Health checks

Kubernetes provides two layers of health checking. First, in the form of HTTP or TCP checks, K8s can attempt to connect to a particular endpoint and give a status of healthy on a successful connection. Second, application-specific health checks can be performed using command-line scripts.

Let's take a look at a few health checks in action. First, we'll create a new controller with a health check:

apiVersion: v1 
kind: ReplicationController 
metadata: 
  name: node-js 
  labels: 
    name: node-js 
spec: 
  replicas: 3 
  selector: 
    name: node-js 
  template: 
    metadata: 
      labels: 
        name: node-js 
    spec: 
      containers: 
      - name: node-js 
        image: jonbaier/node-express-info:latest 
        ports: 
        - containerPort: 80 
        livenessProbe: 
          # An HTTP health check  
          httpGet: 
            path: /status/ 
            port: 80 
          initialDelaySeconds: 30 
          timeoutSeconds: 1

Listing 2-7: nodejs-health-controller...