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

Explained: CoreDNS

You deploy a new service to your Kubernetes cluster. The pods come up healthy. You open a shell inside one of them and try to reach another service by name — http://payments-service — and nothing happens. Timeout. You try the full name: http://payments-service.billing.svc.cluster.local . Still nothing. You try the service's ClusterIP directly, and it works fine. Something in the cluster is resolving names, but it's not resolving yours. If … Read More

Architecture: How Kubernetes Works

You have a fleet of containers. They need to run reliably, scale under load, recover from failures, and communicate with each other — all without you manually SSHing into servers at 2am. That's the problem Kubernetes was built to solve. This post walks through how Kubernetes is actually architected: what the pieces are, how they talk to each other, and why they were designed that way. No prior Kubernetes experience needed — just a general com… Read More