>
>> Hi -
>>
>> I'd like to understand more how the token is hashed with the key to determine on
which node the data is stored - called decorating in cassandra speak.
>>
>> Can anyone share any documentation on this or describe this more in detail?   Yes,
I could look at the code, but I was hoping to be able to read more about how it works first.
>>
>> thanks.
>
>



-- 
w3m

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