[receiver/datadog] Implement support for span links

.chloggen/datadog-receiver-span-links.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: datadogreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Implement support for span links
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [37449]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

receiver/datadogreceiver/README.md

@@ -58,6 +58,11 @@ https://github.com/open-telemetry/opentelemetry-collector/tree/main/config/confi
 
 - `dd.span.Resource`: The datadog resource name (as distinct from the span name)
 
+### Optional Attributes
+
+- `_dd.span_links`: This receiver supports DD Agent's `_dd.span_links` attribute for span links creation, as produced by Datadog's tracing libraries. 
+Format example can be found [here](./internal/translator/traces_translator_test.go).
+
 ### Datadog's API support
 
 **Traces**

receiver/datadogreceiver/go.mod

@@ -1,6 +1,6 @@
 module github.com/open-telemetry/opentelemetry-collector-contrib/receiver/datadogreceiver
 
-go 1.22.0
+go 1.22.7
 
 require (
 	github.com/DataDog/agent-payload/v5 v5.0.144
@@ -27,6 +27,7 @@ require (
 	go.opentelemetry.io/collector/receiver v0.119.1-0.20250210123122-44b3eeda354c
 	go.opentelemetry.io/collector/receiver/receivertest v0.119.1-0.20250210123122-44b3eeda354c
 	go.opentelemetry.io/collector/semconv v0.119.1-0.20250210123122-44b3eeda354c
+	go.opentelemetry.io/otel/trace v1.34.0
 	go.uber.org/multierr v1.11.0
 	go.uber.org/zap v1.27.0
 	google.golang.org/protobuf v1.36.5
@@ -103,14 +104,13 @@ require (
 	go.opentelemetry.io/otel/metric v1.34.0 // indirect
 	go.opentelemetry.io/otel/sdk v1.34.0 // indirect
 	go.opentelemetry.io/otel/sdk/metric v1.34.0 // indirect
-	go.opentelemetry.io/otel/trace v1.34.0 // indirect
 	go.uber.org/atomic v1.11.0 // indirect
 	golang.org/x/net v0.34.0 // indirect
 	golang.org/x/oauth2 v0.24.0 // indirect
-	golang.org/x/sys v0.29.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
 	golang.org/x/text v0.22.0 // indirect
 	golang.org/x/time v0.8.0 // indirect
-	google.golang.org/genproto/googleapis/rpc v0.0.0-20241202173237-19429a94021a // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20250115164207-1a7da9e5054f // indirect
 	google.golang.org/grpc v1.70.0 // indirect
 	gopkg.in/ini.v1 v1.67.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
@@ -125,10 +125,10 @@ retract (
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/internal/exp/metrics => ../../internal/exp/metrics
 
-replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest => ../../pkg/pdatatest
-
-replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/golden => ../../pkg/golden
-
 replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil => ../../pkg/pdatautil
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal => ../../internal/coreinternal
+
+replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/golden => ../../pkg/golden
+
+replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest => ../../pkg/pdatatest

receiver/datadogreceiver/internal/translator/traces_translator.go

@@ -20,6 +20,7 @@ import (
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/ptrace"
 	semconv "go.opentelemetry.io/collector/semconv/v1.16.0"
+	"go.opentelemetry.io/otel/trace"
 	"google.golang.org/protobuf/proto"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/datadogreceiver/internal/translator/header"
@@ -98,6 +99,8 @@ func ToTraces(payload *pb.TracerPayload, req *http.Request) ptrace.Traces {
 			}
 			newSpan := slice.AppendEmpty()
 
+			_ = tagsToSpanLinks(span.GetMeta(), newSpan.Links())
+
 			newSpan.SetTraceID(uInt64ToTraceID(0, span.TraceID))
 			newSpan.SetSpanID(uInt64ToSpanID(span.SpanID))
 			newSpan.SetStartTimestamp(pcommon.Timestamp(span.Start))
@@ -165,6 +168,57 @@ func ToTraces(payload *pb.TracerPayload, req *http.Request) ptrace.Traces {
 	return results
 }
 
