Merge pull request #36 from hobbyistlabs-coder/fix-metrics-todo-9636923013980118550

feat: Add basic metrics via expvar to health server

docs/design/ETL_TODO.md

@@ -5,7 +5,7 @@ This document tracks the tasks required to implement the "Ultimate Visibility" E
 ## 1. Extract (Ingestion & Telemetry Collection)
 
 - [ ] **Structured Logging:** Ensure `zerolog` is used consistently across the codebase for structured JSON logging. Add context to logs where missing (session IDs, tool inputs/outputs).
-- [ ] **Basic Metrics Implementation:** Introduce a metrics package (e.g., using `expvar` or a Prometheus client) to expose basic application metrics.
+- [x] **Basic Metrics Implementation:** Introduce a metrics package (e.g., using `expvar` or a Prometheus client) to expose basic application metrics.
 - [x] **Goroutine Tracking:** Implement a metric to track the number of active Goroutines.
 - [x] **Memory Tracking:** Implement a metric to track heap allocation and GC pauses.
 - [ ] **AgentLoop Telemetry:** Add specific instrumentation to the `AgentLoop` (iteration duration, tool execution duration, failure counts).

pkg/health/server.go

@@ -3,6 +3,7 @@ package health
 import (
 	"context"
 	"encoding/json"
+	"expvar"
 	"fmt"
 	"maps"
 	"net/http"
@@ -41,6 +42,7 @@ func NewServer(host string, port int) *Server {
 
 	mux.HandleFunc("/health", s.healthHandler)
 	mux.HandleFunc("/ready", s.readyHandler)
+	mux.Handle("/debug/vars", expvar.Handler())
 
 	addr := fmt.Sprintf("%s:%d", host, port)
 	s.server = &http.Server{
@@ -162,6 +164,7 @@ func (s *Server) readyHandler(w http.ResponseWriter, r *http.Request) {
 func (s *Server) RegisterOnMux(mux *http.ServeMux) {
 	mux.HandleFunc("/health", s.healthHandler)
 	mux.HandleFunc("/ready", s.readyHandler)
+	mux.Handle("/debug/vars", expvar.Handler())
 }
 
 func statusString(ok bool) string {