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Re: [Chicken-users] Starting up spiffy for dynamic content

From: Norman Gray
Subject: Re: [Chicken-users] Starting up spiffy for dynamic content
Date: Wed, 09 Mar 2016 15:01:56 +0000

Peter, hello.

On 8 Mar 2016, at 20:41, Peter Bex wrote:

On Tue, Mar 08, 2016 at 02:48:00PM +0000, Norman Gray wrote:

So you mean including handlers like:

(define (vhost-handler cont)
(let ((uri (uri-path (request-uri (current-request)))))
  (if (string=? (cadr uri) "wibble") ;; we want to handle URIs
like /wibble/...
      (send-response status: 'ok
                     body: (format "<p>Good: request was ~S
(vhost)</p>" uri)
                     headers: '((content-type text/html)))
(vhost-map `((".*" . ,vhost-handler)))

That's how it was intended, yes.  I've added something similar to the
wiki with a link to slightly extended (but somewhat outdated) example
from a demonstration.

The new section 'A simple dynamic web page example' is perfect, in combination with the pointer to the spiffy+sxml example.

I marginally adjusted the linked webserver.scm to use sxml-serializer rather than the full-blown sxml transform egg (was that the 'outdated' you meant). I've attached the result.

OK: that's a (very) nice design -- I'll do that.

But may I suggest that vhost-map is not, perhaps, the best name for
this structure, since the intended functionality is much more
general than mapping vhosts.  As I mentioned, I guessed that might
be a route to the solution, but based on the name, on the fact it's
documented in a section called 'Virtual hosts', and since the
example in that section is about handling virtual hosts, I got the
impression that the author was firmly steering me away from more
open-ended cleverness.  Caolan suggested that I'm not (thankfully)
alone in misinterpreting this.

Well, it is a mapping for which handler to use for which vhost.  That
is also the topmost place where dispatching happens for incoming
requests, so it's the place where you'd add custom handlers.

I could add some intermediate parameter like "request-handler", which
then defaults to some procedure that handles the request like the
current implementation does (try to serve a file), but it would be
one more level of indirection which is basically just what "continue"
does now.

Would that be sensible?

I don't think that would be necessary and would, as you say, be a further level of indirection. Yesterday afternoon, I did put together a potential patch for spiffy.scm which may have the same idea (attached for interest), but the vhost-map (once one understands what it's intended for) seems to be completely general.

Perhaps dispatch-handler-map, or handler-map, or something like
that, would signal the intent more clearly, along with an example
such as the above.

Not sure that would be much clearer. Also, it would break compatibility.

Indeed: it's not obvious what the best name is, though 'handle/host' seemed to push the right buttons for me.

One would of course export a (define vhost-map fancy-new-name) for compatibility.

Since the car of the alist is a host pattern,
then perhaps the word 'host' should be in the name, but in that case
perhaps handle/host might be suitable (and if anything's being
changed, then it might be nice to have a clear catch-all host
pattern, such as #t, or to permit the list elements to be a
continuation thunk as well as a string-thunk pair).  Thus:

 ("foo\\.bar\\.com" . ,(lambda (continue) ...))
 (#t . ,my-catch-all-handler))

I think that would only complicate things, and cause more confusion
as to the format of this list.

I agree.

It's a wiki, feel free to improve the wording in places where it's

There's nothing I can usefully add to the change you've made, but I'll bear the suggestion in mind for what I expect to be lots of future engagement with these docs.

And thanks, Andy, for the pointer to uri-match (and for the mention of Knodium, which I intend to investigate further).

All the best,


Norman Gray  :
SUPA School of Physics and Astronomy, University of Glasgow, UK

Attachment: spiffy-with-dispatcher.diff
Description: Text document

Attachment: spiffy-sxml-demo.scm
Description: Text document

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