Add middleware option to supply StartSpanOptions

nethttp/server.go

@@ -7,18 +7,19 @@ import (
 	"net/http"
 	"net/url"
 
-	opentracing "github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go"
 	"github.com/opentracing/opentracing-go/ext"
 )
 
 var responseSizeKey = "http.response_size"
 
 type mwOptions struct {
-	opNameFunc    func(r *http.Request) string
-	spanFilter    func(r *http.Request) bool
-	spanObserver  func(span opentracing.Span, r *http.Request)
-	urlTagFunc    func(u *url.URL) string
-	componentName string
+	opNameFunc       func(r *http.Request) string
+	spanFilter       func(r *http.Request) bool
+	startSpanOptions func(r *http.Request) []opentracing.StartSpanOption
+	spanObserver     func(span opentracing.Span, r *http.Request)
+	urlTagFunc       func(u *url.URL) string
+	componentName    string
 }
 
 // MWOption controls the behavior of the Middleware.
@@ -49,6 +50,13 @@ func MWSpanFilter(f func(r *http.Request) bool) MWOption {
 	}
 }
 
+// MWStartSpanOptions returns a MWOption that creates options for starting a span.
+func MWStartSpanOptions(f func(r *http.Request) []opentracing.StartSpanOption) MWOption {
+	return func(options *mwOptions) {
+		options.startSpanOptions = f
+	}
+}
+
 // MWSpanObserver returns a MWOption that observe the span
 // for the server-side span.
 func MWSpanObserver(f func(span opentracing.Span, r *http.Request)) MWOption {
@@ -105,8 +113,9 @@ func MiddlewareFunc(tr opentracing.Tracer, h http.HandlerFunc, options ...MWOpti
 		opNameFunc: func(r *http.Request) string {
 			return "HTTP " + r.Method
 		},
-		spanFilter:   func(r *http.Request) bool { return true },
-		spanObserver: func(span opentracing.Span, r *http.Request) {},
+		spanFilter:       func(r *http.Request) bool { return true },
+		startSpanOptions: func(r *http.Request) []opentracing.StartSpanOption { return nil },
+		spanObserver:     func(span opentracing.Span, r *http.Request) {},
 		urlTagFunc: func(u *url.URL) string {
 			return u.String()
 		},
@@ -126,7 +135,8 @@ func MiddlewareFunc(tr opentracing.Tracer, h http.HandlerFunc, options ...MWOpti
 			return
 		}
 		ctx, _ := tr.Extract(opentracing.HTTPHeaders, opentracing.HTTPHeadersCarrier(r.Header))
-		sp := tr.StartSpan(opts.opNameFunc(r), ext.RPCServerOption(ctx))
+		startSpanOptions := collectStartSpanOptions(ctx, r, opts)
+		sp := tr.StartSpan(opts.opNameFunc(r), startSpanOptions...)
 		ext.HTTPMethod.Set(sp, r.Method)
 		ext.HTTPUrl.Set(sp, opts.urlTagFunc(r.URL))
 		ext.Component.Set(sp, componentName)
@@ -164,3 +174,13 @@ func MiddlewareFunc(tr opentracing.Tracer, h http.HandlerFunc, options ...MWOpti
 	}
 	return http.HandlerFunc(fn)
 }
+
+func collectStartSpanOptions(ctx opentracing.SpanContext, r *http.Request, opts mwOptions) []opentracing.StartSpanOption {
+	mwStartSpanOptions := opts.startSpanOptions(r)
+
+	startSpanOptions := make([]opentracing.StartSpanOption, 0, len(mwStartSpanOptions)+1)
+	startSpanOptions = append(startSpanOptions, ext.RPCServerOption(ctx))
+	startSpanOptions = append(startSpanOptions, mwStartSpanOptions...)
+
+	return startSpanOptions
+}

nethttp/server_test.go

@@ -182,6 +182,81 @@ func TestSpanFilterOption(t *testing.T) {
 	}
 }
 
+func TestStartSpanOptionsOption(t *testing.T) {
+	t.Parallel()
+	mux := http.NewServeMux()
+	mux.HandleFunc("/root", func(w http.ResponseWriter, r *http.Request) {})
+
+	const customTagForHTTPMethod = "custom_tag_for_http_method"
+
+	mwOptions := []MWOption{MWStartSpanOptions(func(r *http.Request) []opentracing.StartSpanOption {
+		return []opentracing.StartSpanOption{
+			opentracing.Tag{Key: customTagForHTTPMethod, Value: r.Method},
+		}
+	})}
+
+	tests := []struct { //nolint:govet
+		name            string
+		httpMethod      string
+		options         []MWOption
+		expectMethodTag string
+	}{
+		{
+			name:            "without options",
+			httpMethod:      http.MethodGet,
+			options:         nil,
+			expectMethodTag: "<nil>",
+		},
+		{
+			name:            "with options and method = GET",
+			httpMethod:      http.MethodGet,
+			options:         mwOptions,
+			expectMethodTag: http.MethodGet,
+		},
+		{
+			name:            "with options and method = PATCH",
+			httpMethod:      http.MethodPatch,
+			options:         mwOptions,
+			expectMethodTag: http.MethodPatch,
+		},
+	}
+
+	for _, tt := range tests {
+		testCase := tt
+		t.Run(testCase.name, func(t *testing.T) {
+			t.Parallel()
+			tr := &mocktracer.MockTracer{}
+			mw := Middleware(tr, mux, testCase.options...)
+			srv := httptest.NewServer(mw)
+			defer srv.Close()
+
+			req, err := http.NewRequestWithContext(context.Background(), testCase.httpMethod, srv.URL, nil)
+			if err != nil {
+				t.Fatalf("failed to create request: %v", err)
+			}
+			client := &http.Client{}
+			resp, err := client.Do(req)
+			if err != nil {
+				t.Fatalf("server returned error: %v", err)
+			}
+			defer resp.Body.Close()
+
+			spans := tr.FinishedSpans()
+			if got, want := len(spans), 1; got != want {
+				t.Fatalf("got %d spans, expected %d", got, want)
+			}
+
+			tag, ok := spans[0].Tags()[customTagForHTTPMethod].(string)
+			if !ok {
+				tag = "<nil>"
+			}
+			if got, want := tag, testCase.expectMethodTag; got != want {
+				t.Fatalf("got %s tag name, expected %s", got, want)
+			}
+		})
+	}
+}
+
 func TestURLTagOption(t *testing.T) {
 	t.Parallel()
 	mux := http.NewServeMux()