[Twisted-web] Concurrency in a twisted.web application

[Ananda Tallur]

I have sent a question a few days ago, concerning having concurrency  
in a twisted.web application.

I have a web application, which has some features which imply doing  
long calculations.
My need would be to have the web application still responsive to  
other http requests, while processing a calculation triggered by  
another request.

Therefore, more preciserly, for a request which needs to trigger  
calculations, I would like the following scenario to take place :
-> the resource serving the request launches a dedicated thread or  
process to perform the calculation
-> the resource returns a defered, so that twisted.web core gets the  
control back and continues serving other requests
-> when the calculation thread/process has finished its calculation,  
a callback is called to finish processing the request.

I have no idea of how to implement this, and can't find a  
documentation or an example for this kind of concurrent web  
application with twisted.web.

Does anyone has already written something close, or knows a  
documentation / example which could help me ?

I really thank everyone in advance.

Anand

On 16 nov. 05, at 11:50, Ananda Tallur wrote:

> Dear twisted.web developpers and users,
>
> I have written a twisted application for viewing and exporting movies.
> These movies are in a format specific to my company.
> I use : twisted 2.1.0, twisted.web 0.5.0, and nevow 0.5.0 (all html  
> templates are written using nevow).
>
> In this web application, there is a feature for exporting a movie  
> file into mpeg, and sending it to the client web browser (file  
> download).
>
> This feature is handled by a resource object which is a subclass of  
> static.File.
> Exporting a movie into mpeg implies :
> -> opening the original video file
> -> doing the conversion (which can take as long as 1 minute or more)
> -> sending the resulting mpeg file to the browser (file download)
>
> The problem is that while the twisted web application is working  
> handling the export request, the twisted web server is not  
> responsive to any other HTTP request, as long as the video  
> conversion and file transfer is not finished.
>
> I would like to know if there is a standard or recommanded way of  
> setting up concurrency into a twisted.web application.
> And also if there is a sample program available somewhere.
>
> I would like my web application to be still responsive to other  
> HTTP requests while :
> -> file conversion to mpeg is being processing
> -> mpeg file is being transfered to the client browser (which is  
> handled by a static.File subclass resource)
>
>
> Thank you very much for all your answers.
> I appreciate very much working with twisted.web and interested to  
> get more insight into the way twisted core handles requests.
>
> Anand
>
>
>
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