Device & Backend

Device code runs on a raspberry pi in the cat food dispenser. The only behavior specific to the rpi/device is in hardware.js, which drives the auger motor. A fake device can be run with npm run fake.

Backend code can run anywhere, but has some requirements.

• (obviously) Needs SSL (no Heroku free dynos)
• Needs google cloud credentials to read/write datastore entities
• Needs to serve on an origin domain that matches the OAuth credentials in use
• Needs to allow websockets (no AppEngine standard)

Datastore schema

TODO: describe it

Production

Both device and backend use pm2 to manage the app. They also use nvm to install node/npm. Note that catfood/ symlink must be part of the path passed to pm2 or else it will resolve the symlink only once.

# backend
pm2 start catfood/run.sh --name catfood-backend --log $HOME/catfood.log

# device
pm2 start catfood/run.sh --name catfood-device --log $HOME/catfood.log

A free GCE f1-micro with static IPv4 address. This allows full flexibility on allowing websockets and managing SSL.

• Use nginx reverse proxy to terminate SSL. (Supports websockets!!)

  location / {
    proxy_pass      http://127.0.0.1:3000;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "Upgrade";
    proxy_set_header Host $host;
  }
  

• Use certbot to get and auto-renew LetsEncrypt certs (--nginx plugin)