feat: add kubectl plugin for diagnosing kgateway policies

[MayorFaj]

Description

CLI-Based Policy Diagnostics Enhancement

Summary

This proposal addresses the issue where TrafficPolicy resources that reference non-existing targets do not provide clear status information or logging to help users diagnose attachment problems. We propose building CLI diagnostic capabilities to provide comprehensive policy analysis and troubleshooting tools.

Motivation

Current Problems

1. Poor Visibility: Users have limited insight into why policies aren't working as expected
2. Debugging Difficulty: No systematic way to analyze policy attachment issues across the cluster

Goals

• Provide immediate diagnostic feedback for policy attachment issues
• Enable proactive identification of configuration problems
• Support both development and production troubleshooting workflows
• Integrate seamlessly with existing kubectl workflows

Proposal

CLI-First Approach

Rather than expanding the Status API or adding complex controller logging, we propose enhancing the existing CLI diagnostic capabilities as the primary mechanism for policy troubleshooting.

Rationale

1. Immediate Feedback: CLI tools provide instant analysis without waiting for controller reconciliation
2. Rich Output: Can provide detailed explanations and remediation suggestions
3. Flexible Deployment: Works in any environment with kubectl access
4. CI/CD Integration: Easy to integrate into deployment pipelines for validation

Implementation Strategy

1. Enhanced kubectl Plugin

Build the kubectl-kgateway plugin with comprehensive diagnostic capabilities:

# Analyze specific policy
kubectl kgateway policy gw-policy -n kgateway-test

# Analyze all policies in namespace
kubectl kgateway policy -n production

# Cluster-wide analysis
kubectl kgateway policy --all-namespaces

2. Core Diagnostic Features

Policy Status Analysis:

• Attachment status (attached/unattached)
• Ancestor reference validation
• Target reference existence checks
• Target selector matching analysis

Target Resource Validation:

• Verify target resources exist
• Check parent reference chains (HTTPRoute → Gateway)
• Validate resource relationships

Common Issues Detection:

• Empty target references/selectors
• Misconfigured label selectors
• Missing parent resources
• Cross-namespace reference issues

Advantages Over Alternatives

vs. Enhanced Status API

• Immediate availability: No controller changes required
• Rich formatting: Better user experience than structured status
• Backward compatibility: No API changes needed

vs. Controller Logging

• Targeted analysis: On-demand rather than constant logging
• User-friendly: Structured output vs. log parsing
• Remediation guidance: Actionable suggestions

vs. New CRDs/Controllers

• Simplicity: Leverages existing resources
• Performance: No additional cluster resources
• Maintainability: Simpler implementation and testing

Change Type

/kind feature

Changelog

None

Additional Notes

[MayorFaj]

@shashankram @ymesika your input is required and appreciated, thanks