How to Write a Kubernetes Operator

The previous post explained what a Kubernetes Operator is: a controller that watches a custom resource and continuously reconciles the actual cluster state toward the desired state. That explanation is useful. This one is different. This one ends with a working Operator. We're going to build one end-to-end: define a custom resource, write the reconciliation logic in Go, see the equivalent in Java, wire up the RBAC, and deploy it to a cluster.… Read More

Explained: Kubernetes Operators

You're deploying Kafka to Kubernetes. You write a Deployment for the brokers, a StatefulSet for ZooKeeper, ConfigMap s for configuration, Services to expose everything, and a handful of PersistentVolumeClaim s for storage. The cluster comes up. Then a broker dies and Kubernetes restarts it, but it comes back with the wrong broker ID and can't rejoin the cluster. Kubernetes did what it was told: restart the container. But it had no idea wha… Read More