Re: [squid-users] Quick question about squid serving images

Angelo Höngens wrote:
> On 19-11-2009 9:46, NublaII Lists wrote:
>> I have squid configured (working on it ;)) as a reverse proxy.
>>
>> My understanding (and I can be wrong) is that once I request an image,
>> next requests for that image will not reach the web server in any way
>> until it expires, either manually or reaches end of life... is that
>> correct?
>
> If you would have configured everything correctly, yes..
>
>
>> I am asking because I can see on my apache logs a ton of hits on
>> images that squid should be caching, and still arrive to the www
>> server, so either I don't have it configured properly or I don't
>> really understand how squid works on reverse proxy mode ;)
>
> It should work like you say, but either squid is not configured
> correctly, or the application tells squid not to cache. Squid decides
> what it can cache, based on the response headers from the apache
> application. Post those headers. The squidclient tool is really useful.
>
> Run this on your squid machine (example, assuming your squid listens on
> port 80):
>
> squidclient -p 80 -h apacheserver http://domain/image.jpg | head -n 15
>
> Increase or decrease the 'head -n X' value to show all the headers, but
> not to return the binary content. It should return something like this:
>
> HTTP/1.1 200 OK
> Cache-Control: public
> Content-Type: image/jpeg
> Expires: Thu, 19 Nov 2009 09:08:51 GMT
> Last-Modified: Thu, 19 Nov 2009 04:51:23 GMT
> Server: Microsoft-IIS/7.0
> X-AspNet-Version: 2.0.50727
> X-Powered-By: ASP.NET
> Date: Thu, 19 Nov 2009 08:54:51 GMT
> Connection: close
> Content-Length: 2845
>
> Based on these response headers, Squid decides to cache or not.
> Particularly interesting is the 'Cache-Control' header. From there on,
> google further ;)
>
>

The tool provided by Yahoo! at http://www.redbot.org or the IRCache
cacheability engine prodvide useful reports for identifying what a proxy
can and cannot do with any given public URL.

Amos

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