Cassian

A Discord bot for music written in Elixir.

Table of contents

• About
• Note regarding Nostrum
• Note regarding the web part
• System requirements
• Configuration
• Up 'n' runnin'
• Deploy to Gigalixir
• Deploy to Heroku

About

The bot is written in Elixir, a functional programming language based upon Erlang. It has great performance and maintainability in live environments.

The Discord library is Nostrum, written in Elixir and supporting everything from events to voice channels.

Note regarding Nostrum

As of now the Hex release of Nostrum v0.4.6 is a bit buggy so the current version of this bot uses the nightly version of Nostrum.

Note regarding the web part

This is deprecated. It will be removed once a web app has been created because I don't want to add web functionality to the bot.

System requirements

Voice requirements

This bot needs youtube-dl and ffmpeg in order to play music. The path of them can be set with FFMPEG_PATH and YTDL_PATH accordingly. If they are not set they will fallback to /usr/bin/ffmpeg/ and /usr/bin/youtube-dl accordingly. So if your whereis <name> returns those two, you don't need to worry about them.

General bot requirements

Of course as this is written in Elixir, you will need Elixir installed. This can be easily done on Debian-based distros:

sudo apt-get install elixir

After installing Elixir you should be able to see the version:

Erlang/OTP 23 [erts-11.1.7] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe]

Elixir 1.11.2 (compiled with Erlang/OTP 23)

Try to keep the Elixir version 1.11.2 and up.

Configuration

To set the bot up-and-running you will need to set a couple of variables.

Here's the basic configuration:

use Mix.Config
config :porcelain,
  driver: Porcelain.Driver.Basic

config :nostrum,
  ffmpeg: System.get_env("FFMPEG_PATH") || "/usr/bin/ffmpeg",
  youtubedl: System.get_env("YTDL_PATH") || "/usr/bin/youtube-dl",
  token: System.get_env("DISCORD_BOT_TOKEN"),
  num_shards: :auto

config :cassian,
  prefix: System.get_env("DEFAULT_BOT_PREFIX"),
  web_enabled: System.get_env("WEB_ENABLED"),
  port: System.get_env("PORT") || "4000",
  force_ssl: System.get_env("FORCE_SSL")

Two required configs are DISCORD_BOT_TOKEN and DEFAULT_BOT_PREFIX.

Depracation warning

You can start a small plug_cowboy server via web_enabled. This is used for shields.io. If web_enabled is set to false you don't have to worry about anything below it else just set the port or use the standard 4000 one. force_ssl is there to, well, enforce SSL on request. This is meant more for services which give you certs like Heroku or Gigalixir.

Up 'n' runnin'

To start the app, once you have done everything you can just run:

Interactive console for debugging:

iex -S mix

Standard start without a console:

mix --no-halt

Deploy to Gigalixir

Gigalixir uses buildpacks just like Heroku. Currently the bot has buildpacks set and it is almost ready to be deployed. You'll just have to set a couple of variables. It's easy to set them. You can either set them via the the panel on Gigalixir or:

gigalixir config:set FFMPEG_PATH=/app/vendor/ffmpeg/ffmpeg
gigalixir config:set YTDL_PATH=/app/vendor/youtube-dl/bin/youtube-dl
gigalixir config:set DEFAULT_BOT_PREFIX=${YOUR BOT PREFIX}
gigalixir config:set DISCORD_BOT_TOKEN=${YOUR BOT TOKEN}
gigalixir config:set WEB_ENABLED=${WEB ENABLED} # If you want to use the endpoints...
gigalixir config:set FORCE_SSL=${FORCE SSL} # Make all Gigalixir request use HTTPS/SSL

After that just do:

git push gigalixir

Deploy to Heroku

Add all of the buildpacks in .buildpacks on Heroku and see Deploy to Gigalixir for the configuration. The Heroku app should automatically pick the Heroku-18 stack. If that doesn't work, just set the stack to 18 manually and the app will deploy!

And you should be up 'n' runnin'!