Kubernetes Patterns, 2nd Edition

Chapter 11. Stateless Service

The Stateless Service pattern describes how to create and operate applications that are composed of identical ephemeral replicas. These applications are best suited for dynamic cloud environments where they can be rapidly scaled and made highly available.

Problem

The microservices architecture style is the dominant choice for implementing new greenfield cloud native applications. Among the driving principles of this architecture are things such as how it addresses a single concern, how it owns its data, how it has a well-encapsulated deployment boundary, and others. Typically, such applications also follow the twelve-factor app principles, which makes them easy to operate with Kubernetes on dynamic cloud environments.

Applying some of these principles requires understanding the business domain, identifying the service boundary, or applying domain-driven design or a similar methodology during the service implementation. Implementing some of the other principles may involve making the services ephemeral, which means the service can be created, scaled, and destroyed with no side effects. These latter concerns are easier to address when a service is stateless rather than stateful.

A stateless service does not maintain any state internally within the instance across service interactions. In our context, it means a container is stateless if it does not hold any information from requests in its internal storage (memory or temporary filesystem) that is critical ...