[racket] web-server and comet-like requests?

2011/2/22 Danny Yoo <dyoo at cs.wpi.edu>:
> On Tue, Feb 22, 2011 at 12:51 PM, Jay McCarthy <jay.mccarthy at gmail.com> wrote:
>> The Web Server will kill connections after a relatively short timeout.
>> You'll get an exception when you finally try to use the connection.
>> This isn't very nice for COMET. You'll have to reset the timeout on
>> the connection manually.
>
>
> Two comments:
>
> 1.  Is output-response from web-server/http/response documented?  I
> searched and couldn't find it.  It seems a critical function for
> writing dispatchers.

It is not documented. I imagined people would just throw
next-dispatcher and drop to a lifted procedure (dispatch-lift) or
their servlet.

>
> 2.  If a user cancels an http request (say, by pressing the stop
> button on the browser), is that observable from the web-server side of
> things?

You can't tell the difference between that and the connection closing
for any other reason.

Jay

>
>
> I have something like this now, but unfortunately, it's not handling
> the scenario from question 2 correctly:
>
> ;;;;;;;;;;;;;;;;;;;
> #lang racket
>
> ;; Comet demonstration
>
> (require web-server/web-server
>         web-server/http/bindings
>         web-server/http/response
>         web-server/http/response-structs)
>
> (define ch (make-channel))
>
> (void
>  (thread (lambda ()
>
>           (define (my-dispatcher conn req)
>             (cond [(exists-binding? 'comet (request-bindings req))
>                    (handle-comet conn req)]
>                   [else
>                    (handle-default conn req)]))
>         (serve #:dispatch my-dispatcher #:port 8080))))
>
>
> (define (handle-comet conn req)
>  (let ([v (sync ch)])
>    (with-handlers ([exn:fail? (lambda (exn)
>                                 (printf "exn: ~s\n" exn)
>                                 (thread (lambda () (channel-put ch v))))])
>      (output-response conn
>                       (response/full 200 #"Okay"
>                                      (current-seconds)
>                                      #"text/plain; charset=utf-8"
>                                      empty
>                                      (list #"" (string->bytes/utf-8
> (format "~s" v))))))))
>
> (define (handle-default conn req)
>  (output-response conn '(html (body (p "hello world")))))
>
> (define (send-to-client v)
>  (channel-put ch v))
>



-- 
Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University
http://faculty.cs.byu.edu/~jay

"The glory of God is Intelligence" - D&C 93