My go at a Docker image

[RdJNL]

This pull request...

• [ ] Fixes a bug
• [x] Introduces a new feature
• [ ] Improves an existing feature
• [ ] Boosts code quality or performance

Description

I realize I'm not the first one to submit a Docker PR, but I'd still like to post how I've set it up.

Configuration

The configuration can be set in multiple ways with this image:

• Firstly, a config.txt file can be added in /bot-data/ or /config/ (through a volume mount or by extending from this image and adding the file to /config/). This file will be copied to the bot's directory.
• Secondly, config values can be set through environment variables. This allows one to change the settings without a config.txt file. It also means it's possible to e.g. get the bot token from a secret in Kubernetes. Any environment variable prefixed with MB- will be added to the configuration (without the prefix). So, for example, to set the token and owner, set the following environment variables:
  • MB-token=abc123
  • MB-owner=12345

Volume mounts

The serversettings.json file and playlists folder are saved to the /bot-data/ directory. It's recommended to mount this folder to some persistent storage, or the data is gonna be lost when the container is deleted. It's possible to override the playlists folder in the config, but not recommended to do so. A config.txt file can also be added to the /bot-data/ folder in order to set the configuration. It's also possible to add the config.txt file to /config/ instead, which would also require a mount.

Building the image

Right now, the Dockerfile expects there to be a JMusicBot-<version>.jar file in the docker folder for it to build. The version needs to be set using the VERSION build argument. Of course, this can be changed as needed to make it more convenient to build the image. I haven't put too much thought into this, because I'm not very familiar with Java and how to build the bot.

Basic instructions to build the image (open for improvement):

• Copy the JMusicBot-<version>.jar file to the docker folder
• Run docker build -t musicbot:latest --build-arg VERSION=0.3.5 . (change version as needed)
• To start, run: docker run -e MB-token=abc123 -e MB-owner=12345 musicbot (set the token and owner correctly)

The start example doesn't include a volume mount for /bot-data/, it's probably best to add that.

Kubernetes deployment example

An example of a Kubernetes deployment I used to run the bot

Note that the image name depends on where the image is hosted and the volume mount depends on the Kubernetes hosting situation.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: musicbot
  namespace: musicbot
  labels:
    app: musicbot
spec:
  replicas: 1
  selector:
    matchLabels:
      app: musicbot
  template:
    metadata:
      labels:
        app: musicbot
    spec:
      containers:
      - name: musicbot
        image: musicbot:latest
        env:
        - name: MB-token
          value: abc123
        - name: MB-owner
          value: '12345'
        - name: MB-game
          value: '"Listening to music"'
        - name: MB-alonetimeuntilstop
          value: '60'
        volumeMounts:
          - name: musicbot-data
            mountPath: /bot-data
        resources:
          requests:
            memory: 64Mi
            cpu: 125m
          limits:
            memory: 512Mi
            cpu: 500m
      volumes:
      - name: musicbot-data
        [...]