argocd-example-apps/blue-green/README.md

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 Argo Rollouts:

1. Install Argo Rollouts controller: https://github.com/argoproj/argo-rollouts#installation

2. Create a sample application and sync it.

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

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

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

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

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

   argocd 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.