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Building Operators with Operator SDK

Introduction

The Operator SDK is a powerful tool that simplifies the process of building Kubernetes Operators. Operators are application-specific controllers that extend the Kubernetes API to manage complex stateful applications.

Key Concepts

  • Custom Resource Definitions (CRDs): Extend Kubernetes capabilities by defining your own resource types.
  • Controllers: Watch for changes in the custom resources and manage the application state accordingly.
  • Operator Lifecycle Manager (OLM): Manages the lifecycle of your Operators and their dependencies.

Installation

To begin using the Operator SDK, you need to install it. Follow the steps below:

  1. Install kubectl if you haven't already:
    2. curl -LO "https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/darwin/amd64/kubectl"
chmod +x ./kubectl
sudo mv ./kubectl /usr/local/bin/kubectl
  2. Install the Operator SDK:
    3. curl -sSL https://github.com/operator-framework/operator-sdk/releases/latest/download/operator-sdk-v$(curl -s https://api.github.com/repos/operator-framework/operator-sdk/releases/latest | grep tag_name | cut -d '\"' -f 4)-x86_64-linux-gnu -o /usr/local/bin/operator-sdk
chmod +x /usr/local/bin/operator-sdk

Note: Ensure you have Go installed, as it is required for building Go-based operators.

Creating an Operator

Follow these key steps to create your first Operator:

  1. Initialize a new Operator project:
    2. operator-sdk init --domain=mydomain.com --repo=github.com/myusername/my-operator
  2. Create an API:
    3. operator-sdk create api --group=app --version=v1 --kind=MyApp --resource --controller
  3. Implement the reconciliation logic in controllers/myapp_controller.go.
  4. Build and push the Operator image:
    5. make docker-build docker-push IMG=
  5. Deploy the Operator:
    6. make deploy IMG=

Best Practices

  • Use CRDs to define your custom resources clearly.
  • Implement robust error handling and retries in your controllers.
  • Follow the principle of idempotency in your reconciliation logic.
  • Test your Operators thoroughly before deploying to production.

FAQ

What is an Operator?

An Operator is a method of packaging, deploying, and managing a Kubernetes application. It uses custom controllers to manage the lifecycle of specific applications.

What programming languages can I use with Operator SDK?

Operator SDK supports Go, Ansible, and Helm for building operators.

What is a Custom Resource?

A Custom Resource is an extension of the Kubernetes API that allows you to store and manage your application-specific data.