Custom Kubernetes controller for automating external DNS on Minecraft GameServers
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Custom Kubernetes controller for automating external DNS records for Agones Minecraft GameServers using third-party DNS providers

• controller-runtime
• Agones

You need a running GKE cluster running with Agones resources and controllers installed

• GKE

gcloud container clusters create minecraft --cluster-version=1.18 \
  --tags=mc \
  --scopes=gke-default,"https://www.googleapis.com/auth/ndev.clouddns.readwrite" \ # GKE scope needed for Cloud DNS
  --node-labels=agones-mc/<DOMAIN_NAME> \ # Replace with the domain for the zone that the controller will manage
  --num-nodes=2 \
  --no-enable-autoupgrade \
  --machine-type=n2-standard-4

gcloud config set container/cluster minecraft
gcloud container clusters get-credentials minecraft

gcloud compute firewall-rules create mc-server-firewall \
  --allow tcp:7000-8000 \
  --target-tags mc \
  --description "Firewall rule to allow mc server tcp traffic"

• Agones

kubectl create namespace agones-system
kubectl apply -f https://raw.githubusercontent.com/googleforgames/agones/release-1.13.0/install/yaml/install.yaml

kubectl apply

apiVersion: v1
kind: ServiceAccount
metadata:
  name: agones-mc-dns
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: agones-mc-dns
rules:
  - apiGroups: ['agones.dev']
    resources: ['gameservers']
    verbs: ['get', 'watch', 'list', 'update']
  - apiGroups: ['']
    resources: ['nodes']
    verbs: ['get', 'watch', 'list', 'update']
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: agones-mc-dns-viewer
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: agones-mc-dns
subjects:
  - kind: ServiceAccount
    name: agones-mc-dns
    namespace: default
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: agones-mc-dns-controller
spec:
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: agones-mc-dns-controller
  template:
    metadata:
      labels:
        app: agones-mc-dns-controller
    spec:
      serviceAccountName: agones-mc-dns
      containers:
        - name: agones-mc-dns-controller
          image: saulmaldonado/agones-mc-dns-controller
          args:
            - --zone=<MANAGED_ZONE> # Replace with name of DNS managed zone
          imagePullPolicy: Always

 docker run -it --rm --name agones-mc-dns-controller \
 -v $HOME/.kube/config:/root/.kube/config \ # Passes kubeconfig to container
 -v $HOME/.config/gcloud/:/root/.config/gcloud/ \ # Passes gcloud credentials to container
 -e HOME=/root \ # Needed for google oauth authentication
 saulmaldonado/agones-mc-dns-controller \
 --gcp-project=$(GCP_PROJECT) \ # Replace with GCP project ID
 --zone=$(MANAGED_ZONE) # Replace with Managed DNS zone

This controller takes advantage of dynamic host port allocation that Agones provisions for GameServers. Instead of creating external DNS records for Kubernetes services and ingresses, DNS A and SRV are created to point to GameServer host nodes and the their GameServer ports.

To provision an A record for Nodes, they need to have agones-mc/domain label that contains the domain of the zone that the controller is managing. This will indicate to the controller that the Node needs an A record.

Labeling existing Nodes can be done using kubectl:

kubectl label node/<NODE_NAME> agones-mc/domain=<DOMAIN>

All Nodes that you intend to host GameServers one should have this label.

A new annotation with agones-mc/externalDNS will contain the new A record that points to the Node IP.

Example:

To provision an SRV record for GameServers, they need to contain an agones-mc/domain annotation that contains the domain for the controller's Managed Zone. This will indicate to the controller that the GameServer needs a SRV record.

template:
  metadata:
    annotations:
      agones-mc/domain: <DOMAIN_NAME> # Domain name of the managed zone
      # agones-mc/externalDNS: <GAMESERVER_NAME>.<DOMAIN_NAME> # Will be added by the controller
  spec:
    containers:
      - name: mc-server
        image: itzg/minecraft-server # Minecraft server image
        imagePullPolicy: Always
        env: # Full list of ENV variables at https://github.com/itzg/docker-minecraft-server
          - name: EULA
            value: 'TRUE'

      - name: mc-monitor
        image: saulmaldonado/agones-mc-monitor # Agones monitor sidecar
        imagePullPolicy: Always

Once the pod has been created, a new SRV will be generated with the format _minecraft._tcp.<GAMESERVER_NAME>.<DOMAIN>. that points to the A record of the host Node 0 0 <PORT> <HOST_A_RECORD>.

A new annotation agones-mc/externalDNS will then be added to the GameServer containing the URL from which players can connect to.

 docker run -it --rm --name agones-mc-dns-controller \
 -v $HOME/.kube/config:/root/.kube/config \ # Passes kubeconfig to container
 -v $HOME/.config/gcloud/:/root/.config/gcloud/ \ # Passes gcloud credentials to container
 -e HOME=/root \ # Needed for google oauth authentication
 saulmaldonado/agones-mc-dns-controller \
 --gcp-project=$(GCP_PROJECT) \ # Replace with GCP project ID
 --zone=$(MANAGED_ZONE) # Replace with Managed DNS zone

Flags:

  --gcp-project string
        GCP project id
  --kubeconfig string
        Paths to a kubeconfig. Only required if out-of-cluster.
  --zone string
        DNS zone that the controller will manage

See the open issues for a list of proposed features (and known issues).

Contributions are what make the open source community such an amazing place to be learn, inspire, and create. Any contributions you make are greatly appreciated.

1. Fork the Project
2. Clone the Project
3. Create your Feature or Fix Branch (git checkout -b (feat|fix)/AmazingFeatureOrFix)
4. Commit your Changes (git commit -m 'Add some AmazingFeatureOrFix')
5. Push to the Branch (git push origin (feat|fix)/AmazingFeature)
6. Open a Pull Request

1. Clone the repo

   git clone https://github.com/saulmaldonado/agones-minecraft.git

2. Build

   make go-build

1. Clone the repo

   git clone https://github.com/saulmaldonado/agones-minecraft.git

2. Build

   docker build -t <hub-user>/agones-mc-dns-controller:latest ./controller

3. Push to Docker repo

   docker push <hub-user>/agones-mc-dns-controller:latest

Distributed under the MIT License. See LICENSE for more information.

• itzg/docker-minecraft-server

• 🐱 Github: @saulmaldonado
• 🤝 LinkedIn: @saulmaldonado4
• 🐦 Twitter: @saul_mal
• 💻 Website: saulmaldonado.com

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