blue-green

Blue Green

The blue green strategy is not supported by built-in Kubernetes Deployment but available via third-party Kubernetes controller. This example demonstrates how to implement blue-green deployment via Harness Rollouts:

1. Install Harness Rollouts controller: https://github.com/harnessproj/harness-rollouts#installation
2. Create a sample application and sync it.

harnesscd app create --name blue-green --repo https://github.com/harnessproj/harnesscd-example-apps --dest-server https://kubernetes.default.svc --dest-namespace default --path blue-green && harnesscd app sync blue-green

Once the application is synced you can access it using blue-green-helm-guestbook service.

3. Change image version parameter to trigger blue-green deployment process:

harnesscd app set blue-green -p image.tag=0.2 && harnesscd app sync blue-green

Now application runs ks-guestbook-demo:0.1 and ks-guestbook-demo:0.2 images simultaneously. The ks-guestbook-demo:0.2 is still considered blue available only via preview service blue-green-helm-guestbook-preview.

4. Promote ks-guestbook-demo:0.2 to green by patching Rollout resource:

harnesscd app patch-resource blue-green --kind Rollout --resource-name blue-green-helm-guestbook --patch '{ "status": { "verifyingPreview": false } }' --patch-type 'application/merge-patch+json'

This promotes ks-guestbook-demo:0.2 to green status and Rollout deletes old replica which runs ks-guestbook-demo:0.1.