Cadet

Cadet is the web application powering Source Academy.

• master is the main development branch, and may be broken, buggy, unstable, etc. It may not work with the frontend, if there are frontend changes that have not yet been merged.
• stable is the stable branch and should work with the stable branch of the frontend. Note that stable may not have stable history!

Developer setup

System requirements

1. Elixir 1.13.3+ (current version: 1.13.4)
2. Erlang/OTP 23.2.1+ (current version: 25.3.2)
3. PostgreSQL 12+ (tested to be working up to 14.5)

It is probably okay to use a different version of PostgreSQL or Erlang/OTP, but using a different version of Elixir may result in differences in e.g. mix format.

Setting up your local development environment

1. Set up the development secrets (replace the values appropriately)

   $ cp config/dev.secrets.exs.example config/dev.secrets.exs
   $ vim config/dev.secrets.exs
   

   • To use NUSNET authentication, specify the NUS ADFS OAuth2 URL. (Ask for it.) Note that the frontend will supply the ADFS client ID and redirect URL (so you will need that too, but not here).

2. Install Elixir dependencies

   $ mix deps.get
   

   If you encounter error message Fail to fetch record for 'hexpm/mime' from registry(using cache insted)The following instruction may be useful for you.

   $ mix local.hex --force
   

3. Initialise development database

   $ mix ecto.setup
   

   If you encounter error message about invalid password for the user "postgres". You should reset the "postgres" password:

   $ sudo -u postgres psql -c "ALTER USER postgres PASSWORD 'postgres';"
   

   and restart postgres service:

   $ sudo service postgresql restart
   

4. Run the server on your local machine

   $ mix phx.server
   

5. You may now make API calls to the server locally via localhost:4000. The API documentation can also be accessed at http://localhost:4000/swagger.

If you don't need to test MQTT connections for remote execution using Sling, you can stop here. Otherwise, continue to set up the local development environment with MQTT.

Setting up a local development environment with MQTT support

In addition to performing the steps above, you will need to do the following:

1. Set up a local MQTT server.

   One cross-platform solution is Mosquitto. Follow their instructions on how to install it for your system.

2. Update Mosquitto configurations

   We will require two listeners on two different ports: one for listening to the WebSockets connection from Source Academy Frontend, and one to listen for the regular MQTT connection from the EV3. Locate your mosquitto.conf file, and add the following lines:

   # Default listener
   listener 1883
   protocol mqtt
   allow_anonymous true
   
   # MQTT over WebSockets
   listener 9001
   protocol websockets
   allow_anonymous true
   

   If necessary, you can change the default port numbers, but it is generally best to stick to the default MQQT/WS ports.

3. Restart the Mosquitto service to apply configuration changes

4. Update configurations in the config/dev.secrets.exs file Scroll down to the remote_execution section near the bottom of the page, uncomment the two keys below, and update their values. Take note that the port numbers should match what you have defined earlier in mosquitto.conf.

   • endpoint_address: The address the remote device (EV3) should connect to.

     Example: "192.168.139.10:1883"

   • ws_endpoint_address: The address the frontend should connect to.

     Example: "ws://localhost:9001"

     Take note that you need to include the ws:// prefix.

   Sidenote on connecting from the EV3

   Although this value is returned to the remote device, the EV3 uses a hardcoded endpoint value, and simply discards this return value. Hence, the actual value does not matter. However, we still need to set (uncomment) endpoint_address to stop the backend from connecting to AWS.

Your backend is now all set up for remote execution using a local MQTT server. To see how to configure the EV3 to use a local MQTT server, check out the EV3-Source repository.

Obtaining access_token in dev environment

You can obtain an access_token JWT for a user with a given role by simply running:

$ mix cadet.token <role>

For more information, run

$ mix help cadet.token

Style Guide

We follow this style guide: https://github.com/lexmag/elixir-style-guide and https://github.com/christopheradams/elixir_style_guide

Where there is a conflict between the two, the first one (lexmag) shall be the one followed.

Entity-Relationship Diagram

Generated with DBeaver on 03 June 2022

License

All sources in this repository are licensed under the Apache License Version 2.