+// DDSpanLink represents the structure of each JSON object
+type DDSpanLink struct {
+	TraceID    string         `json:"trace_id"`
+	SpanID     string         `json:"span_id"`
+	Tracestate string         `json:"tracestate"`
+	Attributes map[string]any `json:"attributes"`
+}
+
+func tagsToSpanLinks(tags map[string]string, dest ptrace.SpanLinkSlice) error {
+	key := "_dd.span_links"
+	val, ok := tags[key]
+	if !ok {
+		return nil
+	}
+	delete(tags, key)
+
+	var spans []DDSpanLink
+	err := json.Unmarshal([]byte(val), &spans)
+	if err != nil {
+		return err
+	}
+
+	for i := 0; i < len(spans); i++ {
+		span := spans[i]
+		link := dest.AppendEmpty()
+
+		// Convert trace id.
+		rawTrace, errTrace := trace.TraceIDFromHex(span.TraceID)
+		if errTrace != nil {
+			return errTrace
+		}
+		link.SetTraceID(pcommon.TraceID(rawTrace))
+
+		// Convert span id.
+		rawSpan, errSpan := trace.SpanIDFromHex(span.SpanID)
+		if errSpan != nil {
+			return errSpan
+		}
+		link.SetSpanID(pcommon.SpanID(rawSpan))
+
+		link.TraceState().FromRaw(span.Tracestate)
+
+		err = link.Attributes().FromRaw(span.Attributes)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 var bufferPool = sync.Pool{
 	New: func() any {
 		return new(bytes.Buffer)

receiver/datadogreceiver/internal/translator/traces_translator_test.go

@@ -38,6 +38,8 @@ var data = [2]any{
 		11: "service.name",
 		12: "1.0.1",
 		13: "version",
+		14: "_dd.span_links",
+		15: `[{"attributes":{"attr1":"val1","attr2":"val2"},"span_id":"70666bf9dee4a3fe","trace_id":"0eacdb57bebc935038bf5b4802ccabd5","tracestate":"dd=k:v"}]`,
 	},
 	1: [][][12]any{
 		{
@@ -57,6 +59,7 @@ var data = [2]any{
 					2:  3,
 					11: 6,
 					13: 12,
+					14: 15,
 				},
 				map[any]float64{
 					5: 1.2,
@@ -107,6 +110,13 @@ func TestTracePayloadV05Unmarshalling(t *testing.T) {
 	numericAttributeValue, _ := span.Attributes().Get("numeric_attribute")
 	numericAttributeFloat, _ := strconv.ParseFloat(numericAttributeValue.AsString(), 64)
 	assert.Equal(t, 1.2, numericAttributeFloat)
+
+	spanLink := span.Links().At(0)
+	assert.Equal(t, "70666bf9dee4a3fe", spanLink.SpanID().String())
+	assert.Equal(t, "0eacdb57bebc935038bf5b4802ccabd5", spanLink.TraceID().String())
+	assert.Equal(t, "dd=k:v", spanLink.TraceState().AsRaw())
+	spanLinkAttrVal, _ := spanLink.Attributes().Get("attr1")
+	assert.Equal(t, "val1", spanLinkAttrVal.Str())
 }
 
 func TestTracePayloadV07Unmarshalling(t *testing.T) {
@@ -126,7 +136,7 @@ func TestTracePayloadV07Unmarshalling(t *testing.T) {
 	translated := translatedPayloads[0]
 	span := translated.GetChunks()[0].GetSpans()[0]
 	assert.NotNil(t, span)
-	assert.Len(t, span.GetMeta(), 5, "missing attributes")
+	assert.Len(t, span.GetMeta(), 6, "missing attributes")
 	value, exists := span.GetMeta()["service.name"]
 	assert.True(t, exists, "service.name missing")
 	assert.Equal(t, "my-service", value, "service.name attribute value incorrect")
@@ -166,7 +176,7 @@ func TestTracePayloadApiV02Unmarshalling(t *testing.T) {
 		span := translated.Chunks[0].Spans[0]
 
 		assert.NotNil(t, span)
-		assert.Len(t, span.Meta, 5, "missing attributes")
+		assert.Len(t, span.Meta, 6, "missing attributes")
 		assert.Equal(t, "my-service", span.Meta["service.name"])
 		assert.Equal(t, "my-name", span.Name)
 		assert.Equal(t, "my-resource", span.Resource)