Simple Consistent Hash for Memcache in Ruby

Consistent hashing is a scheme that provides hash table functionality in a way that the addition or removal of one slot does not significantly change the mapping of keys to slots. In contrast, in most traditional hash tables, a change in the number of array slots causes nearly all keys to be remapped. By using consistent hashing, only K/n keys need to be remapped on average, where K is the number of keys, and n is the number of slots.

servers = ['memcache1', 'memcache2', 'memcache3', 'memcache4']
servers[ 'product-1'.hash % servers.size ]
 
servers[ 'product-1'.hash % servers.size ] => "memcache4"
servers[ 'product-2'.hash % servers.size ] => "memcache1"