snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

stats/opentelemetry/opentelemetry.go

@@ -0,0 +1,626 @@
+/*
+ * Copyright 2024 gRPC 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 opentelemetry implements opentelemetry instrumentation code for
+// gRPC-Go clients and servers.
+//
+// For details on configuring opentelemetry and various instruments that this
+// package creates, see
+// [gRPC OpenTelemetry Metrics](https://grpc.io/docs/guides/opentelemetry-metrics/).
+package opentelemetry
+
+import (
+	"context"
+	"strings"
+	"sync/atomic"
+	"time"
+
+	otelattribute "go.opentelemetry.io/otel/attribute"
+	otelmetric "go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/metric/noop"
+	"go.opentelemetry.io/otel/trace"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	experimental "google.golang.org/grpc/experimental/opentelemetry"
+	estats "google.golang.org/grpc/experimental/stats"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal"
+	"google.golang.org/grpc/stats"
+	otelinternal "google.golang.org/grpc/stats/opentelemetry/internal"
+)
+
+func init() {
+	otelinternal.SetPluginOption = func(o *Options, po otelinternal.PluginOption) {
+		o.MetricsOptions.pluginOption = po
+		// Log an error if one of the options is missing.
+		if (o.TraceOptions.TextMapPropagator == nil) != (o.TraceOptions.TracerProvider == nil) {
+			logger.Warning("Tracing will not be recorded because traceOptions are not set properly: one of TextMapPropagator or TracerProvider is missing")
+		}
+	}
+}
+
+var (
+	logger          = grpclog.Component("otel-plugin")
+	canonicalString = internal.CanonicalString.(func(codes.Code) string)
+	joinDialOptions = internal.JoinDialOptions.(func(...grpc.DialOption) grpc.DialOption)
+)
+
+// Options are the options for OpenTelemetry instrumentation.
+type Options struct {
+	// MetricsOptions are the metrics options for OpenTelemetry instrumentation.
+	MetricsOptions MetricsOptions
+	// TraceOptions are the tracing options for OpenTelemetry instrumentation.
+	TraceOptions experimental.TraceOptions
+}
+
+func (o *Options) isMetricsEnabled() bool {
+	return o.MetricsOptions.MeterProvider != nil
+}
+
+func (o *Options) isTracingEnabled() bool {
+	return o.TraceOptions.TracerProvider != nil
+}
+
+// MetricsOptions are the metrics options for OpenTelemetry instrumentation.
+type MetricsOptions struct {
+	// MeterProvider is the MeterProvider instance that will be used to create
+	// instruments. To enable metrics collection, set a meter provider. If
+	// unset, no metrics will be recorded.
+	MeterProvider otelmetric.MeterProvider
+
+	// Metrics are the metrics to instrument. Will create instrument and record telemetry
+	// for corresponding metric supported by the client and server
+	// instrumentation components if applicable. If not set, the default metrics
+	// will be recorded.
+	Metrics *stats.MetricSet
+
+	// MethodAttributeFilter is a function that determines whether to record the
+	// method name of RPCs as an attribute, or to bucket into "other". Take care
+	// to limit the values allowed, as allowing too many will increase
+	// cardinality and could cause severe memory or performance problems.
+	//
+	// This only applies for server-side metrics.  For clients, to record the
+	// method name in the attributes, pass grpc.StaticMethodCallOption to Invoke
+	// or NewStream. Note that when using protobuf generated clients, this
+	// CallOption is included automatically.
+	MethodAttributeFilter func(string) bool
+
+	// OptionalLabels specifies a list of optional labels to enable on any
+	// metrics that support them.
+	OptionalLabels []string
+
+	// pluginOption is used to get labels to attach to certain metrics, if set.
+	pluginOption otelinternal.PluginOption
+}
+
+// DialOption returns a dial option which enables OpenTelemetry instrumentation
+// code for a grpc.ClientConn.
+//
+// Client applications interested in instrumenting their grpc.ClientConn should
+// pass the dial option returned from this function as a dial option to
+// grpc.NewClient().
+//
+// For the metrics supported by this instrumentation code, specify the client
+// metrics to record in metrics options. Also provide an implementation of a
+// MeterProvider. If the passed in Meter Provider does not have the view
+// configured for an individual metric turned on, the API call in this component
+// will create a default view for that metric.
