Monthly Archives: July 2018

Threading in AC

Last time I read about threading, I read that “even experts have issues with threading.” Either that’s not very encouraging, or I’m an expert for even trying.

There are a bunch of threads and event loops in AC, and the problem of how to deal with them is inevitable. Here is an executive summary of the primary threads:

  • UI thread (managed by Qt)
    • Uses asyncio event loop, but some documentation encourages me to wrap it with QEventLoop for some unspecified reason. So far, it’s working well without using QEventLoop.
    • Core runs on the same thread using a QPygletWidget, which I assume separates resources from the main UI thread since it is OpenGL.
      • Uses QTimer for calling draw and update timers
      • Uses Pyglet’s own event loop for coordinating events within the core
  • Network thread (QThread)
    • Uses asyncio event loop, but it uses asyncio futures and ad-hoc Qt signals to communicate with the UI thread.
    • Main client handler is written using asyncio.Protocol with an async/await reactor pattern, but I want to see if I can import a Node-style event emitter library, since I was going that route anyway with the code I have written.

My fear is that the network threads will all get splintered into one thread per character session, and that Pyglet instances on the UI thread will clash, resulting in me splintering all of the Pyglet instances into their own threads. If left unchecked, I could end up with a dozen threads and a dozen event loops.

Then, we have the possibility of asset worker threads for downloading. The issue with this is possible clashing when updating the SQLite local asset repository.

The only way to properly manage all of these threads is to take my time writing clean code. I cannot rush to write code that “works” because of the risk of dozens of race conditions that bubble up, not to mention the technical debt that I incur. Still, I should not need to use a single lock if I design this correctly, due to the GIL.