feat: add process tags to tracing payloads

ddtrace/tracer/span.go

@@ -963,6 +963,8 @@ const (
 	keyPeerServiceRemappedFrom = "_dd.peer.service.remapped_from"
 	// keyBaseService contains the globally configured tracer service name. It is only set for spans that override it.
 	keyBaseService = "_dd.base_service"
+	// keyProcessTags contains a list of process tags to indentify the service.
+	keyProcessTags = "_dd.tags.process"
 )
 
 // The following set of tags is used for user monitoring and set through calls to span.SetUser().

ddtrace/tracer/spancontext.go

@@ -20,6 +20,7 @@ import (
 	"github.com/DataDog/dd-trace-go/v2/ddtrace/internal/tracerstats"
 	sharedinternal "github.com/DataDog/dd-trace-go/v2/internal"
 	"github.com/DataDog/dd-trace-go/v2/internal/log"
+	"github.com/DataDog/dd-trace-go/v2/internal/processtags"
 	"github.com/DataDog/dd-trace-go/v2/internal/samplernames"
 	"github.com/DataDog/dd-trace-go/v2/internal/telemetry"
 )
@@ -488,6 +489,9 @@ func (t *trace) setTraceTags(s *Span) {
 	if s.context != nil && s.context.traceID.HasUpper() {
 		s.setMeta(keyTraceID128, s.context.traceID.UpperHex())
 	}
+	if pTags := processtags.Get().String(); pTags != "" {
+		s.setMeta(keyProcessTags, pTags)
+	}
 }
 
 // finishedOne acknowledges that another span in the trace has finished, and checks

ddtrace/tracer/spancontext_test.go

@@ -10,13 +10,15 @@ import (
 	"errors"
 	"fmt"
 	"math"
+	"strconv"
 	"sync"
 	"testing"
 	"time"
 
 	"github.com/DataDog/dd-trace-go/v2/ddtrace/ext"
 	"github.com/DataDog/dd-trace-go/v2/internal/globalconfig"
 	"github.com/DataDog/dd-trace-go/v2/internal/log"
+	"github.com/DataDog/dd-trace-go/v2/internal/processtags"
 	"github.com/DataDog/dd-trace-go/v2/internal/samplernames"
 	"github.com/DataDog/dd-trace-go/v2/internal/telemetry"
 	"github.com/DataDog/dd-trace-go/v2/internal/telemetry/telemetrytest"
@@ -1025,6 +1027,59 @@ func TestSpanIDHexEncoded(t *testing.T) {
 	assert.Equal(t, spanIDHexEncoded(math.MaxUint64, 16), sid)
 }
 
+func TestSpanProcessTags(t *testing.T) {
+	testCases := []struct {
+		name    string
+		enabled bool
+	}{
+		{
+			name:    "disabled",
+			enabled: false,
+		},
+		{
+			name:    "enabled",
+			enabled: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Setenv("DD_EXPERIMENTAL_COLLECT_PROCESS_TAGS_ENABLED", strconv.FormatBool(tc.enabled))
+			processtags.ResetConfig()
+			tracer, transport, flush, stop, err := startTestTracer(t)
+			assert.NoError(t, err)
+			t.Cleanup(stop)
+
+			p := tracer.StartSpan("p")
+			c1 := p.StartChild("c1")
+			c2 := p.StartChild("c2")
+			c11 := c1.StartChild("c1-1")
+
+			c11.Finish()
+			c2.Finish()
+			c1.Finish()
+			p.Finish()
+
+			flush(1)
+			traces := transport.Traces()
+			require.Len(t, traces, 1)
+			require.Len(t, traces[0], 4)
+
+			root := traces[0][0]
+			assert.Equal(t, "p", root.name)
+			if tc.enabled {
+				assert.NotEmpty(t, root.meta["_dd.tags.process"])
+			} else {
+				assert.NotContains(t, root.meta, "_dd.tags.process")
+			}
+
+			for _, s := range traces[0][1:] {
+				assert.NotContains(t, s.meta, "_dd.tags.process")
+			}
+		})
+	}
+}
+
 func BenchmarkSpanIDHexEncoded(b *testing.B) {
 	for n := 0; n < b.N; n++ {
 		_ = spanIDHexEncoded(32, 16)

