[squid-users] Configure accelerator mode to serve from cache when source server not available

Squid Users:

I am trying to determine which set of timeout-related configuration
options would result in the following behavior:

We currently use a squid proxy as an HTTP accelerator for serving
graphical charts. The hostname 'charts.altosresearch.com' resolves to an
IP address/port on which squid (v3.0) is running. The 'defaultsite'
option is set to 'www.altosresearch.com', which actually generates the
graphical charts. All of this works very well:

http://charts.altosresearch.com/AltosCharts/CA/SAN+FRANCISCO/94115/median_price/a/1,2,3,4/m/e/mf/552.png

However, there are times when in production we have to take the
apache/tomcat server at 'www.altosresearch.com' offline for maintenance.
During these times, any requests to 'charts.altosresearch.com' will fail
because the squid proxy's attempt to validate the cached version fails.

Instead, I would like to configure squid to observe the following rule:
If the connection to www.altosresearch.com fails (returns 400/500 code,
or connection times out after XX seconds), then attempt to serve the
response using a cached object. The configuration variable
'minimum_expiry_time' seems related, but not sufficient.

Any recommendations would be greatly appreciated.

Regards,
Jason
Received on Tue Jan 22 2008 - 11:24:50 MST