Add stability hardening and self-heal recovery

audit/internal/webui/server.go

@@ -11,6 +11,7 @@ import (
 	"net/http"
 	"os"
 	"path/filepath"
+	"runtime/debug"
 	"sort"
 	"strconv"
 	"strings"
@@ -311,11 +312,11 @@ func NewHandler(opts HandlerOptions) http.Handler {
 	mux.HandleFunc("GET /", h.handlePage)
 
 	h.mux = mux
-	return mux
+	return recoverMiddleware(mux)
 }
 
 func (h *handler) startMetricsCollector() {
-	go func() {
+	goRecoverLoop("metrics collector", 2*time.Second, func() {
 		ticker := time.NewTicker(metricsCollectInterval)
 		defer ticker.Stop()
 		for range ticker.C {
@@ -326,7 +327,7 @@ func (h *handler) startMetricsCollector() {
 			h.feedRings(sample)
 			h.setLatestMetric(sample)
 		}
-	}()
+	})
 }
 
 func (h *handler) setLatestMetric(sample platform.LiveMetricSample) {
@@ -347,7 +348,49 @@ func (h *handler) latestMetric() (platform.LiveMetricSample, bool) {
 
 // ListenAndServe starts the HTTP server.
 func ListenAndServe(addr string, opts HandlerOptions) error {
-	return http.ListenAndServe(addr, NewHandler(opts))
+	srv := &http.Server{
+		Addr:              addr,
+		Handler:           NewHandler(opts),
+		ReadHeaderTimeout: 5 * time.Second,
+		ReadTimeout:       30 * time.Second,
+		IdleTimeout:       2 * time.Minute,
+	}
+	return srv.ListenAndServe()
+}
+
+type trackingResponseWriter struct {
+	http.ResponseWriter
+	wroteHeader bool
+}
+
+func (w *trackingResponseWriter) WriteHeader(statusCode int) {
+	w.wroteHeader = true
+	w.ResponseWriter.WriteHeader(statusCode)
+}
+
+func (w *trackingResponseWriter) Write(p []byte) (int, error) {
+	w.wroteHeader = true
+	return w.ResponseWriter.Write(p)
+}
+
+func recoverMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		tw := &trackingResponseWriter{ResponseWriter: w}
+		defer func() {
+			if rec := recover(); rec != nil {
+				slog.Error("http handler panic",
+					"method", r.Method,
+					"path", r.URL.Path,
+					"panic", fmt.Sprint(rec),
+					"stack", string(debug.Stack()),
+				)
+				if !tw.wroteHeader {
+					http.Error(tw, "internal server error", http.StatusInternalServerError)
+				}
+			}
+		}()
+		next.ServeHTTP(tw, r)
+	})
 }
 
 // ── Infrastructure handlers ──────────────────────────────────────────────────