ketama - a consistent hashing algo for memcache clients

Paul Querna chip at corelands.com
Tue Apr 10 17:13:59 UTC 2007


Richard Jones wrote:
> Every time we added memcached servers to the pool, the rehashing of all keys 
> would kill our database while the cache filled up again. We implemented a 
> consistent hashing algorithm that our memcached clients are now using to map 
> keys to servers. Now we can add new memcached servers without causing 
> chaos :)
> 
> Here is the blurb and the code:
> http://www.last.fm/user/RJ/journal/2007/04/10/392555/
> 
> Source download includes:
>  libketama, a c library
>  php_ketama, a php extension that uses the library
>  a pure java implementation
> 
> I'm interested in other approaches (or even if this is a concern for most 
> people?). I read about the lots-of-virtual-buckets concept, but didn't find 
> an implementation. Anyone already using consistent hashing for memcache?


Sweet.

I love it.

Is it possible to release the c library part under a less restrictive 
license than the GPL, like say an MIT or BSD license like memcached itself?

Thanks,

-Paul



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