Removed dropped link's attributes field from API package (#2118)

* Removed DroppedAttributeCount field from Link struct

* Reintroduced DroppedAttributeCount with a wrapper struct

* Added Link type in otel/sdk package and used it instead of Trace API equivalent

* Added changelog entry

* Linting fix in changelog

* Deleted duplicated changelog section added by mistake

* Expanded changelog entry and moved it under the 'Added' section

* Explicitly mentioned otel/trace library in changelog entry under 'Removed' section to avoid ambiguity

CHANGELOG.md

@@ -15,6 +15,9 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Added the `WithRetry` option to the `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp` package.
   This option is a replacement for the removed `WithMaxAttempts` and `WithBackoff` options. (#2095)
 - Added API `LinkFromContext` to return Link which encapsulates SpanContext from provided context and also encapsulates attributes. (#2115)
+- Added a new `Link` type under the SDK `otel/sdk/trace` package that counts the number of attributes that were dropped for surpassing the `AttributePerLinkCountLimit` configured in the Span's `SpanLimits`.
+  This new type replaces the equal-named API `Link` type found in the `otel/trace` package for most usages within the SDK.
+  For example, instances of this type are now returned by the `Links()` function of `ReadOnlySpan`s provided in places like the `OnEnd` function of `SpanProcessor` implementations. (#2118)
 
 ### Changed
 
@@ -35,6 +38,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Removed the `WithMaxAttempts` and `WithBackoff` options from the `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp` package.
   The retry logic of the package has been updated to match the `otlptracegrpc` package and accordingly a `WithRetry` option is added that should be used instead. (#2095)
 - Removed metrics test package `go.opentelemetry.io/otel/sdk/export/metric/metrictest`. (#2105)
+- Removed `DroppedAttributeCount` field from `otel/trace.Link` struct. (#2118)
 
 ### Fixed
 

exporters/jaeger/jaeger_test.go

@@ -219,7 +219,7 @@ func Test_spanSnapshotToThrift(t *testing.T) {
 				Name:      "/foo",
 				StartTime: now,
 				EndTime:   now,
-				Links: []trace.Link{
+				Links: []sdktrace.Link{
 					{
 						SpanContext: trace.NewSpanContext(trace.SpanContextConfig{
 							TraceID: linkTraceID,
@@ -311,7 +311,7 @@ func Test_spanSnapshotToThrift(t *testing.T) {
 					TraceID: traceID,
 					SpanID:  parentSpanID,
 				}),
-				Links: []trace.Link{
+				Links: []sdktrace.Link{
 					{
 						SpanContext: trace.NewSpanContext(trace.SpanContextConfig{
 							TraceID: linkTraceID,

exporters/otlp/otlptrace/internal/otlptracetest/data.go

@@ -47,7 +47,7 @@ func SingleReadOnlySpan() []tracesdk.ReadOnlySpan {
 			EndTime:           time.Date(2020, time.December, 0, 20, 24, 0, 0, time.UTC),
 			Attributes:        []attribute.KeyValue{},
 			Events:            []tracesdk.Event{},
-			Links:             []trace.Link{},
+			Links:             []tracesdk.Link{},
 			Status:            tracesdk.Status{Code: codes.Ok},
 			DroppedAttributes: 0,
 			DroppedEvents:     0,

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

@@ -146,7 +146,7 @@ func status(status codes.Code, message string) *tracepb.Status {
 }
 
 // links transforms span Links to OTLP span links.
-func links(links []trace.Link) []*tracepb.Span_Link {
+func links(links []tracesdk.Link) []*tracepb.Span_Link {
 	if len(links) == 0 {
 		return nil
 	}

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

@@ -120,12 +120,12 @@ func TestNilLinks(t *testing.T) {
 }
 
 func TestEmptyLinks(t *testing.T) {
-	assert.Nil(t, links([]trace.Link{}))
+	assert.Nil(t, links([]tracesdk.Link{}))
 }
 