+//
+// For the traces supported by this instrumentation code, provide an
+// implementation of a TextMapPropagator and OpenTelemetry TracerProvider.
+func DialOption(o Options) grpc.DialOption {
+	var metricsOpts, tracingOpts []grpc.DialOption
+
+	if o.isMetricsEnabled() {
+		metricsHandler := &clientMetricsHandler{options: o}
+		metricsHandler.initializeMetrics()
+		metricsOpts = append(metricsOpts, grpc.WithChainUnaryInterceptor(metricsHandler.unaryInterceptor), grpc.WithChainStreamInterceptor(metricsHandler.streamInterceptor), grpc.WithStatsHandler(metricsHandler))
+	}
+	if o.isTracingEnabled() {
+		tracingHandler := &clientTracingHandler{options: o}
+		tracingHandler.initializeTraces()
+		tracingOpts = append(tracingOpts, grpc.WithChainUnaryInterceptor(tracingHandler.unaryInterceptor), grpc.WithChainStreamInterceptor(tracingHandler.streamInterceptor), grpc.WithStatsHandler(tracingHandler))
+	}
+	return joinDialOptions(append(metricsOpts, tracingOpts...)...)
+}
+
+var joinServerOptions = internal.JoinServerOptions.(func(...grpc.ServerOption) grpc.ServerOption)
+
+// ServerOption returns a server option which enables OpenTelemetry
+// instrumentation code for a grpc.Server.
+//
+// Server applications interested in instrumenting their grpc.Server should pass
+// the server option returned from this function as an argument to
+// grpc.NewServer().
+//
+// For the metrics supported by this instrumentation code, specify the server
+// metrics to record in metrics options. Also provide an implementation of a
+// MeterProvider. If the passed in Meter Provider does not have the view
+// configured for an individual metric turned on, the API call in this component
+// will create a default view for that metric.
+//
+// For the traces supported by this instrumentation code, provide an
+// implementation of a TextMapPropagator and OpenTelemetry TracerProvider.
+func ServerOption(o Options) grpc.ServerOption {
+	var metricsOpts, tracingOpts []grpc.ServerOption
+
+	if o.isMetricsEnabled() {
+		metricsHandler := &serverMetricsHandler{options: o}
+		metricsHandler.initializeMetrics()
+		metricsOpts = append(metricsOpts, grpc.ChainUnaryInterceptor(metricsHandler.unaryInterceptor), grpc.ChainStreamInterceptor(metricsHandler.streamInterceptor), grpc.StatsHandler(metricsHandler))
+	}
+	if o.isTracingEnabled() {
+		tracingHandler := &serverTracingHandler{options: o}
+		tracingHandler.initializeTraces()
+		tracingOpts = append(tracingOpts, grpc.StatsHandler(tracingHandler))
+	}
+	return joinServerOptions(append(metricsOpts, tracingOpts...)...)
+}
+
+// callInfo is information pertaining to the lifespan of the RPC client side.
+type callInfo struct {
+	target string
+
+	method string
+
+	// nameResolutionEventAdded is set when the resolver delay trace event
+	// is added. Prevents duplicate events, since it is reported per-attempt.
+	nameResolutionEventAdded atomic.Bool
+	// previousRPCAttempts holds the count of RPC attempts that have happened
+	// before current attempt. Transparent retries are excluded.
+	previousRPCAttempts atomic.Uint32
+}
+
+type callInfoKey struct{}
+
+// getCallInfo returns the callInfo stored in the context, or nil
+// if there isn't one.
+func getCallInfo(ctx context.Context) *callInfo {
+	ci, _ := ctx.Value(callInfoKey{}).(*callInfo)
+	return ci
+}
+
+// rpcInfo is RPC information scoped to the RPC attempt life span client side,
+// and the RPC life span server side.
+type rpcInfo struct {
+	ai *attemptInfo
+}
+
+type clientRPCInfoKey struct{}
+type serverRPCInfoKey struct{}
+
+// clientRPCInfo returns the rpcInfo stored in the context for client, or nil
+// if there isn't one.
