Node Readiness Controller

A Kubernetes controller that provides fine-grained, declarative readiness for nodes. It ensures nodes only accept workloads when all required components eg: network agents, GPU drivers, storage drivers or custom health-checks, are fully ready on the node.

This project implements the proposed NodeReadinessGates API (KEP 5233) as an out-of-band solution and brings it to any Kubernetes cluster.

Use it to orchestrate complex bootstrap steps in your node-init workflow, enforce node health and improve workload reliability.

What is Node Readiness Controller?

The Node Readiness Controller extends Kubernetes' node readiness model by allowing you to define additional pre-requisites for nodes (as readiness rules) in node conditions. It automatically manages node taints to prevent scheduling until all specified conditions are satisfied.

Why This Project?

Kubernetes node has a simple "Ready" condition. Modern workloads need more critical infrastructure dependencies before they can run.

With this controller you can:

• Define custom readiness for your workload
• Automatically taint and untaint nodes
• Support continuous readiness enforcement to block scheduling for fuse break scenarios
• Integrate with existing problem-detectors like NPD or any custom daemons / node plugins for reporting readiness

Key Features

• Multi-condition Rules: Define rules with flexible condition policies (allOf or anyOf) to require ALL or ANY specified conditions to be satisfied
• Flexible Enforcement: Support for bootstrap-only and continuous enforcement modes
• Conflict Prevention: Validation webhook prevents conflicting taint configurations
• Dry Run Mode: Preview rule impact before applying changes
• Comprehensive Status: Detailed observability into rule evaluation and node readiness status
• Node Targeting: Use label selectors to target specific node types
• Bootstrap Completion Tracking: Prevents re-evaluation once bootstrap conditions are met

Demo

Node Readiness Controller in Kind cluster

!Node Readiness Demo

Example Rule

apiVersion: readiness.node.x-k8s.io/v1alpha1
kind: NodeReadinessRule
metadata:
  name: network-readiness-rule
spec:
  conditions:
    - type: "example.com/CNIReady"
      requiredStatus: "True"
  taint:
    key: "readiness.k8s.io/NetworkReady"
    effect: "NoSchedule"
    value: "pending"
  enforcementMode: "bootstrap-only"
  nodeSelector:
    matchLabels:
      node-role.kubernetes.io/worker: ""

Find a more detailed walkthrough of setting up Node Readiness Controller in your Kind cluster here.

High-level Roadmap

• [X] Release v0.1.0
• [X] Add documentation capturing design details
• [X] Metrics and alerting integration
• [X] Validation Webhook for rules
• [ ] Improve logging and add debugging pointers
• [ ] Performance optimizations for large clusters
• [ ] Scale testing 1000+ nodes

Getting Involved

If you're interested in participating in future discussions or development related to Node Readiness Controller, you can reach the maintainers of the project at:

• Slack: #sig-node-readiness-controller. (visit slack.k8s.io for a workspace invitation)

• Issues: GitHub Issues
• Discussions: GitHub Discussions

Code of conduct

Participation in the Kubernetes community is governed by the Kubernetes Code of Conduct.