Add OpenTelemetry tracing and metrics support

pkg/tracing/opentelemetry/opentelemetry_test.go

@@ -0,0 +1,67 @@
+package opentelemetry
+
+import (
+	"compress/gzip"
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	mtracing "github.com/traefik/traefik/v2/pkg/middlewares/tracing"
+	"github.com/traefik/traefik/v2/pkg/tracing"
+	"go.opentelemetry.io/collector/pdata/ptrace/ptraceotlp"
+)
+
+func TestTraceContextPropagation(t *testing.T) {
+	t.Parallel()
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gzr, err := gzip.NewReader(r.Body)
+		require.NoError(t, err)
+
+		body, err := io.ReadAll(gzr)
+		require.NoError(t, err)
+
+		req := ptraceotlp.NewExportRequest()
+		err = req.UnmarshalProto(body)
+		require.NoError(t, err)
+
+		marshalledReq, err := json.Marshal(req)
+		require.NoError(t, err)
+
+		bodyStr := string(marshalledReq)
+		assert.Regexp(t, `("traceId":"00000000000000000000000000000001")`, bodyStr)
+		assert.Regexp(t, `("parentSpanId":"0000000000000001")`, bodyStr)
+		assert.Regexp(t, `("traceState":"foo=bar")`, bodyStr)
+	}))
+	defer ts.Close()
+
+	cfg := Config{
+		Address:  strings.TrimPrefix(ts.URL, "http://"),
+		Insecure: true,
+	}
+
+	newTracing, err := tracing.NewTracing("", 0, &cfg)
+	require.NoError(t, err)
+	defer newTracing.Close()
+
+	req := httptest.NewRequest(http.MethodGet, "http://www.test.com", nil)
+	req.Header.Set("traceparent", "00-00000000000000000000000000000001-0000000000000001-00")
+	req.Header.Set("tracestate", "foo=bar")
+	rw := httptest.NewRecorder()
+
+	var forwarded bool
+	next := http.HandlerFunc(func(http.ResponseWriter, *http.Request) {
+		forwarded = true
+	})
+
+	handler := mtracing.NewEntryPoint(context.Background(), newTracing, "test", next)
+	handler.ServeHTTP(rw, req)
+
+	require.True(t, forwarded)
+}