 func TestLinks(t *testing.T) {
 	attrs := []attribute.KeyValue{attribute.Int("one", 1), attribute.Int("two", 2)}
-	l := []trace.Link{
+	l := []tracesdk.Link{
 		{},
 		{
 			SpanContext: trace.SpanContext{},
@@ -234,7 +234,7 @@ func TestSpanData(t *testing.T) {
 				},
 			},
 		},
-		Links: []trace.Link{
+		Links: []tracesdk.Link{
 			{
 				SpanContext: trace.NewSpanContext(trace.SpanContextConfig{
 					TraceID:    trace.TraceID{0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF},
@@ -244,6 +244,7 @@ func TestSpanData(t *testing.T) {
 				Attributes: []attribute.KeyValue{
 					attribute.String("LinkType", "Parent"),
 				},
+				DroppedAttributeCount: 0,
 			},
 			{
 				SpanContext: trace.NewSpanContext(trace.SpanContextConfig{
@@ -254,6 +255,7 @@ func TestSpanData(t *testing.T) {
 				Attributes: []attribute.KeyValue{
 					attribute.String("LinkType", "Child"),
 				},
+				DroppedAttributeCount: 0,
 			},
 		},
 		Status: tracesdk.Status{

sdk/trace/link.go

@@ -0,0 +1,34 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace // import "go.opentelemetry.io/otel/sdk/trace"
+
+import (
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// Link is the relationship between two Spans. The relationship can be within
+// the same Trace or across different Traces.
+type Link struct {
+	// SpanContext of the linked Span.
+	SpanContext trace.SpanContext
+
+	// Attributes describe the aspects of the link.
+	Attributes []attribute.KeyValue
+
+	// DroppedAttributeCount is the number of attributes that were not
+	// recorded due to configured limits being reached.
+	DroppedAttributeCount int
+}

sdk/trace/snapshot.go

@@ -34,7 +34,7 @@ type snapshot struct {
 	endTime                time.Time
 	attributes             []attribute.KeyValue
 	events                 []Event
-	links                  []trace.Link
+	links                  []Link
 	status                 Status
 	childSpanCount         int
 	droppedAttributeCount  int
@@ -87,7 +87,7 @@ func (s snapshot) Attributes() []attribute.KeyValue {
 }
 
 // Links returns all the links the span has to other spans.
-func (s snapshot) Links() []trace.Link {
+func (s snapshot) Links() []Link {
 	return s.links
 }
 

sdk/trace/span.go

@@ -55,7 +55,7 @@ type ReadOnlySpan interface {
 	// Attributes returns the defining attributes of the span.
 	Attributes() []attribute.KeyValue
 	// Links returns all the links the span has to other spans.
-	Links() []trace.Link
+	Links() []Link
 	// Events returns all the events that occurred within in the spans
 	// lifetime.
 	Events() []Event
@@ -386,11 +386,11 @@ func (s *span) Attributes() []attribute.KeyValue {
 }
 
 // Links returns the links of this span.
-func (s *span) Links() []trace.Link {
+func (s *span) Links() []Link {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	if len(s.links.queue) == 0 {
-		return []trace.Link{}
+		return []Link{}
 	}
 	return s.interfaceArrayToLinksArray()
 }
@@ -435,13 +435,15 @@ func (s *span) addLink(link trace.Link) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
+	var droppedAttributeCount int
+
 	// Discard over limited attributes
 	if len(link.Attributes) > s.spanLimits.AttributePerLinkCountLimit {
-		link.DroppedAttributeCount = len(link.Attributes) - s.spanLimits.AttributePerLinkCountLimit
+		droppedAttributeCount = len(link.Attributes) - s.spanLimits.AttributePerLinkCountLimit
 		link.Attributes = link.Attributes[:s.spanLimits.AttributePerLinkCountLimit]
 	}
 
-	s.links.add(link)
+	s.links.add(Link{link.SpanContext, link.Attributes, droppedAttributeCount})
 }
 
 // DroppedAttributes returns the number of attributes dropped by the span
@@ -514,10 +516,10 @@ func (s *span) snapshot() ReadOnlySpan {
 	return &sd
 }
 
-func (s *span) interfaceArrayToLinksArray() []trace.Link {
-	linkArr := make([]trace.Link, 0)
+func (s *span) interfaceArrayToLinksArray() []Link {
+	linkArr := make([]Link, 0)
 	for _, value := range s.links.queue {
-		linkArr = append(linkArr, value.(trace.Link))
+		linkArr = append(linkArr, value.(Link))
 	}
 	return linkArr
 }

sdk/trace/trace_test.go

@@ -656,10 +656,10 @@ func TestLinks(t *testing.T) {
 	sc1 := trace.NewSpanContext(trace.SpanContextConfig{TraceID: trace.TraceID([16]byte{1, 1}), SpanID: trace.SpanID{3}})
 	sc2 := trace.NewSpanContext(trace.SpanContextConfig{TraceID: trace.TraceID([16]byte{1, 1}), SpanID: trace.SpanID{3}})
 
