[racket] loop in stateless webserver acts different/weird

Ended up doing

#lang racket

(require web-server/http
         web-server/http/bindings
         web-server/lang/web ;not web-server/servlet
         web-server/templates)

For some reason, module+ main does not like #lang web-server.

However, the code now fails with:

Cannot stuff (kont #<procedure:...abort-resume.rkt:145:3>) into a URL
because it contains non-serializable pieces. Convert
#<procedure:next-text-handler> to a serializable struct

Does this fall under 'serial->native' part of the documentation or do
I need to make a serializable struct of  txts argument? It's a just
list of strings, which I thought would be harmless in this context.


On Fri, Aug 24, 2012 at 10:21 PM, Jay McCarthy <jay.mccarthy at gmail.com> wrote:
> When you use
>
> #lang web-server
>
> You have to use
>
> web-server/lang/web ---
> http://docs.racket-lang.org/web-server/stateless.html#(part._lang/web)
>
> rather than
>
> web-server/servlet/web (which you are getting from web-server/servlet)
>
> The problem is that your send/suspend/dispatch is the STATEFUL one,
> not the STATELESS one and so there is no state instance available.
>
> Jay
>
> On Fri, Aug 24, 2012 at 8:38 AM, J G Cho <gcho at fundingmatters.com> wrote:
>> So I have a module that runs fine in a web server. However when I
>> tried it in "stateless" server, it fails (msg: No instance for id: 1)
>> with a very short stacke trace. I run it by itself using (module+ main
>> ...) then it runs but it does not work as intended (more on this
>> below).
>>
>> So here are "toy" versions of what my module does which produces
>> similar behavior.
>>
>> First, the version that works (uses the attached file as template):
>>
>> #lang racket
>>
>> (require web-server/servlet
>>          web-server/templates)
>>
>> ;; insert into UI Template and then dish out HTML
>> (define (form-template msg k-url output)
>>   (response/full
>>    200 #"Okay"
>>    (current-seconds) TEXT/HTML-MIME-TYPE
>>    empty
>>    (list (string->bytes/utf-8 (include-template "ui.html")))))
>>
>> (define (all-ups xs)
>>   (if (null? xs)
>>       ""
>>       (string-append (string-upcase (car xs))
>>                      "<br/>"
>>                      (all-ups (cdr xs)))))
>>
>> (define (main-loop txts parser helper)
>>   (local [(define (response-generator embed/url)
>>             (form-template
>>              (helper (reverse txts))
>>              (embed/url next-text-handler)
>>              (format "~a" (parser (reverse txts)))))
>>
>>           (define (next-text-handler req)
>>             (main-loop (cons (extract-binding/single 'quote
>> (request-bindings req))
>>                              txts)
>>                        parser
>>                        helper))]
>>
>>     (send/suspend/dispatch response-generator)))
>>
>> (define (start initial-req)
>>   (main-loop '()
>>              (lambda (xs)
>>                (cond
>>                  [(null? xs) "To undo, just go back (short-cut
>> alt+left arrow)."]
>>                  [else (all-ups xs)]))
>>              (lambda (xs)
>>                (cond
>>                  [(null? xs) "Start:"]
>>                  [else (format "Input ~a: ready for more." (add1
>> (length xs)))]))))
>>
>> (provide start)
>>
>> (module+ main
>>   (require web-server/servlet-env)
>>
>>   (serve/servlet start
>>                  #:quit? #t
>>                  #:listen-ip #f
>>                  #:log-file "debug.log" #:port 8082 #:launch-browser? #t
>>                  #:log-format 'parenthesized-default
>>                  #:servlet-path "/quotes"))
>>
>> Here is the version that does not work (main difference is in module+ area):
>>
>> #lang racket
>>
>> (require web-server/servlet
>>          web-server/templates)
>>
>> ;; insert into UI Template and then dish out HTML
>> (define (form-template msg k-url output)
>>   (response/full
>>    200 #"Okay"
>>    (current-seconds) TEXT/HTML-MIME-TYPE
>>    empty
>>    (list (string->bytes/utf-8 (include-template "ui.html")))))
>>
>> (define (all-ups xs)
>>   (if (null? xs)
>>       ""
>>       (string-append (string-upcase (car xs))
>>                      "<br/>"
>>                      (all-ups xs))))
>>
>> (define (main-loop txts parser helper)
>>   (local [(define (response-generator embed/url)
>>             (form-template
>>              (helper (reverse txts))
>>              (embed/url next-text-handler)
>>              (format "~a" (parser (reverse txts)))))
>>
>>           (define (next-text-handler req)
>>             (main-loop (cons (extract-binding/single 'quote
>> (request-bindings req))
>>                              txts)
>>                        parser
>>                        helper))]
>>
>>     (send/suspend/dispatch response-generator)))
>>
>> (define (start initial-req)
>>   (main-loop '()
>>              (lambda (xs)
>>                (cond
>>                  [(null? xs) "To undo, just go back (short-cut
>> alt+left arrow)."]
>>                  [else (all-ups xs)]))
>>              (lambda (xs)
>>                (cond
>>                  [(null? xs) "Start:"]
>>                  [else (format "Input ~a: ready for more." (add1
>> (length xs)))]))))
>>
>> (provide start)
>>
>> (module+ main
>>   (require web-server/servlet-env
>>            web-server/stuffers)
>>
>>   (define stuffer
>>     (stuffer-chain
>>      serialize-stuffer
>>      (md5-stuffer (build-path (current-directory) "urls"))))
>>
>>   (serve/servlet start
>>                  #:quit? #t
>>                  #:listen-ip #f
>>                  #:log-file "debug.log" #:port 8082 #:launch-browser? #t
>>                  #:log-format 'parenthesized-default
>>                  #:stateless? #t #:stuffer stuffer
>>                  #:servlet-path "/quotes"))
>>
>> The failed version seems to have no memory (ie the previous inputs are
>> NOT available).
>>
>> How can I fix this?
>>
>> jGc
>>
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>
>
>
> --
> 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