Prioritize lichess API requests about heltour

[cyanfish]

I'm thinking that a true cross-process priority queue or independent lichess API worker would be fairly difficult to implement.

A simpler solution might be to use a cross-process lock on the lichess API layer, and then for low-priority requests, wait a brief period (e.g. 0.5 seconds) between calls to the API layer. That way any higher-priority requests waiting for the lock shouldn't have to worry about contention from the low-priority requests.

This assumes that there's only one thread running low-priority requests at a time, which is probably reasonable.

[lakinwecker]

Hrmm. a single-thread worker versus a single-process worker seems to be the same level of complexity. At least I don't see the savings on complexity. Also, by making it a separate process we ease some amount of deployment concerns.

Cross-process coordination is the issue, but unless we guarantee that the deployment will always be a single django process/thread (it's not currently) then we have similar issues that we have to solve anyways.

I'd be happy to discuss some thoughts on how to implement this.

[cyanfish]

I think the worker still needs to be set up on the live server, but otherwise it's implemented.