Cluster API is a Kubernetes sub-project focused on simplifying the creation, upgrading, and operation of Kubernetes clusters. It uses Kubernetes-style declarative APIs to manage the lifecycle of clusters, enabling infrastructure as code for Kubernetes. This allows for consistent and repeatable cluster deployments across various infrastructure providers, from on-premises data centers to public clouds. It promotes infrastructure immutability and automation for Kubernetes cluster management.
Cluster API brings the power of declarative Kubernetes-style APIs to cluster creation, configuration, and management. It treats clusters as resources, just like Pods or Services.
Key Features
- Declarative API: Manage clusters using the same
kubectlcommands and YAML manifests you use for your applications. - Infrastructure Provider Support: Extensible architecture supports major cloud providers (AWS, Azure, GCP), virtualization platforms (vSphere, OpenStack), and bare metal.
- Automated Lifecycle Management: Handles creation, scaling (up and down), upgrades (control plane and worker nodes), and deletion of clusters.
- Immutability: Promotes immutable infrastructure by replacing nodes during upgrades rather than patching them in place.
Architecture
Cluster API works by having a “Management Cluster” which hosts the CAPI controllers. These controllers watch for custom resources (like Cluster, Machine, MachineDeployment) and reconcile them against the infrastructure provider to spawn and manage “Workload Clusters”.