Granian – a Rust HTTP server for Python applications

Re:Granian – a Rust HTTP server for Python applications by WhyNotHugo on Monday January 16, 2023 @03:22PM (#34405050)

I've thought a few times of trying to write a server in Rust that runs ASGI applications. The main oddity I found is that I'd end up with two asynchronous runtimes: one for the Rust webserver, and another for the python application itself. Somehow, this never sounded right, so I never gave it a shot.

Granian sounds interesting. I'm not sure how you deal with the "two async runtimes" problem tho. Essentially, if you do non-blocking IO, then your processes start to become CPU-bound. So granian can eat up CPU on high load, and leave little CPU for the asgi application (or vice-versa). Somehow that doesn't sound right, but I also can't think of how you'd solve that.

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Re:Granian – a Rust HTTP server for Python applications by WhyNotHugo on Wednesday January 18, 2023 @08:20AM (#34426289)

Thanks for your reply! Indeed, this should still be more efficient than a pure-python approach.

My main confusion around this is: how do I scale threads? Say I have to CPU cores. Do you run one Granian thread and one python thread? I Granian under-uses CPU, Python can't use the excess. But if I run one Granian thread and two python threads, I risk Python leaving Granian with less CPU than it needs.

In practice it should not be hard to find a balance... but somehow I'm still bothered by the fact that the design has no obvious solution for this.

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