[receiver/datadog][bug-fix] Add DD span metrics as attributes (open-telemetry#35087)

**Description:** <Describe what has changed.>
Datadog [divides the span's
tags](https://github.com/DataDog/dd-trace-java/blob/master/dd-trace-core/src/main/java/datadog/trace/common/writer/ddagent/TraceMapperV0_5.java#L210-L212)
into [two
fields](https://github.com/DataDog/datadog-agent/blob/1739a048156d968bbe5fd8a1ace8e07c997d16d9/pkg/proto/datadog/trace/span.proto#L50-L55),
`meta` for string values and `metrics` for numeric ones.

Currently, the receiver isn't considering the `metrics` field when
building the OTel span's attributes, losing this metadata during the
conversion. This PR fixes this issue.

**Link to tracking Issue:** <Issue number if applicable>

**Testing:** <Describe what testing was performed and which tests were
added.>

**Documentation:** <Describe the documentation added.>

---------

Co-authored-by: Sean Marciniak <[email protected]>

Author: 2 people

.chloggen/datadog-receiver-metrics-attributes-fix.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: bug_fix
+
+# 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: Fix numeric span attributes
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [35087]
+
+# (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/internal/translator/traces_translator.go

@@ -119,6 +119,11 @@ func ToTraces(payload *pb.TracerPayload, req *http.Request) ptrace.Traces {
 					newSpan.Attributes().PutStr(k, v)
 				}
 			}
+			for k, v := range span.GetMetrics() {
+				if k = translateDatadogKeyToOTel(k); len(k) > 0 {
+					newSpan.Attributes().PutDouble(k, v)
+				}
+			}
 
 			switch span.Meta[datadogSpanKindKey] {
 			case "server":

receiver/datadogreceiver/internal/translator/traces_translator_test.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"strconv"
 	"testing"
 
 	pb "github.com/DataDog/datadog-agent/pkg/proto/pbgo/trace"
@@ -28,7 +29,7 @@ var data = [2]any{
 		2:  "elasticsearch.version",
 		3:  "7.0",
 		4:  "my-name",
-		5:  "X",
+		5:  "numeric_attribute",
 		6:  "my-service",
 		7:  "my-resource",
 		8:  "_sampling_priority_v1",
@@ -86,26 +87,27 @@ func TestTracePayloadV05Unmarshalling(t *testing.T) {
 	require.NoError(t, traces.UnmarshalMsgDictionary(payload), "Must not error when marshaling content")
 	req, _ := http.NewRequest(http.MethodPost, "/v0.5/traces", io.NopCloser(bytes.NewReader(payload)))
 
-	translated := ToTraces(&pb.TracerPayload{
-		LanguageName:    req.Header.Get(header.Lang),
-		LanguageVersion: req.Header.Get(header.LangVersion),
-		TracerVersion:   req.Header.Get(header.TracerVersion),
-		Chunks:          traceChunksFromTraces(traces),
-	}, req)
+	tracePayloads, _ := HandleTracesPayload(req)
+	assert.Len(t, tracePayloads, 1, "Expected one translated payload")
+	tracePayload := tracePayloads[0]
+	translated := ToTraces(tracePayload, req)
 	assert.Equal(t, 1, translated.SpanCount(), "Span Count wrong")
 	span := translated.ResourceSpans().At(0).ScopeSpans().At(0).Spans().At(0)
 	assert.NotNil(t, span)
-	assert.Equal(t, 9, span.Attributes().Len(), "missing attributes")
+	assert.Equal(t, "my-name", span.Name())
+	assert.Equal(t, 10, span.Attributes().Len(), "missing attributes")
 	value, exists := span.Attributes().Get("service.name")
-	serviceVersionValue, _ := span.Attributes().Get("service.version")
 	assert.True(t, exists, "service.name missing")
 	assert.Equal(t, "my-service", value.AsString(), "service.name attribute value incorrect")
-	assert.Equal(t, "my-name", span.Name())
+	serviceVersionValue, _ := span.Attributes().Get("service.version")
 	assert.Equal(t, "1.0.1", serviceVersionValue.AsString())
 	spanResource, _ := span.Attributes().Get("dd.span.Resource")
 	assert.Equal(t, "my-resource", spanResource.Str())
 	spanResource1, _ := span.Attributes().Get("sampling.priority")
 	assert.Equal(t, fmt.Sprintf("%f", 1.0), spanResource1.Str())
+	numericAttributeValue, _ := span.Attributes().Get("numeric_attribute")
+	numericAttributeFloat, _ := strconv.ParseFloat(numericAttributeValue.AsString(), 64)
+	assert.Equal(t, 1.2, numericAttributeFloat)
 }
 
 func TestTracePayloadV07Unmarshalling(t *testing.T) {