This is a K8s StatefulSet autoscaler that uses the Discord's Bot endpoint to get the recommended shards configuration and automatically scale up (or down) the StatefulSet.

This project requires that you already be using Kubernetes, and assume you have some understand of how Kubernetes works.

It also assumes that you have your bot set up to handle changes in the StatefulSet's replica count gracefully. Meaning: if we scale up, all existing shards will need to re-identify with Discord to present the new shard count, and update their local cache as necessary.

It is also important that your bot accepts the following environment variables:

• SHARDS: Total shards running accross all bot instances,
• SHARD_IDS: Shard IDs handled by a bot instance, bot-0 must be handling at least shard-0,

An example speaks louder than words:

If we have 12 recommended shards and you set K8S_SHARDS_PER_BOT to 4 (default:1) then we will spin up 4 bots with SHARDS =12 and:

• bot-0's SHARD_IDS = 0-3
• bot-1's SHARD_IDS = 4-7
• bot-2's SHARD_IDS = 8-11

• Store your BOT_TOKEN in Kubernetes secret, example:

  apiVersion: v1
  kind: Secret
  metadata:
    name: bot-secrets
    namespace: develop
  type: Opaque
  data:
    bot_token: A1fva56Hf7kNakF3TVRVNE1Ut0hOzebiLllpVDJjdy5RYlBfVHlFGjJYZHd4GBM5SldLKJoKYFBHHKL=
  

• Your bot should be deployed in a statefulset and accepting SHARDS and SHARD_IDS env variables, example:

  apiVersion: apps/v1
  kind: StatefulSet
  metadata:
    name: bot
    namespace: develop
    labels:
      app: bot
  spec:
    replicas: 1
    selector:
      matchLabels:
        app: bot
    serviceName: "bot"
    template:
      metadata:
        labels:
          app: bot
      spec:
        containers:
          - name: bot
            image: gcr.io/appname/discord-bot:latest
            imagePullPolicy: "Always"
            env:
              - name: BOT_TOKEN
                valueFrom:
                  secretKeyRef:
                    name: bot-secrets
                    key: bot_token
              - name: SHARDS
                value: "1"
              - name: SHARDS_PER_BOT
                value: "1"
  

• Edit k8s/cronjob.yml and change the environment variables to match your set up

• Apply your cronjob.yml configuration to your cluster and watch the magic !