feature/exporter: add Drop Counts for oltptracer's event and link

CHANGELOG.md

@@ -8,6 +8,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Changed
+
+- Add event and link drop counts to the exported data from the `oltptrace` exporter. (#2601)
+
 ## [1.4.1] - 2022-02-16
 
 ### Fixed

exporters/otlp/otlptrace/internal/tracetransform/span.go

@@ -162,9 +162,10 @@ func links(links []tracesdk.Link) []*tracepb.Span_Link {
 		sid := otLink.SpanContext.SpanID()
 
 		sl = append(sl, &tracepb.Span_Link{
-			TraceId:    tid[:],
-			SpanId:     sid[:],
-			Attributes: KeyValues(otLink.Attributes),
+			TraceId:                tid[:],
+			SpanId:                 sid[:],
+			Attributes:             KeyValues(otLink.Attributes),
+			DroppedAttributesCount: uint32(otLink.DroppedAttributeCount),
 		})
 	}
 	return sl
@@ -180,23 +181,16 @@ func spanEvents(es []tracesdk.Event) []*tracepb.Span_Event {
 	if evCount > maxEventsPerSpan {
 		evCount = maxEventsPerSpan
 	}
-	events := make([]*tracepb.Span_Event, 0, evCount)
-	nEvents := 0
+	events := make([]*tracepb.Span_Event, evCount)
 
 	// Transform message events
-	for _, e := range es {
-		if nEvents >= maxEventsPerSpan {
-			break
+	for i := 0; i < evCount; i++ {
+		events[i] = &tracepb.Span_Event{
+			Name:                   es[i].Name,
+			TimeUnixNano:           uint64(es[i].Time.UnixNano()),
+			Attributes:             KeyValues(es[i].Attributes),
+			DroppedAttributesCount: uint32(es[i].DroppedAttributeCount),
 		}
-		nEvents++
-		events = append(events,
-			&tracepb.Span_Event{
-				Name:         e.Name,
-				TimeUnixNano: uint64(e.Time.UnixNano()),
-				Attributes:   KeyValues(e.Attributes),
-				// TODO (rghetia) : Add Drop Counts when supported.
-			},
-		)
 	}
 
 	return events

exporters/otlp/otlptrace/internal/tracetransform/span_test.go

@@ -87,9 +87,10 @@ func TestSpanEvent(t *testing.T) {
 			Time:       eventTime,
 		},
 		{
-			Name:       "test 2",
-			Attributes: attrs,
-			Time:       eventTime,
+			Name:                  "test 2",
+			Attributes:            attrs,
+			Time:                  eventTime,
+			DroppedAttributeCount: 2,
 		},
 	})
 	if !assert.Len(t, got, 2) {
@@ -98,7 +99,7 @@ func TestSpanEvent(t *testing.T) {
 	eventTimestamp := uint64(1589932800 * 1e9)
 	assert.Equal(t, &tracepb.Span_Event{Name: "test 1", Attributes: nil, TimeUnixNano: eventTimestamp}, got[0])
 	// Do not test Attributes directly, just that the return value goes to the correct field.
-	assert.Equal(t, &tracepb.Span_Event{Name: "test 2", Attributes: KeyValues(attrs), TimeUnixNano: eventTimestamp}, got[1])
+	assert.Equal(t, &tracepb.Span_Event{Name: "test 2", Attributes: KeyValues(attrs), TimeUnixNano: eventTimestamp, DroppedAttributesCount: 2}, got[1])
 }
 
 func TestExcessiveSpanEvents(t *testing.T) {
@@ -124,10 +125,13 @@ func TestEmptyLinks(t *testing.T) {
 func TestLinks(t *testing.T) {
 	attrs := []attribute.KeyValue{attribute.Int("one", 1), attribute.Int("two", 2)}
 	l := []tracesdk.Link{
-		{},
 		{
-			SpanContext: trace.SpanContext{},
-			Attributes:  attrs,
+			DroppedAttributeCount: 3,
+		},
+		{
+			SpanContext:           trace.SpanContext{},
+			Attributes:            attrs,
+			DroppedAttributeCount: 3,
 		},
 	}
 	got := links(l)
@@ -139,8 +143,9 @@ func TestLinks(t *testing.T) {
 
 	// Empty should be empty.
 	expected := &tracepb.Span_Link{
-		TraceId: []uint8{0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},
-		SpanId:  []uint8{0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},
+		TraceId:                []uint8{0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},
+		SpanId:                 []uint8{0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},
+		DroppedAttributesCount: 3,
 	}
 	assert.Equal(t, expected, got[0])
 
@@ -151,6 +156,7 @@ func TestLinks(t *testing.T) {
 	// Changes to our links should not change the produced links.
 	l[1].SpanContext = l[1].SpanContext.WithTraceID(trace.TraceID{})
 	assert.Equal(t, expected, got[1])
+	assert.Equal(t, l[1].DroppedAttributeCount, int(got[1].DroppedAttributesCount))
 }
 
 func TestStatus(t *testing.T) {