+func clientRPCInfo(ctx context.Context) *rpcInfo {
+	ri, _ := ctx.Value(clientRPCInfoKey{}).(*rpcInfo)
+	return ri
+}
+
+// serverRPCInfo returns the rpcInfo stored in the context for server, or nil
+// if there isn't one.
+func serverRPCInfo(ctx context.Context) *rpcInfo {
+	ri, _ := ctx.Value(serverRPCInfoKey{}).(*rpcInfo)
+	return ri
+}
+
+func getOrCreateClientRPCInfo(ctx context.Context, info *stats.RPCTagInfo) (context.Context, *rpcInfo) {
+	ri := clientRPCInfo(ctx)
+	if ri != nil {
+		return ctx, ri
+	}
+	ri = &rpcInfo{
+		ai: &attemptInfo{
+			startTime: time.Now(),
+			method:    removeLeadingSlash(info.FullMethodName),
+			xdsLabels: map[string]string{
+				// The defaults for all the per call labels from a plugin that
+				// executes on the callpath that this OpenTelemetry component
+				// currently supports.
+				"grpc.lb.locality":        "",
+				"grpc.lb.backend_service": "",
+			},
+		},
+	}
+	return context.WithValue(ctx, clientRPCInfoKey{}, ri), ri
+}
+
+func getOrCreateServerRPCInfo(ctx context.Context, info *stats.RPCTagInfo, options MetricsOptions) (context.Context, *rpcInfo) {
+	ri := serverRPCInfo(ctx)
+	if ri != nil {
+		return ctx, ri
+	}
+	method := info.FullMethodName
+	if options.MethodAttributeFilter != nil {
+		if !options.MethodAttributeFilter(method) {
+			method = "other"
+		}
+	}
+	server := internal.ServerFromContext.(func(context.Context) *grpc.Server)(ctx)
+	if server == nil { // Shouldn't happen, defensive programming.
+		logger.Error("ctx passed into server side stats handler has no grpc server ref")
+		method = "other"
+	} else {
+		isRegisteredMethod := internal.IsRegisteredMethod.(func(*grpc.Server, string) bool)
+		if !isRegisteredMethod(server, method) {
+			method = "other"
+		}
+	}
+
+	ri = &rpcInfo{
+		ai: &attemptInfo{
+			startTime: time.Now(),
+			method:    removeLeadingSlash(method),
+		},
+	}
+	return context.WithValue(ctx, serverRPCInfoKey{}, ri), ri
+}
+
+func removeLeadingSlash(mn string) string {
+	return strings.TrimLeft(mn, "/")
+}
+
+// attemptInfo is RPC information scoped to the RPC attempt life span client
+// side, and the RPC life span server side.
+type attemptInfo struct {
+	// access these counts atomically for hedging in the future:
+	// number of bytes after compression (within each message) from side (client
+	// || server).
+	sentCompressedBytes int64
+	// number of compressed bytes received (within each message) received on
+	// side (client || server).
+	recvCompressedBytes int64
+
+	startTime time.Time
+	method    string
+
+	pluginOptionLabels map[string]string // pluginOptionLabels to attach to metrics emitted
+	xdsLabels          map[string]string
+
+	// traceSpan is data used for recording traces.
+	traceSpan trace.Span
+	// message counters for sent and received messages (used for
+	// generating message IDs), and the number of previous RPC attempts for the
+	// associated call.
+	countSentMsg uint32
+	countRecvMsg uint32
+}
+
+type clientMetrics struct {
+	// "grpc.client.attempt.started"
+	attemptStarted otelmetric.Int64Counter
+	// "grpc.client.attempt.duration"
+	attemptDuration otelmetric.Float64Histogram
+	// "grpc.client.attempt.sent_total_compressed_message_size"
+	attemptSentTotalCompressedMessageSize otelmetric.Int64Histogram
+	// "grpc.client.attempt.rcvd_total_compressed_message_size"
+	attemptRcvdTotalCompressedMessageSize otelmetric.Int64Histogram
+	// "grpc.client.call.duration"
+	callDuration otelmetric.Float64Histogram
+}
+
+type serverMetrics struct {
+	// "grpc.server.call.started"
+	callStarted otelmetric.Int64Counter
+	// "grpc.server.call.sent_total_compressed_message_size"
+	callSentTotalCompressedMessageSize otelmetric.Int64Histogram
+	// "grpc.server.call.rcvd_total_compressed_message_size"
+	callRcvdTotalCompressedMessageSize otelmetric.Int64Histogram
+	// "grpc.server.call.duration"
+	callDuration otelmetric.Float64Histogram
+}
+
+func createInt64Counter(setOfMetrics map[string]bool, metricName string, meter otelmetric.Meter, options ...otelmetric.Int64CounterOption) otelmetric.Int64Counter {
+	if _, ok := setOfMetrics[metricName]; !ok {
+		return noop.Int64Counter{}
+	}
+	ret, err := meter.Int64Counter(string(metricName), options...)
