Re: Streaming responses with Guile's web modules

[Roel Janssen <roel@gnu.org>]

Amirouche Boubekki <amirouche@hypermove.net> writes:

> On 2018-09-18 21:42, Roel Janssen wrote:
>> Dear Guilers,
>>
>> I'd like to implement a web server using the (web server) module, but
>> allow for “streaming” results.  The way I imagine this would look like,
>> is something like this:
>>
>> (define (request-handler request body)
>>   (values '((content-type . (text/plain)))
>>           ;; This function can build its response by writing to
>>           ;; ‘port’, rather than to return the whole body as a
>>           ;; string.
>>           (lambda (port)
>>             (format port "Hello world!"))))
>>
>> (run-server request-handler)
>>
>> Is this possible with the (web server) module?  If so, how?
>
> What you describe is exactly how it works. The second value can
> be a bytevector, #f or a procedure that takes a port as argument.
>
> Here is an example use [0] and here is the code [1]
>
> [0]
> https://framagit.org/a-guile-mind/culturia.next/blob/master/culturia/web/helpers.scm#L34
> [1]
> https://git.savannah.gnu.org/cgit/guile.git/tree/module/web/server.scm#n198
>
> Regards

Thanks for your quick and elaborate reply!  I didn't realize that in
writing the example I had written a working example.

Looking at memory usage, it looks as if it puts all bytes produced by
that function into memory at once before sending the HTTP response over
the network.  Is that observation correct?  If so, can it be avoided?

Kind regards,
Roel Janssen