Add 'restart' endpoint to server for deploy automation

[WardBrian]

This was discussed during #253.

This lets us ping /restart with a specific secret to trigger the public server to restart. If the token is not set by the user, this endpoint never does anything.

To actually make use of this, we need to manually re-deploy after a merge, picking some secret to put into both the k8 config and this repo's production environment secrets

[WardBrian]

To test:

cd backend/
$ docker build -t stan-playground . 
$ docker run -p 8083:8080 -e SWS_RESTART_TOKEN=4321 -it stan-playground 

Then, in another window

$ curl -X POST http://localhost:8083/restart -H "Authorization: Bearer 4321"

(We should not pick 4321 for the actual token)

[magland]

Cool! But did you test restart with uvicorn?

[WardBrian]

But did you test restart with uvicorn?

What do you mean?

At the end of the curl command I posted in my comment above, the docker image exited completely, so as long as the orchestrator restarts it we should get the behavior we want

[magland]

Oh okay, uvicorn is running inside the container. Got it.

[WardBrian]

Yes, inside the image uvicorn spawns several workers. When a worker gets an authenticated restart POST, it gets the parent process id (which will be uvicorn) and sends it an interrupt. If you look at the logs while this happens, uvicorn interprets this exactly like a Ctrl+C in the terminal, and gracefully shuts down after waiting for any active jobs to finish or the timeout elapses.

Once uvicorn exits, the docker container does too

[magland]

Yes, inside the image uvicorn spawns several workers. When a worker gets an authenticated restart POST, it gets the parent process id (which will be uvicorn) and sends it an interrupt. If you look at the logs while this happens, uvicorn interprets this exactly like a Ctrl+C in the terminal, and gracefully shuts down after waiting for any active jobs to finish or the timeout elapses.

Once uvicorn exits, the docker container does too

Perfect. Seems like this is the right solution.