+	if err != nil {
+		logger.Errorf("failed to register metric \"%v\", will not record: %v", metricName, err)
+		return noop.Int64Counter{}
+	}
+	return ret
+}
+
+func createInt64UpDownCounter(setOfMetrics map[string]bool, metricName string, meter otelmetric.Meter, options ...otelmetric.Int64UpDownCounterOption) otelmetric.Int64UpDownCounter {
+	if _, ok := setOfMetrics[metricName]; !ok {
+		return noop.Int64UpDownCounter{}
+	}
+	ret, err := meter.Int64UpDownCounter(string(metricName), options...)
+	if err != nil {
+		logger.Errorf("Failed to register metric \"%v\", will not record: %v", metricName, err)
+		return noop.Int64UpDownCounter{}
+	}
+	return ret
+}
+
+func createFloat64Counter(setOfMetrics map[string]bool, metricName string, meter otelmetric.Meter, options ...otelmetric.Float64CounterOption) otelmetric.Float64Counter {
+	if _, ok := setOfMetrics[metricName]; !ok {
+		return noop.Float64Counter{}
+	}
+	ret, err := meter.Float64Counter(string(metricName), options...)
+	if err != nil {
+		logger.Errorf("failed to register metric \"%v\", will not record: %v", metricName, err)
+		return noop.Float64Counter{}
+	}
+	return ret
+}
+
+func createInt64Histogram(setOfMetrics map[string]bool, metricName string, meter otelmetric.Meter, options ...otelmetric.Int64HistogramOption) otelmetric.Int64Histogram {
+	if _, ok := setOfMetrics[metricName]; !ok {
+		return noop.Int64Histogram{}
+	}
+	ret, err := meter.Int64Histogram(string(metricName), options...)
+	if err != nil {
+		logger.Errorf("failed to register metric \"%v\", will not record: %v", metricName, err)
+		return noop.Int64Histogram{}
+	}
+	return ret
+}
+
+func createFloat64Histogram(setOfMetrics map[string]bool, metricName string, meter otelmetric.Meter, options ...otelmetric.Float64HistogramOption) otelmetric.Float64Histogram {
+	if _, ok := setOfMetrics[metricName]; !ok {
+		return noop.Float64Histogram{}
+	}
+	ret, err := meter.Float64Histogram(string(metricName), options...)
+	if err != nil {
+		logger.Errorf("failed to register metric \"%v\", will not record: %v", metricName, err)
+		return noop.Float64Histogram{}
+	}
+	return ret
+}
+
+func createInt64Gauge(setOfMetrics map[string]bool, metricName string, meter otelmetric.Meter, options ...otelmetric.Int64GaugeOption) otelmetric.Int64Gauge {
+	if _, ok := setOfMetrics[metricName]; !ok {
+		return noop.Int64Gauge{}
+	}
+	ret, err := meter.Int64Gauge(string(metricName), options...)
+	if err != nil {
+		logger.Errorf("failed to register metric \"%v\", will not record: %v", metricName, err)
+		return noop.Int64Gauge{}
+	}
+	return ret
+}
+
+// createInt64ObservableGauge initializes an OTel Int64ObservableGauge if the metric is enabled.
+func createInt64ObservableGauge(setOfMetrics map[string]bool, metricName string, meter otelmetric.Meter, options ...otelmetric.Int64ObservableGaugeOption) otelmetric.Int64ObservableGauge {
+	if _, ok := setOfMetrics[metricName]; !ok {
+		n, _ := noop.NewMeterProvider().Meter("noop").Int64ObservableGauge("noop")
+		return n
+	}
+	ret, err := meter.Int64ObservableGauge(metricName, options...)
