index.md

Experimental Feature: Runtime SDK (alpha)

The Runtime SDK feature provides an extensibility mechanism that allows systems, products, and services built on top of Cluster API to hook into a workload cluster’s lifecycle.

All currently implemented hooks require to also enable the ClusterClass feature. Please note that hooks are only invoked for Clusters created using ClusterClass.

Caution

Please note Runtime SDK is an advanced feature. If implemented incorrectly, a failing Runtime Extension can severely impact the Cluster API runtime.

Feature gate name: RuntimeSDK

Variable name to enable/disable the feature gate: EXP_RUNTIME_SDK

Additional documentation:

• Background information:
  • Runtime SDK CAEP
  • Topology Mutation Hook CAEP
  • Runtime Hooks for Add-on Management CAEP
• For Runtime Extension developers:
  • Implementing Runtime Extensions
  • Implementing Lifecycle Hook Extensions
  • Implementing Topology Mutation Hook Extensions
• For Cluster operators:
  • Deploying Runtime Extensions