Server Selection

Greg Whalin gwhalin at
Tue Dec 6 13:59:10 UTC 2005

Ivan Krstic wrote:
> Lee Kemp wrote:
>>Yeah, so say if i had one webserver that has
>>set as there memcached server ips, will this cause issue with  duplicate
>>items in my cache etc..? or would the hash still work out ok?
> This is solely dependent on the client implementation. You mentioned you
> were using the Java API, and from my one-minute glance at its source, it
>  looks like servers are internally placed into buckets in the order
> given at instantiation, and the cache key's CRC is transformed directly
> to a bucket array index, so you can't have servers listed in different
> orders in your clients if you don't want useless copies of the information.
> This should be easily solved by patching SockIOPool to sort the given
> server list before transforming it to a bucket array. If any of your
> clients has a server list whose length differs from any other's,
> however, you're bound to get unnecessary duplication, and there's no
> easy way around that.
> Greg Whalin, the JAVA memcached API author, is on the list, so he'll
> correct me if I misread his code.

This is 100% correct.  I guess I had never envisioned people putting the 
order in different.  I would not feel comfortable re-sorting the list in 
the event that the user intentionally set the order for some reason 
(can't think of a very compelling one off the top of my head, but does 
not mean there is not one).


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