Kubernetes Operators

Chapter 7. Operators in Go with the Operator SDK

While the Helm and Ansible Operators can be created quickly and easily, their functionality is ultimately limited by those underlying technologies. Advanced use cases, such as those that involve dynamically reacting to specific changes in the application or the cluster as a whole, require a more flexixble solution.

The Operator SDK provides that flexibility by making it easy for developers to use the Go programming language, including its ecosystem of external libraries, in their Operators.

As the process is slightly more involved than for the Helm or Ansible Operators, it makes sense to start with a summary of the high–level steps:

1. Create the necessary code that will tie in to Kubernetes and allow it to run the Operator as a controller.

2. Create one or more CRDs to model the application’s underlying business logic and provide the API for users to interact with.

3. Create a controller for each CRD to handle the lifecycle of its resources.

4. Build the Operator image and create the accompanying Kubernetes manifests to deploy the Operator and its RBAC components (service accounts, roles, etc.).

While you can write all these pieces manually, the Operator SDK provides commands that will automate the creation of much of the supporting code, allowing you to focus on implementing the actual business logic of the Operator.

This chapter uses the Operator SDK to build the project skeleton for implementing an Operator in Go (see Chapter 4 ...