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From: Glen Campbell <glen.campbell@rackspace.com>
To: "users@trafficserver.apache.org" <users@trafficserver.apache.org>
Subject: Re: ATS to return cached contents on 500 error
Thread-Topic: ATS to return cached contents on 500 error
Thread-Index: AQHLogx9ek91ak7irUCv7S/BirAW25Os2+4A
Date: Wed, 22 Dec 2010 19:39:59 +0000
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The stale-if-error directive should cause that behavior, but I'm not
certain if it's been implemented in ATS yet (online documentation refers
to "future versions").

You could certainly write a custom extension to do that if you don't want
to rely upon the client headers.

http://www.mnot.net/blog/2007/12/12/stale

On 12/22/10 1:13 PM, "John Cheng" <johnlicheng@gmail.com> wrote:

>Can ATS be configured (as a forward proxy) to return cached contents
>when the origin server returns an error?
>
>This may be an unusual use case, and I'll describe the scenario I
>think where it might be needed. I want to use ATS as a forward proxy
>between our application servers and external web services. This allows
>us to reduce the number of web services calls and use local caching to
>increase performance. In this case, one of our external partners has a
>flaky web service system. The contents of their web service does not
>change often and is suitable for caching the contents daily. However,
>some times, their web service will return a 404 or 500 for a whole
>day, then go back to normal the next day. So the behavior I'd like is
>for our system to check to origin server for any changes. If there is
>a change, update the local cache. If there is an error (404, 500), or
>time out then continue to use the cached content.
>
>I looked into the configuration file and it does not appear ATS
>supports this kind of behavior. I am wondering if this is possible
>with ATS.
>
>--=20
>---
>John L Cheng


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