[squid-users] Modifying error Responses.

Hello all,

I need a way to modify the body of a response when a server responds
with an error code. I have a suspicion that this may be possible with
squid, but I'm getting a bit confused by the terse documentation.

First a bit of background to better understand the problem.

We run a website that serves content for mobile phones. This content
resides on several backend servers, most of them live with partners
who provide our content. We have an "aggregator" that accepts requests
from mobile phones, and then in turn requests the content form one or
more backend servers. The content these backends deliver is xml, and
this xml gets transformed by our aggregator in to something a mobile
phone can display. We access these backends through a squid proxy to
have some caching.

Our problem is that sometimes the backend sends an error (404, 500
etc..) without a properly formed xml body. This causes a thread on our
aggregator to block until a timeout is reached. As a result a problem
on a backend can lead to resource depletion on our aggregator.

On possible solution would be to modify error responses. We want to
tack our own xml response body in to any errror response we get from
a backend.

I've done some reading, and came across ICAP, eCam and clientstreams.
From the little documentation that is available i'm not sure how to
attack this problem.
- I only want to modify http responses when the backend server sends
an error code (4xx, 5xx).
- I only want a simple modification. Basically swap out whatever body
in the response with our own.
- We currently use squid 2.6. We could move to 3.0 if needed.

Any suggestions as to what the best way to solve our problem would be
are welcome.

Krist van Besien

-- 
krist.vanbesien@gmail.com
krist@vanbesien.org
Bremgarten b. Bern, Switzerland
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