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Updating an Existing App

This guide demonstrates how to update an application that is serving traffic to a new version. With Knative, it's easy to reroute traffic from one version of an application to another by changing the routing configuration.

A sample app is used to demonstrate the flow of updating an application, but the same principles can be applied to your own Knative application.

Before you begin

We assume you have:

Installed Knative on a Kubernetes cluster
Configured a custom domain for use with Knative

Deploying the first version

We'll be deploying an image of a demo application that displays the text "App v1" on a blue background.

First, create a new file called stage1.yamland copy this into it:

apiVersion: serving.knative.dev/v1alpha1
kind: Route
metadata:
  name: route-demo # The name of our route; appears in the URL to access the app
  namespace: default # The namespace we're working in; also appears in the URL to access the app
spec:
  traffic:
  - configurationName: route-demo-config-v1
    percent: 100 # All traffic goes to this configutation
---
apiVersion: serving.knative.dev/v1alpha1
kind: Configuration
metadata:
  name: route-demo-config-v1
  namespace: default
spec:
  revisionTemplate:
    metadata:
      labels:
        knative.dev/type: container
    spec:
      container:
        image: gcr.io/knative-samples/knative-route-demo:blue # The URL to the sample app
        imagePullPolicy: Always
        env:
          - name: T_VERSION
            value: "blue"

Save the file, then deploy the application to your cluster:

kubectl apply -f stage1.yaml

You'll now be able to view the sample app at http://route-demo.default.YOUR_CUSTOM_DOMAIN.com (replace YOUR_CUSTOM_DOMAIN) with the custom domain you configured for use with Knative.

Deploying the second version

Create a new file called stage2.yaml and copy this into it:

apiVersion: serving.knative.dev/v1alpha1
kind: Route
metadata:
  name: route-demo
  namespace: default
spec:
  traffic:
  - configurationName: route-demo-config-v1
    percent: 100
  - configurationName: route-demo-config-v2
    percent: 0
    name: v2
---
apiVersion: serving.knative.dev/v1alpha1
kind: Configuration
metadata:
  name: route-demo-config-v2
  namespace: default
spec:
  revisionTemplate:
    metadata:
      labels:
        knative.dev/type: container
    spec:
      container:
        image: gcr.io/knative-samples/knative-route-demo:green
        imagePullPolicy: Always
        env:
          - name: T_VERSION
            value: "green"

Save the file, then deploy the application to your cluster:

kubectl apply -f stage2.yaml

This deploys an image of a demo application that displays the text "App v2" on a green background.

This will only stage v2. That means:

No traffic will be routed to the v2 of the app at http://route-demo.default.YOUR_CUSTOM_DOMAIN.com
Knative creates a new route named v2 for testing the newly deployed version at http://v2.route-demo.default.YOUR_CUSTOM_DOMAIN.com

Migrating traffic to the new version

Create a new file called stage3.yaml and copy this into it:

apiVersion: serving.knative.dev/v1alpha1
kind: Route
metadata:
  name: route-demo
  namespace: default
spec:
  traffic:
  - configurationName: route-demo-config-v1
    percent: 50
  - configurationName: route-demo-config-v2
    percent: 50
    name: v2

Save the file, then deploy the updated routing configuration to your cluster:

kubectl apply -f stage3.yaml

Refresh the original route (http://route-demo.default.YOUR_CUSTOM_DOMAIN.com) a few times to show that some traffic now goes to v2 of the app.

Note, this sample shows a 50/50 split to assure you don't have to refresh too much, but it's recommended to start with 1-2% in a production environment

Reouting all traffic to the new version

Create a new file called stage4.yaml and copy this into it:

apiVersion: serving.knative.dev/v1alpha1
kind: Route
metadata:
  name: route-demo
  namespace: default
spec:
  traffic:
  - configurationName: route-demo-config-v1
    percent: 0
    name: v1
  - configurationName: route-demo-config-v2
    percent: 100