Friday, October 2, 2009

Multiple parent proxies

If you would like to have more than one parent proxy you can add more cache_peer directives; one for each parent. Now you can define either weight or round-robin to control the way Squid will communicate with the proxies: while weight tells Squid to prefer one cache over another, round-robin tries to spread connections evenly among the defined caches.

First of all a simple example for two parent proxies:

cache_peer proxy.isp1.com parent 8080 0 no-query no-digest default
cache_peer proxy.isp2.com parent 8080 0 no-query no-digest


If you define more than one parent proxy you might want to set one as the default proxy, which is used as a last resort.

An example for weight:

cache_peer proxy.isp1.com parent 8080 0 no-query no-digest weight=1
cache_peer proxy.isp2.com parent 8080 0 no-query no-digest weight=2
In this example it is likely that the proxy from the second ISP will be favored over the first one.

And here an example for round-robin:

cache_peer proxy.isp1.com parent 8080 round-robin no-query
cache_peer proxy.isp2.com parent 8080 round-robin no-query
cache_peer proxy.isp3.com parent 8080 round-robin no-query


All connections to our proxy would be round-robined among these three caches. Because Squid treats all parents equally, it is currently not possible to define a weight here, e.g. to forward 50% of the requests to the first proxy and 25% to the second and third proxy respectively.

Rf. http://www.christianschenk.org/blog/using-a-parent-proxy-with-squid/
http://www.visolve.com/squid/squid24s1/glossary.php#round-robin

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