Support gRPC and gRPC-Web protocol in metrics

docs/content/migration/v2-to-v3.md

@@ -16,3 +16,7 @@ feature by feature, of how the configuration looked like in v2, and how it now l
 ## IPWhiteList
 
 In v3, we renamed the `IPWhiteList` middleware to `IPAllowList` without changing anything to the configuration. 
+
+## gRPC Metrics
+
+In v3, the reported status code for gRPC requests is now the value of the `Grpc-Status` header.    

pkg/middlewares/metrics/metrics.go

@@ -16,10 +16,13 @@ import (
 	"github.com/traefik/traefik/v2/pkg/middlewares/capture"
 	"github.com/traefik/traefik/v2/pkg/middlewares/retry"
 	traefiktls "github.com/traefik/traefik/v2/pkg/tls"
+	"google.golang.org/grpc/codes"
 )
 
 const (
 	protoHTTP      = "http"
+	protoGRPC      = "grpc"
+	protoGRPCWeb   = "grpc-web"
 	protoSSE       = "sse"
 	protoWebsocket = "websocket"
 	typeName       = "Metrics"
@@ -109,9 +112,12 @@ func WrapServiceHandler(ctx context.Context, registry metrics.Registry, serviceN
 }
 
 func (m *metricsMiddleware) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	proto := getRequestProtocol(req)
+
 	var labels []string
 	labels = append(labels, m.baseLabels...)
-	labels = append(labels, "method", getMethod(req), "protocol", getRequestProtocol(req))
+	labels = append(labels, "method", getMethod(req))
+	labels = append(labels, "protocol", proto)
 
 	openConnsGauge := m.openConnsGauge.With(labels...)
 	openConnsGauge.Add(1)
@@ -145,7 +151,12 @@ func (m *metricsMiddleware) ServeHTTP(rw http.ResponseWriter, req *http.Request)
 	start := time.Now()
 	next.ServeHTTP(rw, req)
 
-	labels = append(labels, "code", strconv.Itoa(capt.StatusCode()))
+	code := capt.StatusCode()
+	if proto == protoGRPC || proto == protoGRPCWeb {
+		code = grpcStatusCode(rw)
+	}
+
+	labels = append(labels, "code", strconv.Itoa(code))
 	m.reqDurationHistogram.With(labels...).ObserveFromStart(start)
 	m.reqsCounter.With(labels...).Add(1)
 	m.respsBytesCounter.With(labels...).Add(float64(capt.ResponseSize()))
@@ -158,6 +169,10 @@ func getRequestProtocol(req *http.Request) string {
 		return protoWebsocket
 	case isSSERequest(req):
 		return protoSSE
+	case isGRPCWebRequest(req):
+		return protoGRPCWeb
+	case isGRPCRequest(req):
+		return protoGRPC
 	default:
 		return protoHTTP
 	}
@@ -173,6 +188,27 @@ func isSSERequest(req *http.Request) bool {
 	return containsHeader(req, "Accept", "text/event-stream")
 }
 
+// isGRPCWebRequest determines if the specified HTTP request is a gRPC-Web request.
+func isGRPCWebRequest(req *http.Request) bool {
+	return strings.HasPrefix(req.Header.Get("Content-Type"), "application/grpc-web")
+}
+
+// isGRPCRequest determines if the specified HTTP request is a gRPC request.
+func isGRPCRequest(req *http.Request) bool {
+	return strings.HasPrefix(req.Header.Get("Content-Type"), "application/grpc")
+}
+
+// grpcStatusCode parses and returns the gRPC status code from the Grpc-Status header.
+func grpcStatusCode(rw http.ResponseWriter) int {
+	code := codes.Unknown
+	if status := rw.Header().Get("Grpc-Status"); status != "" {
+		if err := code.UnmarshalJSON([]byte(status)); err != nil {
+			return int(code)
+		}
+	}
+	return int(code)
+}
+
 func containsHeader(req *http.Request, name, value string) bool {
 	items := strings.Split(req.Header.Get(name), ",")
 	for _, item := range items {

pkg/middlewares/metrics/metrics_test.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/go-kit/kit/metrics"
 	"github.com/stretchr/testify/assert"
+	"google.golang.org/grpc/codes"
 )
 
 // CollectingCounter is a metrics.Counter implementation that enables access to the CounterValue and LastLabelValues.
@@ -129,3 +130,102 @@ func Test_getMethod(t *testing.T) {
 		})
 	}
 }
+
+func Test_getRequestProtocol(t *testing.T) {
+	testCases := []struct {
+		desc     string
+		headers  http.Header
+		expected string
+	}{
+		{
+			desc:     "default",
+			expected: protoHTTP,
+		},
+		{
+			desc: "websocket",
+			headers: http.Header{
+				"Connection": []string{"upgrade"},
+				"Upgrade":    []string{"websocket"},
+			},
+			expected: protoWebsocket,
+		},
+		{
+			desc: "SSE",
+			headers: http.Header{
+				"Accept": []string{"text/event-stream"},
+			},
+			expected: protoSSE,
+		},
+		{
+			desc: "grpc web",
+			headers: http.Header{
+				"Content-Type": []string{"application/grpc-web-text"},
+			},
+			expected: protoGRPCWeb,
+		},
+		{
+			desc: "grpc",
+			headers: http.Header{
+				"Content-Type": []string{"application/grpc-text"},
+			},
+			expected: protoGRPC,
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			req := httptest.NewRequest(http.MethodGet, "https://localhost", http.NoBody)
+			req.Header = test.headers
+
+			protocol := getRequestProtocol(req)
+
+			assert.Equal(t, test.expected, protocol)
+		})
+	}
+}
+
+func Test_grpcStatusCode(t *testing.T) {
+	testCases := []struct {
+		desc     string
+		status   string
+		expected codes.Code
+	}{
+		{
+			desc:     "invalid number",
+			status:   "foo",
+			expected: codes.Unknown,
+		},
+		{
+			desc:     "number",
+			status:   "1",
+			expected: codes.Canceled,
+		},
+		{
+			desc:     "invalid string",
+			status:   `"foo"`,
+			expected: codes.Unknown,
+		},
+		{
+			desc:     "string",
+			status:   `"OK"`,
+			expected: codes.OK,
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			rw := httptest.NewRecorder()
+			rw.Header().Set("Grpc-Status", test.status)
+
+			code := grpcStatusCode(rw)
+
+			assert.EqualValues(t, test.expected, code)
+		})
+	}
+}