+	if err != nil {
+		logger.Errorf("failed to register metric %q, will not record: %v", metricName, err)
+		n, _ := noop.NewMeterProvider().Meter("noop").Int64ObservableGauge("noop")
+		return n
+	}
+	return ret
+}
+
+func optionFromLabels(labelKeys []string, optionalLabelKeys []string, optionalLabels []string, labelVals ...string) otelmetric.MeasurementOption {
+	var attributes []otelattribute.KeyValue
+
+	// Once it hits here lower level has guaranteed length of labelVals matches
+	// labelKeys + optionalLabelKeys.
+	for i, label := range labelKeys {
+		attributes = append(attributes, otelattribute.String(label, labelVals[i]))
+	}
+
+	for i, label := range optionalLabelKeys {
+		for _, optLabel := range optionalLabels { // o(n) could build out a set but n is currently capped at < 5
+			if label == optLabel {
+				attributes = append(attributes, otelattribute.String(label, labelVals[i+len(labelKeys)]))
+			}
+		}
+	}
+	return otelmetric.WithAttributeSet(otelattribute.NewSet(attributes...))
+}
+
+// registryMetrics implements MetricsRecorder for the client and server stats
+// handlers.
+type registryMetrics struct {
+	internal.EnforceMetricsRecorderEmbedding
+	intCounts       map[*estats.MetricDescriptor]otelmetric.Int64Counter
+	floatCounts     map[*estats.MetricDescriptor]otelmetric.Float64Counter
+	intHistos       map[*estats.MetricDescriptor]otelmetric.Int64Histogram
+	floatHistos     map[*estats.MetricDescriptor]otelmetric.Float64Histogram
+	intGauges       map[*estats.MetricDescriptor]otelmetric.Int64Gauge
+	intUpDownCounts map[*estats.MetricDescriptor]otelmetric.Int64UpDownCounter
+
+	// Asynchronous (Observable) Instruments
+	intObservableGauges map[*estats.MetricDescriptor]otelmetric.Int64ObservableGauge
+
+	meter          otelmetric.Meter
+	optionalLabels []string
+}
+
+func (rm *registryMetrics) registerMetrics(metrics *stats.MetricSet, meter otelmetric.Meter) {
+	rm.meter = meter
+	rm.intCounts = make(map[*estats.MetricDescriptor]otelmetric.Int64Counter)
+	rm.floatCounts = make(map[*estats.MetricDescriptor]otelmetric.Float64Counter)
+	rm.intHistos = make(map[*estats.MetricDescriptor]otelmetric.Int64Histogram)
+	rm.floatHistos = make(map[*estats.MetricDescriptor]otelmetric.Float64Histogram)
+	rm.intGauges = make(map[*estats.MetricDescriptor]otelmetric.Int64Gauge)
+	rm.intUpDownCounts = make(map[*estats.MetricDescriptor]otelmetric.Int64UpDownCounter)
+	rm.intObservableGauges = make(map[*estats.MetricDescriptor]otelmetric.Int64ObservableGauge)
+
+	for metric := range metrics.Metrics() {
+		desc := estats.DescriptorForMetric(metric)
+		if desc == nil {
+			// Either the metric was per call or the metric is not registered.
+			// Thus, if this component ever receives the desc as a handle in
+			// record it will be a no-op.
+			continue
+		}
+		switch desc.Type {
+		case estats.MetricTypeIntCount:
+			rm.intCounts[desc] = createInt64Counter(metrics.Metrics(), desc.Name, meter, otelmetric.WithUnit(desc.Unit), otelmetric.WithDescription(desc.Description))
+		case estats.MetricTypeFloatCount:
+			rm.floatCounts[desc] = createFloat64Counter(metrics.Metrics(), desc.Name, meter, otelmetric.WithUnit(desc.Unit), otelmetric.WithDescription(desc.Description))
+		case estats.MetricTypeIntHisto:
+			rm.intHistos[desc] = createInt64Histogram(metrics.Metrics(), desc.Name, meter, otelmetric.WithUnit(desc.Unit), otelmetric.WithDescription(desc.Description), otelmetric.WithExplicitBucketBoundaries(desc.Bounds...))
