ketama - a consistent hashing algo for memcache clients

Steven Grimm sgrimm at
Tue Apr 10 17:00:29 UTC 2007

That was actually the next major thing on our memcached to-do list. 
Thanks -- you may have saved us a bit of work there!


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:
> 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?
> RJ

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