Kustomize Transformers

In this repository you can found an use case of Kustomize Transformers in action to deploy an application using ArgoCD with a Blue/Green strategy.

NOTE: for more information about transformers you can see next link: https://kubectl.docs.kubernetes.io/references/kustomize/kustomization/. And you can check the file openshift/overlays/prod/blue/kustomization.yaml to see two key concepts.

Pre-requisites

To replicate this exercise you need:

• A kubernetes/openshift cluster
• A running instance of ArgoCD
• This repository

How to use it?

1. Open the ArgoCD web console and create the blue application first. For this, complete the form with the next values:

   • Application Name: argocolors-app-prod-blue
   • Project Name: default
   • Sync Policy: Automatic
   • Marked Options:
     • Apply Out Of Sync Only
   • Repository URL: https://github.com/lozanotux/kustomize-transformers.git
   • Revision: main
   • Path: openshift/overlays/prod/blue
   • Cluster URL: https://kubernetes.default.svc
   • Namespace: Choose your own namespace

2. Repeat the previous step, but create the green application instead. Complete the form with the next values:

   • Application Name: argocolors-app-prod-green
   • Project Name: default
   • Sync Policy: Automatic
   • Marked Options:
     • Apply Out Of Sync Only
   • Repository URL: https://github.com/lozanotux/kustomize-transformers.git
   • Revision: main
   • Path: openshift/overlays/prod/green
   • Cluster URL: https://kubernetes.default.svc
   • Namespace: Choose your own namespace

3. Then, is time to create the Route of the application. Maybe, in a CI/CD scenario this can achieved with a Tekton Task instead of manually. So, run the next oc command from a command line:

   $ oc create route edge argocolors-app-bluegreen --service=argocolors-app-blue

   NOTE: you can now open the resulting URL in a web browser to see argocolors-app in action. To know wich is the resulting URL you can run the next command: oc get route argocolors-app-bluegreen -o template --template=https://{{.spec.host}}

4. To change from blue to green application version, you can edit your Route object to point to corresponding service. To do this with oc tool, you can the next command:

   $ oc set route-backends argocolors-app-bluegreen argocolors-app-green=100

   NOTE: to revert the changes, simply modify the name of the service at the end of the command.