+		case estats.MetricTypeFloatHisto:
+			rm.floatHistos[desc] = createFloat64Histogram(metrics.Metrics(), desc.Name, meter, otelmetric.WithUnit(desc.Unit), otelmetric.WithDescription(desc.Description), otelmetric.WithExplicitBucketBoundaries(desc.Bounds...))
+		case estats.MetricTypeIntGauge:
+			rm.intGauges[desc] = createInt64Gauge(metrics.Metrics(), desc.Name, meter, otelmetric.WithUnit(desc.Unit), otelmetric.WithDescription(desc.Description))
+		case estats.MetricTypeIntUpDownCount:
+			rm.intUpDownCounts[desc] = createInt64UpDownCounter(metrics.Metrics(), desc.Name, meter, otelmetric.WithUnit(desc.Unit), otelmetric.WithDescription(desc.Description))
+		case estats.MetricTypeIntAsyncGauge:
+			rm.intObservableGauges[desc] = createInt64ObservableGauge(metrics.Metrics(), desc.Name, meter, otelmetric.WithUnit(desc.Unit), otelmetric.WithDescription(desc.Description))
+		}
+	}
+}
+
+func (rm *registryMetrics) RecordInt64Count(handle *estats.Int64CountHandle, incr int64, labels ...string) {
+	desc := handle.Descriptor()
+	if ic, ok := rm.intCounts[desc]; ok {
+		ao := optionFromLabels(desc.Labels, desc.OptionalLabels, rm.optionalLabels, labels...)
+		ic.Add(context.TODO(), incr, ao)
+	}
+}
+
+func (rm *registryMetrics) RecordInt64UpDownCount(handle *estats.Int64UpDownCountHandle, incr int64, labels ...string) {
+	desc := handle.Descriptor()
+	if ic, ok := rm.intUpDownCounts[desc]; ok {
+		ao := optionFromLabels(desc.Labels, desc.OptionalLabels, rm.optionalLabels, labels...)
+		ic.Add(context.TODO(), incr, ao)
+	}
+}
+
+func (rm *registryMetrics) RecordFloat64Count(handle *estats.Float64CountHandle, incr float64, labels ...string) {
+	desc := handle.Descriptor()
+	if fc, ok := rm.floatCounts[desc]; ok {
+		ao := optionFromLabels(desc.Labels, desc.OptionalLabels, rm.optionalLabels, labels...)
+		fc.Add(context.TODO(), incr, ao)
+	}
+}
+
+func (rm *registryMetrics) RecordInt64Histo(handle *estats.Int64HistoHandle, incr int64, labels ...string) {
+	desc := handle.Descriptor()
+	if ih, ok := rm.intHistos[desc]; ok {
+		ao := optionFromLabels(desc.Labels, desc.OptionalLabels, rm.optionalLabels, labels...)
+		ih.Record(context.TODO(), incr, ao)
+	}
+}
+
+func (rm *registryMetrics) RecordFloat64Histo(handle *estats.Float64HistoHandle, incr float64, labels ...string) {
+	desc := handle.Descriptor()
+	if fh, ok := rm.floatHistos[desc]; ok {
+		ao := optionFromLabels(desc.Labels, desc.OptionalLabels, rm.optionalLabels, labels...)
+		fh.Record(context.TODO(), incr, ao)
+	}
+}
+
+func (rm *registryMetrics) RecordInt64Gauge(handle *estats.Int64GaugeHandle, incr int64, labels ...string) {
+	desc := handle.Descriptor()
+	if ig, ok := rm.intGauges[desc]; ok {
+		ao := optionFromLabels(desc.Labels, desc.OptionalLabels, rm.optionalLabels, labels...)
+		ig.Record(context.TODO(), incr, ao)
+	}
+}
+
+// RegisterAsyncReporter will register a callback with the underlying OpenTelemetry
+// Meter for the provided descriptors.
+//
+// It will map the provided descriptors to their corresponding OTel Observable
+// instruments. If no instruments match the descriptors, registration is
+// skipped.
+//
+// The returned cleanup function unregisters the callback from the Meter.
