Header parameters and check URL exists in cache?

[Jack Bates <6n...@nottheoilrig.com>]

Hi, do you know of any examples of parsing parameters in header field 
values that you can suggest to me? e.g. matching charset=UTF-8 in 
"Content-Type: ...; charset=UTF-8" or rel=duplicate in "Link: <...>; 
rel=duplicate"

Also can you suggest any examples of checking if a given URL already 
exists in the cache or not?

I am attempting a plugin [1] to take advantage of Metalink [2] to 
redirect clients to mirrors that already exist in the cache. I am trying 
to loop over RFC 6249 "Link: <...>; rel=duplicate" headers and check if 
the URL already exists in the cache

[1] https://github.com/jablko/dedup
[2] http://metalinker.org/

Re: Header parameters and check URL exists in cache?

[Leif Hedstrom <zw...@apache.org>]

On 5/6/12 1:24 PM, Jack Bates wrote:
> Hi, do you know of any examples of parsing parameters in header field 
> values that you can suggest to me? e.g. matching charset=UTF-8 in 
> "Content-Type: ...; charset=UTF-8" or rel=duplicate in "Link: <...>; 
> rel=duplicate"

No, there's not such parsing provided in the API.

>
> Also can you suggest any examples of checking if a given URL already 
> exists in the cache or not?

Technically, I *think* TSCcacheRead() can be used to check for the existence 
of an object in the HTTP cache, and perhaps even read the header for what is 
in cache. The caveat is that these APIs were not intended to work on the 
HTTP cache, but for your case, it might work. Only one way to find out.

Fwiw, the APIs TSCacheWrite(), TSCacheRead() etc. were intended for someone 
to store and retrieve non-HTTP cache objects. The core obviously uses the 
same underlying code for the HTTP cache, the complication is that it uses it 
in a way that is not exposed via current APIs (such that you could not get 
to the body of an HTTP object via these objects). There's an example 
protocol plugin that uses these APIs for storing content in the cache.

Cheers,

-- Leif