The feedback loops behind Kubernetes

This post introduces the concept of control loops and feedback controllers, explaining how they are fundamental to Kubernetes' ability to manage workloads at scale. It details how to manually manage a PostgreSQL database, highlighting the challenges of ephemeral storage, node selection, disk management, high availability, and inter-instance communication. The post then maps these manual steps to the components of a closed feedback loop (setpoint, measured output, error, controller, actuator, plant) and explains how Kubernetes provides the necessary primitives (store, watches, queues, retries, leader election) to build robust operators for stateful systems.