Gianugo Rabellino wrote:
Stefano Mazzocchi wrote:
...
Question: (and an important one)
Suppose you have a resource like
/images/logo
that you hit with two different user agent and that a pipeline renders differently depending on the user agent, how can a proxy behave friendly to this? do we have a way to specify that a specific request has to be matched not only against a URI but also against the user-agent that requested it?
This can be done in a theory, once (and if) we'll have real proxy support in place. The first thing that can be done is starting to have real "Etag" support: an "Etag" is an unique identifier (think checksum) that represents the given URI from a server side view. This means that the same URI can lead to different etags being generated, according to internal server logic (request parameters, user agents, you name it). ù
Since an Etag is just a string, I guess that the cache key could do the job, but I'm not sure that it might be the better way security wise (you'll end up handing to the world your private cache keys, I'm not sure that this is a good thing). Also, Etags are useless if there is no conditional request handling: the proxy will ask Cocoon "give me that URI, identified by this Etag, if not modified since this timestamp": Cocoon must be able to analyze that query and reply either with an 304 status code (not modified) or with a 200 with the actual content.
In this particular case, however, the cleanest solution is using the HTTP/1.1 "Vary:" header. This header is supposed to contain all the request fields that must match for a proxy to decide that a resource is still valid even if requested by different users. Here you can specify that the user-agent is one of such headers, but:
0. this is one of the most undocumented headers around;
1. you still have to support Etags too (don't really know why);
2. there is no advanced feature like regular expressions or substring (proxies might implement it, but it's outside your control), so slightly different user agents (language, version, operating systems) will lead to regeneration;
3. I dare you to find a clean solution from the sitemap POV to express this kind of conditions. :-)
Ahem... http://cvs.apache.org/viewcvs.cgi/xml-cocoon2/src/java/org/apache/cocoon/selection/BrowserSelector.java?rev=1.7&content-type=text/vnd.viewcvs-markup ObjectModelHelper.getResponse(objectModel).addHeader("Vary", "User-Agent"); Vadim --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, email: [EMAIL PROTECTED]
