Support multiple entity refs in the Resource

attribute/set.go

@@ -307,6 +307,15 @@ func filteredToFront(slice []KeyValue, keep Filter) int {
 	return j
 }
 
+func (l *Set) Clone() Set {
+	s, _ := l.Filter(
+		func(KeyValue) bool {
+			return true
+		},
+	)
+	return s
+}
+
 // Filter returns a filtered copy of this Set. See the documentation for
 // NewSetWithSortableFiltered for more details.
 func (l *Set) Filter(re Filter) (Set, []KeyValue) {

example/dice/otel.go

@@ -20,6 +20,7 @@ import (
 	"time"
 
 	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
 	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
 	"go.opentelemetry.io/otel/propagation"
@@ -86,14 +87,28 @@ func setupOTelSDK(ctx context.Context, serviceName, serviceVersion string) (
 }
 
 func newResource(serviceName, serviceVersion string) (*resource.Resource, error) {
-	return resource.Merge(
-		resource.Default(),
-		resource.NewWithAttributes(
+	res, err := resource.New(
+		context.Background(),
+		resource.WithHost(),
+		resource.WithHostID(),
+		resource.WithProcess(),
+		resource.WithEntity(
 			semconv.SchemaURL,
-			semconv.ServiceName(serviceName),
-			semconv.ServiceVersion(serviceVersion),
+			"service",
+			[]attribute.KeyValue{
+				semconv.ServiceName(serviceName),
+				semconv.ServiceVersion(serviceVersion),
+			},
+			nil,
 		),
 	)
+	if err != nil {
+		return nil, err
+	}
+	return resource.Merge(
+		resource.Default(),
+		res,
+	)
 }
 
 func newPropagator() propagation.TextMapPropagator {

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

@@ -27,11 +27,21 @@ func Resource(r *resource.Resource) *resourcepb.Resource {
 	}
 
 	attrs := Iterator(r.Iter())
-	entityId := Iterator(r.EntityId().Iter())
 
-	return &resourcepb.Resource{
+	out := &resourcepb.Resource{
 		Attributes: attrs,
-		EntityType: r.EntityType(),
-		EntityId:   entityId,
 	}
+
+	for _, entity := range r.EntityRefs() {
+		out.Entities = append(
+			out.Entities, &resourcepb.ResourceEntityRef{
+				SchemaUrl:     entity.SchemaUrl(),
+				Type:          entity.Type(),
+				IdAttrKeys:    entity.Id(),
+				DescrAttrKeys: entity.Attrs(),
+			},
+		)
+	}
+
+	return out
 }

go.sum

@@ -9,6 +9,7 @@ github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=

sdk/resource/builtin.go

@@ -22,7 +22,6 @@ import (
 
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/sdk"
-	"go.opentelemetry.io/otel/sdk/resource/internal"
 	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
 )
 
@@ -42,10 +41,9 @@ type (
 	host struct{}
 
 	stringDetector struct {
-		schemaURL  string
-		K          attribute.Key
-		F          func() (string, error)
-		entityType string
+		schemaURL string
+		K         attribute.Key
+		F         func() (string, error)
 	}
 
 	defaultServiceNameDetector struct{}
@@ -70,7 +68,19 @@ func (telemetrySDK) Detect(context.Context) (*Resource, error) {
 
 // Detect returns a *Resource that describes the host being run on.
 func (host) Detect(ctx context.Context) (*Resource, error) {
-	return StringDetector(semconv.SchemaURL, semconv.HostNameKey, os.Hostname).Detect(ctx)
+	name, err := os.Hostname()
+	if err != nil {
+		return nil, err
+	}
+	return NewWithEntities(
+		[]Entity{
+			{
+				Type:      "host",
+				Attrs:     attribute.NewSet(semconv.HostName(name)),
+				SchemaURL: semconv.SchemaURL,
+			},
+		},
+	)
 }
 
 // StringDetector returns a Detector that will produce a *Resource
@@ -80,14 +90,6 @@ func StringDetector(schemaURL string, k attribute.Key, f func() (string, error))
 	return stringDetector{schemaURL: schemaURL, K: k, F: f}
 }
 
-// StringDetectorWithEntity returns a Detector that will produce a *Resource
-// containing the string as a value corresponding to k. The Id of entity of the
-// resource will also be set to the same key/value pair.
-// The resulting Resource will have the specified schemaURL.
-func StringDetectorWithEntity(schemaURL string, entityType string, k attribute.Key, f func() (string, error)) Detector {
-	return stringDetector{schemaURL: schemaURL, K: k, F: f, entityType: entityType}
-}
-
 // Detect returns a *Resource that describes the string as a value
 // corresponding to attribute.Key as well as the specific schemaURL.
 func (sd stringDetector) Detect(ctx context.Context) (*Resource, error) {
@@ -99,27 +101,26 @@ func (sd stringDetector) Detect(ctx context.Context) (*Resource, error) {
 	if !a.Valid() {
 		return nil, fmt.Errorf("invalid attribute: %q -> %q", a.Key, a.Value.Emit())
 	}
-	id := attribute.NewSet(sd.K.String(value))
-	entity := internal.EntityData{
-		Type:  sd.entityType,
-		Id:    id,
-		Attrs: id,
-	}
-	return NewWithEntity(sd.schemaURL, &entity), nil
+	return NewWithAttributes(sd.schemaURL, sd.K.String(value)), nil
 }
 
