Add HTTP health check to the helloworld deployment

• We will take our existing helloworld deployment, and add a readiness and liveness probe healthchecks.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: helloworld-deployment
spec:
  selector:
    matchLabels:
      app: helloworld
  replicas: 1 # tells deployment to run 1 pods matching the template
  template: # create pods using pod definition in this template
    metadata:
      labels:
        app: helloworld
    spec:
      containers:
      - name: helloworld
        image: karthequian/helloworld:latest
        ports:
        - containerPort: 80

Readiness Probe

• A readiness probe is used to know when a container is ready to start accepting traffic.
• The yaml has the following parameters:

readinessProbe:
  # length of time to wait for a pod to initialize
  # after pod startup, before applying health checking
  initialDelaySeconds: 10
  # Amount of time to wait before timing out
  initialDelaySeconds: 1
  # Probe for http
  httpGet:
    # Path to probe
    path: /
    # Port to probe
    port: 80

Liveness Probe

• A liveness probe is used to know when a container might need to be restarted.
• It is used to perform periodic check on a container to make sure it is still healthy.
• A liveness probe yaml has the following parameters that need to be filled out:

livenessProbe:
  # length of time to wait for a pod to initialize
  # after pod startup, before applying health checking
  initialDelaySeconds: 10
  # Amount of time to wait before timing out
  timeoutSeconds: 1
  # Probe for http
  httpGet:
    # Path to probe
    path: /
    # Port to probe
    port: 80

• Thus, our deployment yaml now becomes:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: helloworld-deployment-with-probe
spec:
  selector:
    matchLabels:
      app: helloworld
  replicas: 1 # tells deployment to run 1 pods matching the template
  template: # create pods using pod definition in this template
    metadata:
      labels:
        app: helloworld
    spec:
      containers:
      - name: helloworld
        image: karthequian/helloworld:latest
        ports:
        - containerPort: 80
        readinessProbe:
          # length of time to wait for a pod to initialize
          # after pod startup, before applying health checking
          initialDelaySeconds: 10
          # Amount of time to wait before timing out
          initialDelaySeconds: 1
          # Probe for http
          httpGet:
            # Path to probe
            path: /
            # Port to probe
            port: 80
        livenessProbe:
          # length of time to wait for a pod to initialize
          # after pod startup, before applying health checking
          initialDelaySeconds: 10
          # Amount of time to wait before timing out
          timeoutSeconds: 1
          # Probe for http
          httpGet:
            # Path to probe
            path: /
            # Port to probe
            port: 80