Kubernetes Operators

Chapter 6. Adapter Operators

Consider the numerous steps it would take to write an Operator from scratch. You would have to create CRDs to specify the interface for end users. Kubernetes controllers would not only need to be written with the Operator’s domain-specific logic, but also be correctly hooked into a running cluster to receive the proper notifications. Roles and service accounts would need to be created to permit the Operator to function in the capacity it needs. An Operator is run as a pod inside of a cluster, so an image would need to be built, along with its accompanying deployment manifest.

Many projects have already invested in application deployment and configuration technologies. The Helm project allows users to define their cluster resources in a formatted text file and deploy them through the Helm command-line tools. Ansible is a popular automation engine for creating reusable scripts for provisioning and configuring a group of resources. Both projects have devoted followings of developers who may lack the resources to migrate to using Operators for their applications.

The Operator SDK provides a solution to both these problems through its Adapter Operators. Through the command-line tool, the SDK generates the code necessary to run technologies such as Helm and Ansible in an Operator. This allows you to rapidly migrate your infrastructure to an Operator model without needing to write the necessary supporting Operator code. The advantages of doing this include: ...