Thanks, this is basically the solution. Can I do header override in squid to add this if the origin does not send this header? Would it make sense for squid to keep the state of the origin server for a few seconds, so it dose not have to contact it when it is not accessible on each individual request? Something like: 1. If origin responds to a request, set origin state to active. 2. If origin does not respond to a request, set origin state to "not active". This expires after a few seconds. 3. If origin state is not defined, it is assumed to be active. 4. If origin state is "not active", do not forward more than one request at a time. Sounds little bit like a can of worms :) Elli -----Original Message----- From: Chris Woodfield [mailto:rekoil@xxxxxxxxxxxxx] Sent: Thursday, June 25, 2009 9:36 AM To: Amos Jeffries; Myles Merrell Cc: Squid Users Subject: Re: Serving from the cache when the origin server crashes Take a careful look at the stale-if-error Cache-control header, as described below: http://tools.ietf.org/html/draft-nottingham-http-stale-if-error-01 In a nutshell, this allows you to force squid to serve up objects if the origin is down, even if those objects are stale, for a configurable number of seconds after the object's original stale timestamp. However, you'll still have the overhead of squid attempting to reach the origin, failing, then serving up the stale object on each request - as such, I'd highly recommend making sure that if you use this, you shut down the server in such a way that it generates an ICMP Destination Unreachable reply when squid attempts to connect. If you take the server off the air completely, squid will have to wait for network timeouts before returning the stale content, which your users will notice. Of course, you'll need to make sure that squid has your site cached in its entirety - it can't retrieve not-cached content from a dead server :) Amos, can you confirm that 3.x supports this? I'm using it in 2.7. -C
