Re: Returning JSON output from a handler thread still running?

> On Thursday 18 June 2009 14:57:27 Torbjörn Lager wrote:
>> Hello,
>>
>> Please have a look at the following code:
>> :- use_module(library('http/thread_httpd')).
>> :- use_module(library('http/http_dispatch')).
>> :- use_module(library('http/json')).
>> :- use_module(library('http/http_json')).
>> :
>> :- http_handler('/doit', doit, [spawn([alias(test)])]).
>>
>> doit(_Requestl) :-
>>     reply_json(json([a=result])),
>>     thread_get_message(Event),
>>     process(Event).
>>
>> :- http_server(http_dispatch, [port(5000)]).
>>
>> The call to thread_get_message/1 blocks (as it should), which seems to
>> imply that no JSON is returned to the browser (until I kill the
>> server). Does it have to be that way (I don't see why)? Is there any
>> way I can send JSON to the client and still keep the thread on the
>> server running?
>
> Not easily. The whole infrastructure is designed to deal with finishing
> the reply on completion of the handler. What you can do is enable
> session management (you need that anyway) and create a thread that is
> associated to the session. That is where you have the state-full
> computation and you send messages back and forth between the HTTP
> handlers and the session thread to communicate queries and results.
>
> Would be nice to have a demo using this scenario in the HTTP server
> examples directory ...
>
> More in general, I'm looking for good examples for this (and other)
> packages.  If you have things to share or are willing to write examples,
> please share them.
>
>        Cheers --- Jan
>
>> (What I'm trying to find here is a way to ask for one solution at the
>> time for a Prolog goal entered in a web interface. I have written code
>> that should have worked, had only the above worked... Maybe there are
>> other ideas for how to accomplish what I want to do? I've looked at
>> Uwe Lestas N-Queens demo, but it striked me as too complicated, and I
>> really would like to work against the SWI webserver...)
>>
>> Thanks in advance!
>>
>> Best regards,
>> Torbjörn
>
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