Willy Tarreau 6b2e11be1e [MEDIUM] backend: implement consistent hashing variation ... Consistent hashing provides some interesting advantages over common hashing. It avoids full redistribution in case of a server failure, or when expanding the farm. This has a cost however, the hashing is far from being perfect, as we associate a server to a request by searching the server with the closest key in a tree. Since servers appear multiple times based on their weights, it is recommended to use weights larger than approximately 10-20 in order to smoothen the distribution a bit. In some cases, playing with weights will be the only solution to make a server appear more often and increase chances of being picked, so stats are very important with consistent hashing. In order to indicate the type of hashing, use : hash-type map-based (default, old one) hash-type consistent (new one) Consistent hashing can make sense in a cache farm, in order not to redistribute everyone when a cache changes state. It could also probably be used for long sessions such as terminal sessions, though that has not be attempted yet. More details on this method of hashing here : http://www.spiteful.com/2008/03/17/programmers-toolbox-part-3-consistent-hashing/		2009-10-09 07:17:58 +02:00
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common	[MINOR] tools: add a new get_next_id() function	2009-10-04 22:48:42 +02:00
import	[MAJOR] replace ultree with ebtree in wait-queues	2008-06-24 08:17:16 +02:00
proto	[MEDIUM] backend: implement consistent hashing variation	2009-10-09 07:17:58 +02:00
types	[MEDIUM] backend: implement consistent hashing variation	2009-10-09 07:17:58 +02:00