Introduction to Container Design Patterns in Kubernetes

--- title: " Container Design Patterns " date: 2016-06-21 slug: container-design-patterns url: /blog/2016/06/Container-Design-Patterns author: > Brendan Burns (Google), David Oppenheimer (Google) --- Kubernetes automates deployment, operations, and scaling of applications, but our goals in the Kubernetes project extend beyond system management -- we want Kubernetes to help developers, too. Kubernetes should make it easy for them to write the distributed applications and services that run in cloud and datacenter environments. To enable this, Kubernetes defines not only an API for administrators to perform management actions, but also an API for containerized applications to interact with the management platform. Our work on the latter is just beginning, but you can already see it manifested in a few features of Kubernetes. For example: - The “[graceful termination](/docs/api-reference/v1/definitions/#_v1_podspec)” mechanism provides a callback into the container a configurable amount of time before it is killed (due to a rolling update, node drain for maintenance, etc.). This allows the application to cleanly shut down, e.g. persist in-memory state and cleanly conclude open connections. - [Liveness and readiness probes](/docs/user-guide/production-pods/#liveness-and-readiness-probes-aka-health-checks) check a configurable application HTTP endpoint (other probe types are supported as well) to determine if the container is alive and/or ready to receive traffic. The response determines whether Kubernetes will restart the container, include it in the load-balancing pool for its Service, etc. - [ConfigMap](/docs/user-guide/configmap/) allows applications to read their configuration from a Kubernetes resource rather than using command-line flags. More generally, we see Kubernetes enabling a new generation of design patterns, similar to [object oriented design patterns](https://en.wikipedia.org/wiki/Object-oriented_programming#Design_patterns), but this time for containerized applications. That design patterns would emerge from containerized architectures is not surprising -- containers provide many of the same benefits as software objects, in terms of modularity/packaging, abstraction, and reuse. Even better, because containers generally interact with each other via HTTP and widely available data formats like JSON, the benefits can be provided in a language-independent way.

This blog post introduces the concept of container design patterns in Kubernetes, drawing parallels to object-oriented design patterns. It highlights how Kubernetes aims to assist developers in creating distributed applications by providing APIs for both management and application interaction. Features like graceful termination, liveness/readiness probes, and ConfigMap are presented as early examples of Kubernetes enabling these patterns, offering benefits like modularity, abstraction, and reuse in a language-independent manner.