avoid duplicate tags

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

opentracing.go

@@ -94,6 +94,7 @@ type otSpan struct {
 	opts      tracer.SpanOptions
 	status    tracer.SpanStatus
 	statusMsg string
+	labels    []interface{}
 }
 
 func (os *otSpan) TraceID() string {
@@ -124,12 +125,12 @@ func (os *otSpan) Finish(opts ...tracer.SpanOption) {
 	}
 
 	l := len(options.Labels)
-	for idx := 0; idx < len(options.Labels); idx++ {
+	for idx := 0; idx < l; idx++ {
 		switch lt := options.Labels[idx].(type) {
 		case attribute.KeyValue:
 			os.span.SetTag(string(lt.Key), lt.Value.AsInterface())
 		case string:
-			if l < idx+1 {
+			if l > idx+1 {
 				os.span.SetTag(lt, options.Labels[idx+1])
 				idx++
 			}
@@ -169,18 +170,7 @@ func (os *otSpan) Kind() tracer.SpanKind {
 }
 
 func (os *otSpan) AddLabels(labels ...interface{}) {
-	l := len(labels)
+	os.labels = append(os.labels, labels...)
-	for idx := 0; idx < len(labels); idx++ {
-		switch lt := labels[idx].(type) {
-		case attribute.KeyValue:
-			os.span.SetTag(string(lt.Key), lt.Value.AsInterface())
-		case string:
-			if l < idx+1 {
-				os.span.SetTag(lt, labels[idx+1])
-				idx++
-			}
-		}
-	}
 }
 
 func NewTracer(opts ...tracer.Option) *otTracer {

opentracing_test.go

@@ -30,3 +30,24 @@ func TestTraceID(t *testing.T) {
 		t.Fatalf("invalid span span id %#+v", v)
 	}
 }
+
+func TestTraceTags(t *testing.T) {
+	md := metadata.New(1)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	ctx = metadata.NewIncomingContext(ctx, md)
+
+	mtr := mocktracer.New()
+	tr := NewTracer(Tracer(mtr))
+	if err := tr.Init(); err != nil {
+		t.Fatal(err)
+	}
+
+	var sp tracer.Span
+
+	ctx, sp = tr.Start(ctx, "test", tracer.WithSpanLabels("key", "val", "odd"))
+	sp.Finish()
+
+	msp := mtr.FinishedSpans()[0]
+	t.Logf("mock span %#+v", msp.Tags())
+}