[zeromq-dev] Client Server Model in Python

[Robert Kern]

On 8/24/10 8:17 AM, Martin Sustrik wrote:
> Abishek,
>
>>      * I think the if the message processing logic takes lot of time, how
>>        can I thread the process of processing the message (in Python)
>
> AFAIK Python does not provide real threads, just green threads. So the
> only option would be to run several python processes, connected to a
> single central queue device (zmq_queue).

Python does provide real OS threads. However, the interpreter has a Global 
Interpreter Lock such that only one Python bytecode instruction runs at a time, 
usually. The GIL is released during I/O and some other long computations done 
inside C code that does not need to use the interpreter's data structures. Since 
0MQ is running in its own thread and does not use the interpreter's data 
structures, it does not grab hold of the GIL. The network I/O and the processing 
already happen in separate threads. That's one of the nice things about using 
pyzmq for networking over other Python solutions: you can write your processing 
code very straightforwardly. You don't need to explicitly thread, either 
coorperatively or preemptively, in order interleave your processing with your 
networking.

That said, if the OP needs multiple processing threads for some reason, multiple 
processes would be appropriate.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco