[Catalyst] Re: modules for conditional GET ?
* Dami Laurent (PJ) laurent.d...@justice.ge.ch [2010-01-18 08:35]: So clients should keep asking for those pages at each request, and depending on the If-Modified-Since header and on the timestamp for the config file, the server can decide if it's worth recomputing the page for that client, or rather send a cheap 304 Not Modified. I suggest you send an ETag and check `If-None-Match` (possibly just a hash of the timestamp for the config file) instead of (or if you have HTTP/1.0 clients, in addition to) relying on the timestamp and `If-Modified-Since`. Beyond that: It’s easy to write a module that will conserve bandwidth using these headers, by hashing the body after all computation is done and checking whether to send it or just a 304. But conserving server CPU requires intimate knowledge of both the model and the structure of the controllers. It seems hard to find a generically useful abstraction beyond a utility method or two for setting the headers. Regards, -- Aristotle Pagaltzis // http://plasmasturm.org/ ___ List: Catalyst@lists.scsys.co.uk Listinfo: http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/catalyst Searchable archive: http://www.mail-archive.com/catalyst@lists.scsys.co.uk/ Dev site: http://dev.catalyst.perl.org/
Re: [Catalyst] Re: modules for conditional GET ?
On Sun, Jan 17, 2010 at 11:35 PM, Dami Laurent (PJ) laurent.d...@justice.ge.ch wrote: Indeed, this is exactly what I want to do. The app has a config file (not a Catalyst config file, but another file having to do with business logic), and some super-users have a mechanism for hot uploading of a new config to the server, at any time. A few app pages are expensive to compute, and they depend on the client and on that config file. So clients should keep asking for those pages at each request, and depending on the If-Modified-Since header and on the timestamp for the config file, the server can decide if it's worth recomputing the page for that client, or rather send a cheap 304 Not Modified. Be careful about using timestamps if you are running multiple web servers behind a load balancer (or may expand to where you will be behind a balancer). Here's a read on Etags: http://developer.yahoo.net/blog/archives/2007/07/high_performanc_11.html For resources such as css, js, images I tend to create URLs that include an md5. Those include cache headers that don't expire and thus when the content changes the URL changes. I have also done that with text/html pages, but it's less common. For a config file you can send the config through Object::Signature to get an md5. You could recalculate and cache that whenever a new config is uploaded. For static pages (for non-logged in users) the pages tend to get cached for some number of minutes as it's not critical that a change is seen exactly the same time by all users. Dynamic content is not cached, of course, but elements of the page may be cached in memcached. -- Bill Moseley mose...@hank.org ___ List: Catalyst@lists.scsys.co.uk Listinfo: http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/catalyst Searchable archive: http://www.mail-archive.com/catalyst@lists.scsys.co.uk/ Dev site: http://dev.catalyst.perl.org/
RE: [Catalyst] Re: modules for conditional GET ?
-Message d'origine- De : Aristotle Pagaltzis [mailto:pagalt...@gmx.de] Envoyé : samedi, 16. janvier 2010 15:34 À : catalyst@lists.scsys.co.uk Objet : [Catalyst] Re: modules for conditional GET ? * Dami Laurent (PJ) laurent.d...@justice.ge.ch [2010-01-14 16:05]: For some actions of a Catalyst app, I would like to implement conditional GET (using If-Modified-Since HTTP header), where the timestamp of one config file decides whether the page should be refreshed or not --- this is because that page is quite expensive to compute. I agree with the others who have responded, but they didn't explain why theirs was the right answer, so: You're not checking whether any state has changed since the last GET to decide whether to recompute. That is the case in which conditional GET would be appropriate. That would allow you to avoid recomputing the page indefinitely as long as no state changes necessitate it, but it requires that the clients keep asking. Indeed, this is exactly what I want to do. The app has a config file (not a Catalyst config file, but another file having to do with business logic), and some super-users have a mechanism for hot uploading of a new config to the server, at any time. A few app pages are expensive to compute, and they depend on the client and on that config file. So clients should keep asking for those pages at each request, and depending on the If-Modified-Since header and on the timestamp for the config file, the server can decide if it's worth recomputing the page for that client, or rather send a cheap 304 Not Modified. Cheers, L. Dami ___ List: Catalyst@lists.scsys.co.uk Listinfo: http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/catalyst Searchable archive: http://www.mail-archive.com/catalyst@lists.scsys.co.uk/ Dev site: http://dev.catalyst.perl.org/
