[racket] Web server

It wouldn't have a big impact on the server. The big question is how
to effectively use multi-core in Racket programs generally.

Futures are really only good for numerical codes that stay in the JIT,
which doesn't sound like most Web programs. That said, it is trivial
to implement:

#lang racket/base
(require racket/future
         web-server/servlet-env
         web-server/http)

(define (fib n)
  (if (< n 2)
    1
    (+ (fib (- n 1))
       (fib (- n 2)))))

(define (start req)
  (touch
   (future
    (λ ()
      (response/xexpr
       `(html
         (body
          (p "It's "
             ,(number->string
               (fib (random 20)))))))))))

(serve/servlet start)

Boom! That's a servlet that uses multi-core to handle every request...
of course, it probably doesn't pay in this or most other programs.

Places are for more coarse-grained things and you can pass file
descriptors, so it's feasible to have a TCP accepter that feeds work
to a group of places servicing the requests. However, places must not
use mutation to communicate higher-order values (they can communicate
flat values like numbers with mutation), so they couldn't share
continuations. It would be trivial to use serializable continuations
or to implement a continuation manager that stored all the
continuations in a single place. Session affinity doesn't really make
a lot of sense in the continuation context, fwiw.

My guess is that you could spend less than 100 lines to implement the
continuation manager and the place-based worker setup. (This is based
on the normal server setup just being 127 lines and the manager
interface being implemented in as little as 40 lines.) This might be
worth it.

Jay


On Wed, Jul 16, 2014 at 4:09 PM, Brian Adkins <racketusers at lojic.com> wrote:
> I haven't looked into the Racket web server much yet, so I'd like to understand the implications of this.
>
> My experience is with stateless http app servers (primarily with Unicorn Ruby servers at the moment), so firing up a number of worker processes and having something like nginx proxy to them works well to fully utilize all cores.
>
> I think I read that the Racket web server makes use of continuations, so I expect some sort of process affinity would be necessary, where a given user's requests are always proxied to the same worker process - is that right? Is it common to use multiple web server processes in Racket web apps?
>
> In your estimation, what is the feasibility of adding multi-core support to the Racket web server? For example, is it reasonably feasible and on the current roadmap, or would it require massive changes to the web server?
>
> Thanks,
> Brian
>
> On Jul 16, 2014, at 8:42 AM, Jay McCarthy wrote:
>
>> It does not use multiple cores if they are available.
>>
>> Jay
>>
>> On Wed, Jul 16, 2014 at 7:02 AM, Sean Kemplay <sean.kemplay at gmail.com> wrote:
>>> Hello,
>>>
>>> I am interested in the racket web server for some micro services. Just
>>> wondering if by default it runs across multiple cores or if it is restricted
>>> to one due to threads in racket.
>>>
>>> Regards,
>>> Sean
>>>
>>>
>>> ____________________
>>>  Racket Users list:
>>>  http://lists.racket-lang.org/users
>>>
>>
>>
>>
>> --
>> Jay McCarthy
>> http://jeapostrophe.github.io
>>
>>           "Wherefore, be not weary in well-doing,
>>      for ye are laying the foundation of a great work.
>> And out of small things proceedeth that which is great."
>>                          - D&C 64:33
>> ____________________
>>  Racket Users list:
>>  http://lists.racket-lang.org/users
>



-- 
Jay McCarthy
http://jeapostrophe.github.io

           "Wherefore, be not weary in well-doing,
      for ye are laying the foundation of a great work.
And out of small things proceedeth that which is great."
                          - D&C 64:33