Kubernetes

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Gravity can be run in Kubernetes, either as a single node or as a cluster.

Single node

For a single node instance, the Gravity container can be deployed as-is.

Note that to use DHCP when running in Kubernetes, it is recommended to deploy a DHCP on the router and have it forward requests to Gravity’s LoadBalancer IP.

See the example deployment below:

apiVersion: v1
kind: Namespace
metadata:
  name: gravity
---
apiVersion: v1
kind: Service
metadata:
  name: gravity
  namespace: gravity
  labels:
    app.kubernetes.io/name: gravity
spec:
  selector:
    app.kubernetes.io/name: gravity
  ports:
    - protocol: UDP
      port: 53
      targetPort: 53
      name: dns
    - protocol: TCP
      port: 53
      targetPort: 53
      name: dnstcp
    - port: 67
      targetPort: 67
      name: dhcp
      protocol: UDP
    - port: 69
      targetPort: 69
      name: tftp
      protocol: UDP
    - port: 8008
      targetPort: 8008
      name: http
      protocol: TCP
  type: LoadBalancer
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: gravity
  namespace: gravity
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: gravity
    spec:
      containers:
        - name: gravity
          image: ghcr.io/beryju/gravity:stable
          env:
            - name: BOOTSTRAP_ROLES
              value: dns;dhcp;api;discovery;backup;monitoring;tsdb;tftp
            - name: INSTANCE_IP
              value: <insert loadbalancer IP of gravity>
            - name: INSTANCE_LISTEN
              value: 0.0.0.0
          livenessProbe:
            httpGet:
              path: /healthz/live
              port: http-metrics
          readinessProbe:
            httpGet:
              path: /healthz/ready
              port: http-metrics
          ports:
            - containerPort: 53
              name: dns-tcp
            - containerPort: 53
              protocol: UDP
              name: dns-udp
            - containerPort: 67
              protocol: UDP
              name: dhcp
            - containerPort: 68
              protocol: UDP
              name: dhcp-alt
            - containerPort: 69
              protocol: UDP
              name: tftp
            - containerPort: 8008
              name: http
            - containerPort: 8009
              name: http-metrics
          volumeMounts:
            - name: data
              mountPath: /data
  volumeClaimTemplates:
    - metadata:
        name: data
      spec:
        accessModes: ["ReadWriteOnce"]
        resources:
          requests:
            storage: 1Gi

Multi-node cluster

When running a multi-node Gravity cluster in Kubernetes, it is recommended to not use the built-in etcd server in Gravity. This is because the built-in cluster management is optimized for static nodes and simplicity and as such doesn’t offer enough dynamic options that Kubernetes requires.

It is recommended to use either an etcd Operator like this or this, deploy etcd manually, or use Kubernetes’ etcd with Gravity.