Container Runtime Interface (CRI) Support and mTLS Kubernetes Integration (with CSR)

[dciangot]

Summary

This PR introduces native Container Runtime Interface (CRI) support and Kubernetes-based mTLS certificate management, representing a major evolution in interLink's architecture and deployment capabilities.

🚀 Key Features

CRI Implementation

• Standalone CRI Binary: New cmd/interlink-cri/ with full CRI service implementation
• Direct Kubelet Integration: Native container runtime interface for seamless Kubernetes integration
• Image Management: Complete CRI image service with pull, list, and status operations
• Container Lifecycle: Full pod and container lifecycle management through CRI protocol

Kubernetes mTLS Integration

• CSR-based Certificate Management: Automated TLS certificate provisioning via Kubernetes Certificate Signing Requests
• Enhanced Security: Native Kubernetes certificate lifecycle management
• Virtual Kubelet mTLS: Client certificate support for secure plugin communication

Comprehensive Documentation

• CRI Integration Guide: Complete documentation in docs/docs/other-integrations/cri/
  • Quickstart guide for immediate deployment
  • Detailed usage guide with configuration examples
  • Technical reference with implementation details
• mTLS Deployment Guide: Step-by-step Kubernetes certificate setup
• Systemd Integration: Production deployment with systemd services

🔧 Technical Improvements

CI/CD Enhancements

• Updated Dagger CI pipeline with CRI testing support
• Enhanced build processes for new binaries
• Comprehensive integration testing

Configuration Updates

• Extended InterLink configuration for CRI support
• New certificate management options
• Enhanced plugin communication settings

🔄 Migration Path

For Existing Users:

• Backward compatible with existing Virtual Kubelet deployments
• Optional CRI integration for enhanced Kubernetes native support
• Existing plugin configurations remain supported

For New Deployments:

• CRI integration provides native kubelet experience
• Simplified certificate management through Kubernetes APIs
• Enhanced security posture with automated certificate rotation

🧪 TODO: Pre-Release Testing Coverage

• Full CRI functionality testing in CI pipeline
• mTLS certificate rotation validation
• Multi-platform compatibility verification
• Integration testing with real Kubernetes workloads

📋 Breaking Changes

• Some configuration schema updates for enhanced features
• Documentation structure reorganization
• Enhanced security defaults may require configuration updates

[dciangot]

This PR introduces substantial enhancements including native CRI support, Kubernetes mTLS integration using CSR, and improvements to CI/CD pipelines.

Pros:

• Comprehensive support for container lifecycle through CRI and integration with kubelet.
• Enhanced security with automated mTLS certificate management.
• Detailed documentation aiding deployment and migration.
• Maintains backward compatibility with existing deployments.

Suggestions:

• Consider adding automated tests specifically targeting new CRI functionalities to ensure ongoing stability.
• Verify CI/CD pipeline adjustments do not affect existing workflows adversely.

Overall, this is a significant and well-documented improvement that advances the project. Good job!

[dciangot]

Major feature PR introducing Container Runtime Interface (CRI) support and Kubernetes mTLS integration with CSR. Includes documentation and CI/CD improvements. Assigned to reviewer Bianco95. Please prioritize review for merging discussions.