Minimal API implementation

[DmarshalTU]

Add HTTP API Server for Querying Events and Hooks

Summary

This PR implements a minimal read-only HTTP API server that provides RESTful endpoints for querying events, hooks, statistics, and health information. This addresses the feedback from PR #9 by implementing a generic API server that shares the same data sources as the event processor and create base line of future REST capabilities..

Context

This PR is a refactored implementation based on feedback from PR #9. Key changes from the original approach:

• ✅ Changed "sre" to "apiserver" - Generic naming for broader use cases
• ✅ Split handlers by feature set - Replaced single 1590-line file with organized handler files
• ✅ API server only, no alerting - Alerting removed for separate feature PR
• ✅ Uses AgentRef instead of AgentId - Aligned with kagent standards
• ✅ Uses concrete types - No interface{} types
• ✅ Shares same data source as processor - Real-time consistency via shared managers

Changes

Not applicable to this PR

Severity handling — I kept a default severity mapping function for the statistics endpoint (/api/v1/stats/events/summary) to provide severity breakdowns. Making it configurable requires adding a severity field to the EventConfiguration CRD schema, which is outside this PR’s scope (API server only). The current default mapping (oom-kill/node-not-ready → "critical", probe-failed/pod-restart → "warning", pod-pending → "info") need to be replaced in a future PR's that adds the optional severity field to the Hook CRD, allowing teams to customize per event type while falling back to defaults when not specified.

NotificationSuppressionDuration — Not part of API server scope (deduplication manager concern)
Database/Postgres — Using in-memory managers (appropriate for this scope)

New Components

• internal/apiserver/ - Complete API server implementation
  • server.go - Main server, routing, and middleware (228 lines)
  • events.go - Event query and streaming handlers (228 lines)
  • hooks.go - Hook configuration handlers (77 lines)
  • health.go - Health, diagnostics, and metrics handlers (162 lines)
  • stats.go - Event statistics handlers (179 lines)
  • json.go - JSON encoding utilities (14 lines)
  • swagger.go - Swagger/OpenAPI documentation (30 lines)
  • test/server_test.go - Comprehensive unit tests (334 lines, 58% coverage)

Modified Components

• cmd/main.go - Integrated API server startup with shared managers
• internal/config/config.go - Added APIServerPort configuration
• internal/interfaces/controller.go - Added GetAllHookNames() and GetEventCount() methods
• internal/workflow/coordinator.go - Updated to accept shared managers via NewCoordinatorWithManagers()

API Endpoints

Health & Diagnostics

• GET /api/v1/health - Health check endpoint
• GET /api/v1/diagnostics - Detailed diagnostics (memory, connections, event stats)
• GET /api/v1/metrics - Prometheus-style metrics

Events

• GET /api/v1/events - List events with optional filtering
  • Query parameters: namespace, eventType, resourceName, status
• GET /api/v1/events/stream - Server-Sent Events stream for real-time updates

Hooks

• GET /api/v1/hooks - List all Hook configurations

Statistics

• GET /api/v1/stats/events/summary - Event summary with counts by severity and type
• GET /api/v1/stats/events/by-type - Events grouped by type with percentages

Documentation

• GET /swagger/index.html - Swagger UI
• GET /swagger/doc.json - OpenAPI specification

Documentation

• API Documentation: Swagger/OpenAPI at /swagger/index.html

Breaking Changes

None. This is a purely additive change.

Checklist

• Code follows project style guidelines
• Self-review completed
• Comments added for complex code
• Documentation updated
• Swagger documentation generated
• All PR Feat: Embedded HTTP API Server #7 #9 feedback addressed
• No alerting features included
• Uses AgentRef throughout
• Uses concrete types (no interface{})
• Handlers split by feature set
• Shares data sources with processor

Related

• Addresses feedback from PR Feat: Embedded HTTP API Server #7 #9
• Implements requirements from issue Feat: Embedded HTTP API Server #7 (HTTP API Server)
• Follows kagent naming conventions and patterns