 // Detect implements Detector.
 func (defaultServiceNameDetector) Detect(ctx context.Context) (*Resource, error) {
-	return StringDetectorWithEntity(
-		semconv.SchemaURL,
-		"service",
-		semconv.ServiceNameKey,
-		func() (string, error) {
-			executable, err := os.Executable()
-			if err != nil {
-				return "unknown_service:go", nil
-			}
-			return "unknown_service:" + filepath.Base(executable), nil
+	serviceName := ""
+	executable, err := os.Executable()
+	if err != nil {
+		serviceName = "unknown_service:go"
+	} else {
+		serviceName = "unknown_service:" + filepath.Base(executable)
+	}
+
+	return NewWithEntities(
+		[]Entity{
+			{
+				Type:      "service",
+				Id:        attribute.NewSet(semconv.ServiceName(serviceName)),
+				SchemaURL: semconv.SchemaURL,
+			},
 		},
-	).Detect(ctx)
+	)
 }

sdk/resource/config.go

@@ -27,8 +27,8 @@ type config struct {
 	// SchemaURL to associate with the Resource.
 	schemaURL string
 
-	entityType string
-	entityId   []attribute.KeyValue
+	//entityType string
+	//entityId   []attribute.KeyValue
 }
 
 // Option is the interface that applies a configuration option.
@@ -96,20 +96,36 @@ func (o schemaURLOption) apply(cfg config) config {
 	return cfg
 }
 
-// WithEntity sets the schema URL for the configured resource.
-func WithEntity(entityType string, entityId ...attribute.KeyValue) Option {
-	return entityOption{entityType, entityId}
+type entityDetector struct {
+	SchemaURL string
+	Type      string
+	Id        []attribute.KeyValue
+	Attrs     []attribute.KeyValue
 }
 
-type entityOption struct {
-	entityType string
-	entityId   []attribute.KeyValue
+func (e entityDetector) Detect(ctx context.Context) (*Resource, error) {
+	return NewWithEntities(
+		[]Entity{
+			{
+				Type:      e.Type,
+				Id:        attribute.NewSet(e.Id...),
+				Attrs:     attribute.NewSet(e.Attrs...),
+				SchemaURL: e.SchemaURL,
+			},
+		},
+	)
 }
 
-func (o entityOption) apply(cfg config) config {
-	cfg.entityType = o.entityType
-	cfg.entityId = o.entityId
-	return cfg
+// WithEntity sets the schema URL for the configured resource.
+func WithEntity(schemaURL string, entityType string, id, attrs []attribute.KeyValue) Option {
+	return WithDetectors(
+		entityDetector{
+			SchemaURL: schemaURL,
+			Type:      entityType,
+			Id:        id,
+			Attrs:     attrs,
+		},
+	)
 }
 
 // WithOS adds all the OS attributes to the configured Resource.

sdk/resource/entity.go

@@ -0,0 +1,10 @@
+package resource
+
+import "go.opentelemetry.io/otel/attribute"
+
+type Entity struct {
+	Type      string
+	Id        attribute.Set
+	Attrs     attribute.Set
+	SchemaURL string
+}

sdk/resource/entityref.go

@@ -0,0 +1,49 @@
+package resource
+
+import "go.opentelemetry.io/otel/attribute"
+
+type resourceEntityRef struct {
+	schemaUrl string
+
+	// Defines the entity type, e.g "service", "k8s.pod", etc.
+	typ string
+
+	// Set of Resource attribute keys that identify the entity.
+	id map[attribute.Key]bool
+
+	// Set of Resource attribute keys that describe the entity.
+	attrs map[attribute.Key]bool
+
+	// id and attrs are cached as slices for faster exporting.
+	idAsSlice    []string
+	attrsAsSlice []string
+}
+
+// updateCache must be called after id or attrs are modified to make
+// sure the cache is up to date.
+func (r *resourceEntityRef) updateCache() {
+	r.idAsSlice = r.idAsSlice[:0]
+	for k := range r.id {
+		r.idAsSlice = append(r.idAsSlice, string(k))
+	}
+	r.attrsAsSlice = r.attrsAsSlice[:0]
+	for k := range r.attrs {
+		r.attrsAsSlice = append(r.attrsAsSlice, string(k))
+	}
+}
+
+func (r *resourceEntityRef) SchemaUrl() string {
+	return r.schemaUrl
+}
+
+func (r *resourceEntityRef) Type() string {
+	return r.typ
+}
+
+func (r *resourceEntityRef) Id() []string {
+	return r.idAsSlice
+}
+
+func (r *resourceEntityRef) Attrs() []string {
+	return r.attrsAsSlice
+}

sdk/resource/host_id.go

@@ -19,6 +19,7 @@ import (
 	"errors"
 	"strings"
 
+	"go.opentelemetry.io/otel/attribute"
 	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
 )
 
@@ -113,8 +114,13 @@ func (hostIDDetector) Detect(ctx context.Context) (*Resource, error) {
 		return nil, err
 	}
 
-	return NewWithAttributes(
-		semconv.SchemaURL,
-		semconv.HostID(hostID),
-	), nil
+	return NewWithEntities(
+		[]Entity{
+			{
+				Type:      "host",
+				Id:        attribute.NewSet(semconv.HostID(hostID)),
+				SchemaURL: semconv.SchemaURL,
+			},
+		},
+	)
 }