internal/processtags/processtags.go

@@ -0,0 +1,138 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2025 Datadog, Inc.
+
+package processtags
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+
+	"github.com/DataDog/datadog-agent/pkg/trace/traceutil"
+
+	"github.com/DataDog/dd-trace-go/v2/internal"
+	"github.com/DataDog/dd-trace-go/v2/internal/log"
+)
+
+const (
+	tagEntrypointName    = "entrypoint.name"
+	tagEntrypointBasedir = "entrypoint.basedir"
+	tagEntrypointWorkdir = "entrypoint.workdir"
+)
+
+var (
+	enabled bool
+	pTags   *ProcessTags
+)
+
+func init() {
+	ResetConfig()
+}
+
+type ProcessTags struct {
+	mu    sync.RWMutex
+	tags  map[string]string
+	str   string
+	slice []string
+}
+
+// String returns the string representation of the process tags.
+func (p *ProcessTags) String() string {
+	if p == nil {
+		return ""
+	}
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return p.str
+}
+
+// Slice returns the string slice representation of the process tags.
+func (p *ProcessTags) Slice() []string {
+	if p == nil {
+		return nil
+	}
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return p.slice
+}
+
+func (p *ProcessTags) mergeTags(newTags map[string]string) {
+	if len(newTags) == 0 {
+		return
+	}
+	pTags.mu.Lock()
+	defer pTags.mu.Unlock()
+
+	if p.tags == nil {
+		p.tags = make(map[string]string)
+	}
+	for k, v := range newTags {
+		p.tags[k] = v
+	}
+
+	tagsSlice := make([]string, 0, len(p.tags))
+	var b strings.Builder
+	first := true
+	for k, val := range p.tags {
+		if !first {
+			b.WriteByte(',')
+		}
+		first = false
+		keyVal := traceutil.NormalizeTag(k + ":" + val)
+		b.WriteString(keyVal)
+		tagsSlice = append(tagsSlice, keyVal)
+	}
+	p.slice = tagsSlice
+	p.str = b.String()
+}
+
+// ResetConfig initializes the configuration and process tags collection. This is useful for tests.
+func ResetConfig() {
+	enabled = internal.BoolEnv("DD_EXPERIMENTAL_COLLECT_PROCESS_TAGS_ENABLED", false)
+	if !enabled {
+		return
+	}
+	pTags = &ProcessTags{}
+	tags := collectInitialProcessTags()
+	if len(tags) > 0 {
+		AddTags(tags)
+	}
+}
+
+func collectInitialProcessTags() map[string]string {
+	tags := make(map[string]string)
+	execPath, err := os.Executable()
+	if err != nil {
+		log.Debug("failed to get binary path: %v", err)
+	} else {
+		baseDirName := filepath.Base(filepath.Dir(execPath))
+		tags[tagEntrypointName] = filepath.Base(execPath)
+		tags[tagEntrypointBasedir] = baseDirName
+	}
+	wd, err := os.Getwd()
+	if err != nil {
+		log.Debug("failed to get working directory: %v", err)
+	} else {
+		tags[tagEntrypointWorkdir] = filepath.Base(wd)
+	}
+	return tags
+}
+
+// Get returns the global process tags.
+func Get() *ProcessTags {
+	if !enabled {
+		return nil
+	}
+	return pTags
+}
+
+// AddTags merges the given tags into the global processTags map.
+func AddTags(tags map[string]string) {
+	if !enabled {
+		return
+	}
+	pTags.mergeTags(tags)
+}

internal/processtags/processtags_test.go

@@ -0,0 +1,33 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2025 Datadog, Inc.
+
+package processtags
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestProcessTags(t *testing.T) {
+	t.Run("enabled", func(t *testing.T) {
+		t.Setenv("DD_EXPERIMENTAL_COLLECT_PROCESS_TAGS_ENABLED", "true")
+		ResetConfig()
+
+		p := Get()
+		assert.NotNil(t, p)
+		assert.NotEmpty(t, p.String())
+		assert.NotEmpty(t, p.Slice())
+	})
+
+	t.Run("disabled", func(t *testing.T) {
+		t.Setenv("DD_EXPERIMENTAL_COLLECT_PROCESS_TAGS_ENABLED", "false")
+		ResetConfig()
+
+		p := Get()
+		assert.Nil(t, p)
+		assert.Empty(t, p.String())
+		assert.Empty(t, p.Slice())
+	})
+}