Dec 042014

Just recently I’ve been looking into asynchronous programming.

Previously I had an aversion to asynchronous code due to the ugly twisted web of callback functions that it can turn into. However, after finding that having a large number of threads blocking on locks and semaphores still manages to thrash a machine, I’ve come to the conclusion that I should put aside my feelings and try it anyway.

Our codebase is written in Python 2.7, sadly, not new enough to have asyncio. However we do plan to eventually move to Python 3.x when things are a bit more stable in the Debian/Ubuntu department (Ubuntu 12.04 didn’t support it and there are a few sites that still run it, one or two still run 10.04).

That said, there’s thankfully a port of what became asyncio in the form of Trollius.

Reading through the examples though still had me lost and the documentation is not exactly extensive. In particular, coroutines and yielding. The yield operator is not new, it’s been in Python for some time, but until now I never really understood it or how it was useful in co-operative programming.

Thankfully, Sahand Saba has written a guide on how this all works:

I might put some more notes up as I learn more, but that guide explained a lot of the fundamentals behind a lot of event loop frameworks including asyncio.