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The operator provides a special deployment annotation “ab.leclouddev.com/on-delete-policy” which can be set to “destroy” or “ignore”. If it is set to “destroy” as in our example above, the operator will delete the Cloud Storage bucket when the Bucket CR is deleted, and also when the Deployment is deleted since a Deployment deletion triggers a Bucket CR deletion (use carefully as you might lose data). This is done through Kubernetes Finalizers, which I highly encourage you to read on, and you can check the full code here.
Let’s try our operator in a little demo. For this, I have created another github repository bucket-text-api which is a simple Go REST API that takes a JSON input and saves text to a Cloud Storage bucket.
The operator controller watches the Deployments and whenever it finds a Deployment with the special annotation “ab.leclouddev.com/cloud”, it will create (if missing) a matching Bucket CR. Luckily kubebuilder and controller-runtime do the heavy lifting for us here and we basically just have to define our deployment’s “Reconcile Loop”, which checks deployments and reconciles the Bucket resources:
As a big fan of automated testing, it’s comforting to learn that we can easily write tests for our controllers using envtest (which runs a local k8s control plane so we can run our tests against it), the Gingko testing framework and the Gomega matching/assertion library:
We have seen in this example how Kubernetes Operators can allow us to automate cloud infrastructure logic. But there are of course a lot more uses to operators, and you can check this list of operators in the wild.