Would any of this go away if we'd finally switched to Webmachine? Cheers Jan --
On 21 Jul 2011, at 02:09, Paul Davis wrote: > On Wed, Jul 20, 2011 at 6:32 PM, Randall Leeds <[email protected]> > wrote: >> On Wed, Jul 20, 2011 at 15:20, Paul Davis <[email protected]> >> wrote: >>> On Wed, Jul 20, 2011 at 5:15 PM, Randall Leeds <[email protected]> >>> wrote: >>>> On Wed, Jul 20, 2011 at 15:09, Paul Davis <[email protected]> >>>> wrote: >>>>> On Wed, Jul 20, 2011 at 5:03 PM, Travis Jensen <[email protected]> >>>>> wrote: >>>>>> couch_httpd.erl seems to be confused about what it wants to do with HEAD >>>>>> requests. >>>>>> >>>>>> On the one hand, it supports catching {http_head_abort, Resp} and will >>>>>> throw >>>>>> that in start_response/3 and start_response_length/4 if your method is >>>>>> set >>>>>> to HEAD. >>>>>> >>>>>> On the other hand, it sets all HEAD requests to GET, so no handler can >>>>>> ever >>>>>> know a HEAD request was made (instead, it lets Mochiweb strip the body). >>>>>> >>>>>> I can appreciate the simplicity of the latter, but >>>>>> the schizophrenic behavior seems odd. I've also got a custom handler that >>>>>> would really like to know if it is HEAD or GET (generating the body >>>>>> takes a >>>>>> lot of CPU, but I know its length because I store it in a document). >>>>>> >>>>>> First question: should Couch really set all HEAD requests to GET? >>>>>> (Personally, I think not) >>>>>> Second question: does anybody know how bad it would be to remove that >>>>>> HEAD >>>>>> -> GET mapping? >>>>>> >>>> >>>> It would be bad since a lot of the handlers specifically match against >>>> the method being GET. >>>> I have a ticket open to do smarter things with HEAD in general, >>>> especially as it relates to caching proxies and ETags: >>>> https://issues.apache.org/jira/browse/COUCHDB-941 >>>> >>>> It's something we should definitely set about fixing eventually, but I >>>> don't know what the priority is. >>>> >>>>>> Cheers. >>>>>> >>>>>> tj >>>>>> -- >>>>>> *Travis Jensen* >>>>>> *** >>>>>> *Read the Software Maven @ http://softwaremaven.innerbrane.com/ >>>>>> Read my LinkedIn profile @ http://www.linkedin.com/in/travisjensen >>>>>> Read my Twitter mumblings @ http://twitter.com/SoftwareMaven >>>>>> Send me email @ [email protected] >>>>>> >>>>>> **What kind of guy calls himself the Software Maven???** >>>>>> >>>>> >>>>> I don't have the answer at the tip of my fingers, but IIRC there was a >>>>> specific interaction that we had to do that so that something else >>>>> didn't break. I wonder if its possible to tag the request with a >>>>> special "is actually a HEAD request" thing so users can check. >>>> >>>> I don't like an "is actually a HEAD request" flag. >>>> Adding HEAD handlers is the right approach, but if we want to be lazy >>>> we could support a fallback to GET when we get a function_clause error >>>> trying to call the handler. >>>> >>> >>> Yeah, its definitely a hack. A fallback on function_clause would >>> definitely be much cleaner I think. Only thing is I tend to wonder if >>> there'd be a performance hit since our entire HTTP stack currently >>> relies on HEAD -> GET, which would be generate a lot of exception >>> handling. >> >> It'd only occur when people do a HEAD request, so normal operation >> would be fine? >> Clearly we'd want to log a warning or something and start implementing >> all the HEAD responses properly. >> > > Though I think some libraries will use HEAD requests to check if they > can short circuit some operations. No idea what sort of density that'd > be and it'd obviously be fairly lib/usecase specific. > > Also true, if we change this, adding real HEAD responses would be > useful. Granted in a webmachine world this would all Just Work. > >>> >>>>> >>>>> I'd search through the dev@ list for chatter on that mapping around >>>>> the time it was made. I'm pretty sure there was a thread that we did >>>>> some discussion on that. >>>>> >>>> >>> >>
