add basic metrics for stress testing

proxy/internal/health/health.go

@@ -300,14 +300,24 @@ func NewChecker(logger *log.Logger, provider clientProvider) *Checker {
 }
 
 // NewServer creates a new health probe server.
-func NewServer(addr string, checker *Checker, logger *log.Logger) *Server {
+// If metricsHandler is non-nil, it is mounted at /metrics on the same port.
+func NewServer(addr string, checker *Checker, logger *log.Logger, metricsHandler http.Handler) *Server {
 	if logger == nil {
 		logger = log.StandardLogger()
 	}
+
+	handler := checker.Handler()
+	if metricsHandler != nil {
+		mux := http.NewServeMux()
+		mux.Handle("/metrics", metricsHandler)
+		mux.Handle("/", checker.Handler())
+		handler = mux
+	}
+
 	return &Server{
 		server: &http.Server{
 			Addr:         addr,
-			Handler:      checker.Handler(),
+			Handler:      handler,
 			ReadTimeout:  5 * time.Second,
 			WriteTimeout: 5 * time.Second,
 		},

proxy/internal/metrics/metrics.go

@@ -0,0 +1,56 @@
+package metrics
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+type Metrics struct {
+	requestsTotal   prometheus.Counter
+	requestDuration prometheus.Histogram
+	activeRequests  prometheus.Counter
+	backendDuration prometheus.Histogram
+}
+
+func New(reg prometheus.Registerer) *Metrics {
+	return &Metrics{
+		requestsTotal: promauto.With(reg).NewCounter(prometheus.CounterOpts{
+			Name: "netbird_proxy_requests_total",
+			Help: "Total number of requests made to the netbird proxy",
+		}),
+		requestDuration: promauto.With(reg).NewHistogram(prometheus.HistogramOpts{
+			Name:    "netbird_proxy_request_duration_seconds",
+			Help:    "Duration of requests made to the netbird proxy",
+			Buckets: []float64{0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10},
+		}),
+		activeRequests: promauto.With(reg).NewCounter(prometheus.CounterOpts{
+			Name: "netbird_proxy_active_requests_total",
+			Help: "Current in-flight requests handled by the netbird proxy",
+		}),
+		backendDuration: promauto.With(reg).NewHistogram(prometheus.HistogramOpts{
+			Name:    "netbird_proxy_backend_duration_seconds",
+			Help:    "Duration of peer round trip time from the netbird proxy",
+			Buckets: []float64{0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10},
+		}),
+	}
+}
+
+func (m *Metrics) Middleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		m.requestsTotal.Inc()
+		m.activeRequests.Inc()
+
+		start := time.Now()
+		next.ServeHTTP(w, r)
+
+		m.activeRequests.Desc()
+		m.requestDuration.Observe(time.Since(start).Seconds())
+	})
+}
+
+func (m *Metrics) CompleteRoundTrip(t time.Duration) {
+	m.backendDuration.Observe(t.Seconds())
+}

proxy/internal/roundtrip/netbird.go

@@ -55,6 +55,8 @@ type managementClient interface {
 	CreateProxyPeer(ctx context.Context, req *proto.CreateProxyPeerRequest, opts ...grpc.CallOption) (*proto.CreateProxyPeerResponse, error)
 }
 
+type backendMetricRecorder func(duration time.Duration)
+
 // NetBird provides an http.RoundTripper implementation
 // backed by underlying NetBird connections.
 // Clients are keyed by AccountID, allowing multiple domains to share the same connection.
@@ -70,6 +72,8 @@ type NetBird struct {
 	clients        map[types.AccountID]*clientEntry
 	initLogOnce    sync.Once
 	statusNotifier statusNotifier
+
+	recordBackendDuration backendMetricRecorder
 }
 
 // ClientDebugInfo contains debug information about a client.
@@ -375,6 +379,10 @@ func (n *NetBird) RoundTrip(req *http.Request) (*http.Response, error) {
 	resp, err := transport.RoundTrip(req)
 	duration := time.Since(start)
 
+	if n.recordBackendDuration != nil {
+		n.recordBackendDuration(duration)
+	}
+
 	if err != nil {
 		n.logger.Debugf("roundtrip: method=%s host=%s url=%s account=%s duration=%s err=%v",
 			req.Method, req.Host, req.URL.String(), accountID, duration.Truncate(time.Millisecond), err)
@@ -483,19 +491,20 @@ func (n *NetBird) ListClientsForStartup() map[types.AccountID]*embed.Client {
 // NewNetBird creates a new NetBird transport. Set wgPort to 0 for a random
 // OS-assigned port. A fixed port only works with single-account deployments;
 // multiple accounts will fail to bind the same port.
-func NewNetBird(mgmtAddr, proxyID, proxyAddr string, wgPort int, logger *log.Logger, notifier statusNotifier, mgmtClient managementClient) *NetBird {
+func NewNetBird(mgmtAddr, proxyID, proxyAddr string, wgPort int, logger *log.Logger, notifier statusNotifier, mgmtClient managementClient, metric backendMetricRecorder) *NetBird {
 	if logger == nil {
 		logger = log.StandardLogger()
 	}
 	return &NetBird{
-		mgmtAddr:       mgmtAddr,
-		proxyID:        proxyID,
-		proxyAddr:      proxyAddr,
-		wgPort:         wgPort,
-		logger:         logger,
-		clients:        make(map[types.AccountID]*clientEntry),
-		statusNotifier: notifier,
-		mgmtClient:     mgmtClient,
+		mgmtAddr:              mgmtAddr,
+		proxyID:               proxyID,
+		proxyAddr:             proxyAddr,
+		wgPort:                wgPort,
+		logger:                logger,
+		clients:               make(map[types.AccountID]*clientEntry),
+		statusNotifier:        notifier,
+		mgmtClient:            mgmtClient,
+		recordBackendDuration: metric,
 	}
 }
 

proxy/internal/roundtrip/netbird_test.go

@@ -23,7 +23,7 @@ func (m *mockMgmtClient) CreateProxyPeer(_ context.Context, _ *proto.CreateProxy
 // mockNetBird creates a NetBird instance for testing without actually connecting.
 // It uses an invalid management URL to prevent real connections.
 func mockNetBird() *NetBird {
-	return NewNetBird("http://invalid.test:9999", "test-proxy", 0, nil, nil, &mockMgmtClient{})
+	return NewNetBird("http://invalid.test:9999", "test-proxy", "localhost", 0, nil, nil, &mockMgmtClient{}, nil)
 }
 
 func TestNetBird_AddPeer_CreatesClientForNewAccount(t *testing.T) {