On sön, 2008-08-10 at 20:25 -0700, Rob Williams wrote: > HTCP, Cache Digest, whatever), do I need all requests to my array / > mesh to come to a 'master' squid acting as a router/load balancer? Or > do I put a load balancer in front of the array and distribute http > requests randomly to the squids in the array? I would use a load balancer.. > The problem I'm having is if I put a load balancer in front of my > squid array then each squid must be aware of all other peers in order > for the squid array to act as a large cache. Yes.. > This results in > forwarding loops and other problems when using ICP and carp that I've > been unable to get around so far. There is no need for ICP when using CARP. You should not see forwarding loops in a correct CARP setup. In a crossed sibling relation you may see forwarding loops, and the workaround is to use cache_peer_access to deny siblings to be used if the request was received from a sibling (any sibling), There is no intra-array CARP routing in Squid, only CARP forwarding. A quite efficient CARP setup looks like: 1. A simple load balancer distributing the connections among the caches. Or even DNS round-robin if you like (the load balancer mainly makes it easier if you need to take one server down for service or if there is a problem..) 2. A CARP squid layer, with no disk cache but a reasonable cache_mem. This receives requests from the load balancer and acts as hot object cache and distributed CARP HTTP load balancer. 3. A caching Squid layer with the disk cache, used as a parent CARP cache_peer relation by the CARP squids. These have the origin servers as parents. 2 & 3 runs as two Squid instances on the same servers, with each server having a CARP squid listening on the load balanced port and a caching squid listening on another port only used for the CARP forwarding (or another IP if you prefer..) On all Squids a relatively short connect_timeout is set. ICP is not used. (no-query on all cache_peer) On multi-core servers >2 cores there may be benefit to run more than one CARP instance per server. > instance as it assumes a linear array instead of a hierarchy, but at > this point I'd be happy to see ANY cache protocol example that would > distribute the cached objects in a squid cluster. The simplest setup is ICP + proxy-only. But it's not as efficient as CARP and will result in noticeably increased duplication of content over time. Regards Henrik
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