feat: The Other Dude v9.0.1 — full-featured email system

ci: add GitHub Pages deployment workflow for docs site

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

poller/internal/observability/server.go

@@ -0,0 +1,59 @@
+package observability
+
+import (
+	"context"
+	"log/slog"
+	"net/http"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// StartServer starts an HTTP server for Prometheus metrics and health checks.
+//
+// The server exposes:
+//   - GET /metrics  — Prometheus metrics endpoint
+//   - GET /health   — Liveness probe (returns 200 with {"status":"ok"})
+//
+// The server shuts down gracefully when ctx is cancelled. It runs in a
+// goroutine and does not block the caller.
+func StartServer(ctx context.Context, addr string) *http.Server {
+	mux := http.NewServeMux()
+	mux.Handle("/metrics", promhttp.Handler())
+	mux.HandleFunc("/health", healthHandler)
+
+	srv := &http.Server{
+		Addr:              addr,
+		Handler:           mux,
+		ReadHeaderTimeout: 5 * time.Second,
+	}
+
+	// Start serving in a goroutine.
+	go func() {
+		slog.Info("observability server starting", "addr", addr)
+		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			slog.Error("observability server error", "error", err)
+		}
+	}()
+
+	// Graceful shutdown when context is cancelled.
+	go func() {
+		<-ctx.Done()
+		slog.Info("observability server shutting down")
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		if err := srv.Shutdown(shutdownCtx); err != nil {
+			slog.Error("observability server shutdown error", "error", err)
+		}
+		slog.Info("observability server stopped")
+	}()
+
+	return srv
+}
+
+// healthHandler returns a simple liveness response.
+func healthHandler(w http.ResponseWriter, _ *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	_, _ = w.Write([]byte(`{"status":"ok"}`))
+}