Cluster API (CAPI)

Key Takeaways for AI & Readers

• Declarative Cluster Management: Cluster API (CAPI) extends Kubernetes to manage the lifecycle of Kubernetes clusters themselves using Kubernetes-native APIs.
• Management Cluster Pattern: A dedicated "Management Cluster" is used to provision and operate multiple "Workload Clusters" across various infrastructure providers.
• Infrastructure as Code for Clusters: CAPI enables GitOps for cluster creation, configuration, and upgrades, standardizing cluster operations across different environments.
• Provider Agnostic: It provides a unified way to manage clusters on diverse platforms (AWS, Azure, GCP, VMware) through specific infrastructure providers.

Cluster API is a Kubernetes sub-project that brings declarative, Kubernetes-style APIs to cluster creation, configuration, and management. It uses the "Management Cluster" pattern.

1. Clusters Managing Clusters

Visualize a Management Cluster spawning multiple Workload Clusters across different cloud providers.

Management Cluster

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Multi-Cloud Infrastructure

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Cluster API (CAPI) allows you to manage Kubernetes clusters as if they were standard Kubernetes resources. Scaling, upgrading, and deleting clusters becomes declarative.

2. Why use CAPI?

• Standardization: Use the same YAML to create a cluster on AWS, Azure, GCP, or VMware.
• Infrastructure as Code: Since a Cluster is just a CRD, you can use ArgoCD to manage your entire fleet of Kubernetes clusters.
• Automated Upgrades: Upgrading a cluster is as simple as updating the version field in the YAML. CAPI handles the rolling update of the nodes.

3. Key Concepts

Management Cluster

The cluster where CAPI is installed. It manages the lifecycle of other clusters.

Workload Cluster

The clusters created and managed by the Management Cluster. This is where your actual apps run.

Infrastructure Provider

The cloud-specific controller (e.g., CAPA for AWS, CAPZ for Azure) that knows how to talk to the cloud API.