Re: [squid-users] index key generation mechanism?

On 22/08/11 18:28, Raymond Wang wrote:
> hi all:
>
>
>
> For the file of "somejs.js", there are two urls referring to it, for
> example: url1 is "http://www.a.com/somejs.js" and url2 is
> "http://www.a.com/somejs.js".
>
> by default, squid would use the above urls to generate certain key
> that would be used as index key to write/read the somejs.js file
> to/from memory.
>
> My question is that: could I affect the index key generation, so that
> squid could save the somejs.js file in memory only one object. for
> example, for url1, we can trim "http://www.a.com/somejs.js" to
> "somejs.js" and "http://www.a.com/somejs.js" to "somejs.js", then the
> key would be "somejs.js", e.g. use the file name (or some variants
> based on it) as index key. this way, we can "save" the two different
> urls (the referred files have the same content) as only one object in
> Squid.
>
> is it possible?
>

Possible. Yes. Easy no.

The key Squid uses is the public URL which the client is asking for.

YouTube is a well-known website which behaves like you describe. It is a
serious nightmare for a great many network admins.
http://wiki.squid-cache.org/ConfigExamples/DynamicContent/YouTube

The storeurl_rewrite feature experiment in squid-2.7 does exactly what
you describe.

Considering that 1) you must already have a list of patterns for
matching, and 2) you thus have a known location of at least one instance.

The safer, friendlier, and HTTP compliant method is to simply setup a
url_rewrite_program helper. Which tests URLs against your patterns and
emits "303:$new_url" when it finds a match on GET requests.

  ** by safer and friendlier, I mean that instead of potentially
poisoning caches all over the world with broken or corrupt data (see
recent T-mobile problems) all you do is break any load balancing on the
websites in question.

Amos

-- 
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