Rolling Out a New Version

Kubernetes Kit helps to roll out a new version of an application by sending a notification to users on the previous version so that they can choose when to switch. This allows them to save any changes to their work, rather than risk losing them.

To roll out a new version of an application, there are a few basic steps to follow. This page describes them.

Build a New Application Version

Build a new container image using Docker and tag it with the new version number. Below is an example of this:

docker build -t my-app:2.0.0 .

Note

Image Not Found by Cluster

Depending on the Kubernetes cluster you’re using, you may need to publish the image to a local registry or push the image to the cluster. Otherwise, the image will not be found. Refer to your cluster documentation for more information.

If you’re using kind on a local machine, you need to load the image to the cluster like so:

kind load docker-image my-app:2.0.0

In a production environment you can publish the image to a registry that is accessible by the cluster.

Deploy the New Version

Create a new deployment manifest:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app-v2
spec:
  replicas: 4
  selector:
    matchLabels:
      app: my-app
      version: 2.0.0
  template:
    metadata:
      labels:
        app: my-app
        version: 2.0.0
    spec:
      containers:
        - name: my-app
          image: my-app:2.0.0
          # Sets the APP_VERSION environment variable for the container which is
          # used during the version update to compare with the new version
          env:
            - name: APP_VERSION
              value: 2.0.0
          ports:
            - name: http
              containerPort: 8080
            - name: multicast
              containerPort: 5701
---
apiVersion: v1
kind: Service
metadata:
  name: my-app-v2
spec:
  selector:
    app: my-app
    version: 2.0.0
  ports:
    - name: http
      port: 80
      targetPort: http

Deploy it to the cluster like so:

kubectl apply -f app-v2.yaml

You should now see four new pods running in the cluster. Below is an example of this:

kubectl get pods

NAME                            READY   STATUS    RESTARTS      AGE
my-app-v2-5dcf4cc98c-cmb5m      1/1     Running   0             22s
my-app-v2-5dcf4cc98c-ctrxq      1/1     Running   0             22s
my-app-v2-5dcf4cc98c-ktpcq      1/1     Running   0             22s
my-app-v2-5dcf4cc98c-rfth2      1/1     Running   0             22s
my-app-v1-f87bfcbb4-5qjml       1/1     Running   0             10m
my-app-v1-f87bfcbb4-czkzr       1/1     Running   0             10m
my-app-v1-f87bfcbb4-gjqw6       1/1     Running   0             10m
my-app-v1-f87bfcbb4-rxvjb       1/1     Running   0             10m

Deploy Canary Ingress Rules

Before switching permanently to the new version, you can test access by deploying "canary" ingress rules. This routes new sessions to the new version, while keeping existing sessions on the previous version.

Create the ingress rule manifest like so:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app-canary
  annotations:
    kubernetes.io/ingress.class: "nginx"
    # --- Optional ---
    # If server Push is enabled in the application and uses Websocket for transport,
    # these settings replace the default Websocket connection timeouts in Nginx.
    nginx.ingress.kubernetes.io/proxy-send-timeout: "86400"
    nginx.ingress.kubernetes.io/proxy-read-timeout: "86400"
    # ---
    nginx.ingress.kubernetes.io/affinity: "cookie"
    # Redirects all the requests to the new version of the application
    nginx.ingress.kubernetes.io/canary: "true"
    nginx.ingress.kubernetes.io/canary-weight: "100"
spec:
  rules:
    - http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: my-app-v2
                port:
                  number: 80

Then deploy it to your cluster:

kubectl apply -f ingress-v2-canary.yaml

Notify Existing Users

Next, you may want to notify existing users. To do this, create the ingress rule manifest:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app
  annotations:
    kubernetes.io/ingress.class: "nginx"
    # --- Optional ---
    nginx.ingress.kubernetes.io/proxy-send-timeout: "86400"
    nginx.ingress.kubernetes.io/proxy-read-timeout: "86400"
    # ---
    nginx.ingress.kubernetes.io/affinity: "cookie"
    nginx.ingress.kubernetes.io/affinity-mode: "persistent"
    # Adds the X-AppUpdate new version header to the requests for the current
    # application which is used to trigger the version update notification popup
    nginx.ingress.kubernetes.io/configuration-snippet: proxy_set_header X-AppUpdate "2.0.0";
spec:
  rules:
    - http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: my-app-v1
                port:
                  number: 80

Next, deploy it to your cluster:

kubectl apply -f ingress-v1-notify.yaml

Remove Previous Version

Once you’re sure of the new version deployment, you can remove the previous version and make the ingress rules point permanently to the new version.

First, create the ingress rule manifest like this:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app
  annotations:
    kubernetes.io/ingress.class: "nginx"
    # --- Optional ---
    nginx.ingress.kubernetes.io/proxy-send-timeout: "86400"
    nginx.ingress.kubernetes.io/proxy-read-timeout: "86400"
    # ---
    nginx.ingress.kubernetes.io/affinity: "cookie"
    nginx.ingress.kubernetes.io/affinity-mode: "persistent"
spec:
  rules:
    - http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: my-app-v2
                port:
                  number: 80

Then deploy it to your cluster like so:

kubectl apply -f ingress-v2.yaml

Now delete the previous version and the canary ingress rules:

kubectl delete -f app-v1.yaml
kubectl delete -f ingress-v2-canary.yaml

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