[Twisted-Python] Control the number of parallel system calls

Chris Miles miles.chris at gmail.com
Wed Sep 19 06:57:26 EDT 2007

I've done something very similar.  I control the number of concurrent  
child processes by simply keeping a counter of how many are active at  
any one time.  The main loop that polls a queue will only accept new  
jobs if the counter is less than the configuration-defined limit.

I didn't find anything Twisted-specific to limit the number of forked  
processes, but it was easy to implement in my own logic.


On 19 Sep 2007, at 11:26, Daniel de la Cuesta wrote:

> Hi,
> I am developing a video conversion server. To process the video  
> conversion I use the method "getProcessOutput" to call "ffmpeg".
> The user upload the video using a HTTP POST and each video must be  
> converted to 8 or 10 output formats.
> Currently, all the conversions for each video are processed in  
> parallel, what I want to do is to control the number of parallel  
> system calls to "ffmpeg". For example I only want 2 processes at  
> the same time and when one of them finishes the next process start.
> How can I do that?
> Is there any function in Twisted that implements that?
> Thank you

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