ddtrace/mocktracer: update mockspan to also hold source

ddtrace/mocktracer/mockspan.go

@@ -54,6 +54,7 @@ type Span interface {
 func newSpan(t *mocktracer, operationName string, cfg *ddtrace.StartSpanConfig) *mockspan {
 	if cfg.Tags == nil {
 		cfg.Tags = make(map[string]interface{})
+		cfg.Tags[ext.Component] = "manual"
 	}
 	if cfg.Tags[ext.ResourceName] == nil {
 		cfg.Tags[ext.ResourceName] = operationName
@@ -102,6 +103,7 @@ type mockspan struct {
 	tags         map[string]interface{}
 	finishTime   time.Time
 	finished     bool
+	source       string
 
 	startTime time.Time
 	parentID  uint64
@@ -128,6 +130,9 @@ func (s *mockspan) SetTag(key string, value interface{}) {
 			s.context.setSamplingPriority(int(p))
 		}
 	}
+	if key == ext.Component {
+		s.source = value.(string)
+	}
 	s.tags[key] = value
 }
 
@@ -284,3 +289,10 @@ func (s *mockspan) Root() tracer.Span {
 	root, _ := current.(*mockspan)
 	return root
 }
+
+// Source returns the component from which the mockspan was created.
+// This is used to test the source tag of the `datadog.tracer.spans_{started,finished}`
+// health metrics.
+func (s *mockspan) Source() string {
+	return s.source
+}

ddtrace/mocktracer/mockspan_test.go

@@ -34,6 +34,7 @@ func TestNewSpan(t *testing.T) {
 		assert.NotNil(s.context)
 		assert.NotZero(s.context.spanID)
 		assert.Equal(s.context.spanID, s.context.traceID)
+		assert.Equal("manual", s.source)
 	})
 
 	t.Run("options", func(t *testing.T) {
@@ -65,6 +66,20 @@ func TestNewSpan(t *testing.T) {
 		assert.Equal(uint64(2), s.context.traceID)
 		assert.Equal(baggage, s.context.baggage)
 	})
+	t.Run("custom_source", func(t *testing.T) {
+		tr := new(mocktracer)
+		parentctx := &spanContext{spanID: 1, traceID: 2}
+		tags := make(map[string]interface{})
+		tags[ext.Component] = "sourceName"
+		opts := &ddtrace.StartSpanConfig{Parent: parentctx, Tags: tags}
+		s := newSpan(tr, "opname", opts)
+
+		assert := assert.New(t)
+		assert.NotNil(s.context)
+		assert.Equal(uint64(1), s.parentID)
+		assert.Equal(uint64(2), s.context.traceID)
+		assert.Equal("sourceName", s.Source())
+	})
 }
 
 func TestSpanSetTag(t *testing.T) {
@@ -73,7 +88,7 @@ func TestSpanSetTag(t *testing.T) {
 	s.SetTag("c", "d")
 
 	assert := assert.New(t)
-	assert.Len(s.Tags(), 3)
+	assert.Len(s.Tags(), 4)
 	assert.Equal("http.request", s.Tag(ext.ResourceName))
 	assert.Equal("b", s.Tag("a"))
 	assert.Equal("d", s.Tag("c"))
@@ -88,6 +103,14 @@ func TestSpanSetTagPriority(t *testing.T) {
 	assert.Equal(-1, s.context.samplingPriority())
 }
 
+func TestSpanSetTagComponent(t *testing.T) {
+	assert := assert.New(t)
+	s := basicSpan("http.request")
+	assert.Equal(s.Source(), "manual")
+	s.SetTag(ext.Component, "custom")
+	assert.Equal(s.Source(), "custom")
+}
+
 func TestSpanTagImmutability(t *testing.T) {
 	s := basicSpan("http.request")
 	s.SetTag("a", "b")