Managing Kubernetes

Chapter 3. Kubernetes Architecture

Although Kubernetes is intended to make it easier to deploy and manage distributed systems, Kubernetes itself is a distributed system that needs to be managed. To be able to do that, a developer needs to have a strong understanding of the system architecture, the role of each piece in the system, and how they all fit together.

Concepts

To understand the architecture of Kubernetes, it is helpful, at first, to have a good grasp of the concepts and design principals that govern its development. Although the system can seem quite complex, it is actually based on a relatively small number of concepts that are repeated throughout. This allows Kubernetes to grow, while still remaining approachable to developers. Knowledge about one component in the system often can be directly applied to others.

Declarative Configuration

The notion of declarative configuration—when a user declares a desired state of the world to produce a result—is one of the primary drivers behind the development of Kubernetes. For example, a user might say to Kubernetes, “I want there to be five replicas of my web server running at all times.” Kubernetes, in turn, takes that declarative statement and takes responsibility for ensuring that it is true. Unfortunately, Kubernetes is unable to understand natural language instructions and so that declaration is actually in the form of a structured YAML or JSON document.

Declarative configuration differs from imperative configuration