[OpenSIPS-Devel] RFC: new opensips design

[Dan Pascu]

On Friday 07 November 2008, Bogdan-Andrei Iancu wrote:
> Just to give an example: let's assume we have 1 process
>
> 1) current design:
>     time T - a message is read from network
>     t+1 - a DB is invoked
>        ---- idle ------
>     t+3 - reply from DB
>     t+4 - done with the message
>     t+5 - read the next one
>
> 2) new design
>     time T - a message is read from network (reactor gets indication
> from the network socket)
>     t+1 - a DB is invoked (context is suspended and a new socket is
> added to the reactor for waiting the DB reply)
>     t+2 - a second message is read from network (reactor gets again
> indication from the network socket)
>     t+3 - second message is done
>     t+4 - reply from DB (reactor get indication from the DB socket) -
> context is restored for the first message
>     t+5 - done with the first message

While this is a good example to show how things work, I have to make 2 
comments:

1. I know of no asynchronous database API, so in real life this cannot be 
applied to a database connection. Other mechanisms need to be employed 
with them.
2. Context switching is completely unnecessary, as long as the message you 
process is embodied in an object/structure that contains all the relevant 
information about that message. When an event happens and you get a 
notification and the associated object you just operate on it. The 
classical context switching that is necessary with multithreading or 
system processes it not needed here.

-- 
Dan