-	links := []trace.Link{
-		{SpanContext: sc1, Attributes: []attribute.KeyValue{k1v1}},
-		{SpanContext: sc2, Attributes: []attribute.KeyValue{k2v2, k3v3}},
-	}
+	l1 := trace.Link{SpanContext: sc1, Attributes: []attribute.KeyValue{k1v1}}
+	l2 := trace.Link{SpanContext: sc2, Attributes: []attribute.KeyValue{k2v2, k3v3}}
+
+	links := []trace.Link{l1, l2}
 	span := startSpan(tp, "Links", trace.WithLinks(links...))
 
 	got, err := endSpan(te, span)
@@ -674,7 +674,7 @@ func TestLinks(t *testing.T) {
 		}),
 		parent:                 sc.WithRemote(true),
 		name:                   "span0",
-		links:                  links,
+		links:                  []Link{{l1.SpanContext, l1.Attributes, 0}, {l2.SpanContext, l2.Attributes, 0}},
 		spanKind:               trace.SpanKindInternal,
 		instrumentationLibrary: instrumentation.Library{Name: "Links"},
 	}
@@ -715,9 +715,9 @@ func TestLinksOverLimit(t *testing.T) {
 		}),
 		parent: sc.WithRemote(true),
 		name:   "span0",
-		links: []trace.Link{
-			{SpanContext: sc2, Attributes: []attribute.KeyValue{k2v2}},
-			{SpanContext: sc3, Attributes: []attribute.KeyValue{k3v3}},
+		links: []Link{
+			{SpanContext: sc2, Attributes: []attribute.KeyValue{k2v2}, DroppedAttributeCount: 0},
+			{SpanContext: sc3, Attributes: []attribute.KeyValue{k3v3}, DroppedAttributeCount: 0},
 		},
 		droppedLinkCount:       1,
 		spanKind:               trace.SpanKindInternal,
@@ -1585,7 +1585,7 @@ func TestAddLinksWithMoreAttributesThanLimit(t *testing.T) {
 		}),
 		parent: sc.WithRemote(true),
 		name:   "span0",
-		links: []trace.Link{
+		links: []Link{
 			{
 				SpanContext:           sc1,
 				Attributes:            []attribute.KeyValue{k1v1},

sdk/trace/tracetest/span.go

@@ -63,7 +63,7 @@ type SpanStub struct {
 	EndTime                time.Time
 	Attributes             []attribute.KeyValue
 	Events                 []tracesdk.Event
-	Links                  []trace.Link
+	Links                  []tracesdk.Link
 	Status                 tracesdk.Status
 	DroppedAttributes      int
 	DroppedEvents          int
@@ -133,7 +133,7 @@ type spanSnapshot struct {
 	endTime                time.Time
 	attributes             []attribute.KeyValue
 	events                 []tracesdk.Event
-	links                  []trace.Link
+	links                  []tracesdk.Link
 	status                 tracesdk.Status
 	droppedAttributes      int
 	droppedEvents          int
@@ -150,7 +150,7 @@ func (s spanSnapshot) SpanKind() trace.SpanKind         { return s.spanKind }
 func (s spanSnapshot) StartTime() time.Time             { return s.startTime }
 func (s spanSnapshot) EndTime() time.Time               { return s.endTime }
 func (s spanSnapshot) Attributes() []attribute.KeyValue { return s.attributes }
-func (s spanSnapshot) Links() []trace.Link              { return s.links }
+func (s spanSnapshot) Links() []tracesdk.Link           { return s.links }
 func (s spanSnapshot) Events() []tracesdk.Event         { return s.events }
 func (s spanSnapshot) Status() tracesdk.Status          { return s.status }
 func (s spanSnapshot) DroppedAttributes() int           { return s.droppedAttributes }

trace/trace.go

@@ -402,10 +402,6 @@ type Link struct {
 
 	// Attributes describe the aspects of the link.
 	Attributes []attribute.KeyValue
-
-	// DroppedAttributeCount is the number of attributes that were not
-	// recorded due to configured limits being reached.
-	DroppedAttributeCount int
 }
 
 // LinkFromContext returns a link encapsulating the SpanContext in the provided ctx.