+// RegisterAsyncReporter registers a callback with the OpenTelemetry Meter.
+func (rm *registryMetrics) RegisterAsyncReporter(reporter estats.AsyncMetricReporter, metrics ...estats.AsyncMetric) func() {
+	observables := make([]otelmetric.Observable, 0, len(metrics))
+	observableMap := make(map[*estats.MetricDescriptor]otelmetric.Observable, len(metrics))
+
+	for _, m := range metrics {
+		d := m.Descriptor()
+		if inst, ok := rm.intObservableGauges[d]; ok {
+			observables = append(observables, inst)
+			observableMap[d] = inst
+		}
+	}
+
+	if len(observables) == 0 {
+		return func() {}
+	}
+
+	cbWrapper := func(_ context.Context, o otelmetric.Observer) error {
+		adapter := &observerAdapter{
+			observableMap:  observableMap,
+			optionalLabels: rm.optionalLabels,
+			delegate:       o,
+		}
+		reporter.Report(adapter)
+		return nil
+	}
+
+	reg, err := rm.meter.RegisterCallback(cbWrapper, observables...)
+	if err != nil {
+		logger.Warningf("grpc: failed to register callback for async metrics: %v", err)
+		return func() {}
+	}
+
+	return func() {
+		err = reg.Unregister()
+		if err != nil {
+			logger.Errorf("grpc: failed to unregister callback for async metrics: %v", err)
+		}
+	}
+}
+
+// Users of this component should use these bucket boundaries as part of their
+// SDK MeterProvider passed in. This component sends this as "advice" to the
+// API, which works, however this stability is not guaranteed, so for safety the
+// SDK Meter Provider provided should set these bounds for corresponding
+// metrics.
+var (
+	// DefaultLatencyBounds are the default bounds for latency metrics.
+	DefaultLatencyBounds = []float64{0, 0.00001, 0.00005, 0.0001, 0.0003, 0.0006, 0.0008, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.008, 0.01, 0.013, 0.016, 0.02, 0.025, 0.03, 0.04, 0.05, 0.065, 0.08, 0.1, 0.13, 0.16, 0.2, 0.25, 0.3, 0.4, 0.5, 0.65, 0.8, 1, 2, 5, 10, 20, 50, 100} // provide "advice" through API, SDK should set this too
+	// DefaultSizeBounds are the default bounds for metrics which record size.
+	DefaultSizeBounds = []float64{0, 1024, 2048, 4096, 16384, 65536, 262144, 1048576, 4194304, 16777216, 67108864, 268435456, 1073741824, 4294967296}
+	// defaultPerCallMetrics are the default metrics provided by this module.
+	defaultPerCallMetrics = stats.NewMetricSet(ClientAttemptStartedMetricName, ClientAttemptDurationMetricName, ClientAttemptSentCompressedTotalMessageSizeMetricName, ClientAttemptRcvdCompressedTotalMessageSizeMetricName, ClientCallDurationMetricName, ServerCallStartedMetricName, ServerCallSentCompressedTotalMessageSizeMetricName, ServerCallRcvdCompressedTotalMessageSizeMetricName, ServerCallDurationMetricName)
+)
+
+// DefaultMetrics returns a set of default OpenTelemetry metrics.
+//
+// This should only be invoked after init time.
+func DefaultMetrics() *stats.MetricSet {
+	return defaultPerCallMetrics.Join(estats.DefaultMetrics)
+}
+
+type observerAdapter struct {
+	observableMap  map[*estats.MetricDescriptor]otelmetric.Observable
+	optionalLabels []string
+	delegate       otelmetric.Observer
+}
+
+// RecordInt64AsyncGauge records the measurement alongside labels on the int
+// gauge associated with the provided handle.
+func (a *observerAdapter) RecordInt64AsyncGauge(handle *estats.Int64AsyncGaugeHandle, val int64, labels ...string) {
+	desc := handle.Descriptor()
+	observable, ok := a.observableMap[desc]
+	if !ok {
+		return
+	}
+
+	ao := optionFromLabels(desc.Labels, desc.OptionalLabels, a.optionalLabels, labels...)
+
+	switch obs := observable.(type) {
+	case otelmetric.Int64ObservableGauge:
+		a.delegate.ObserveInt64(obs, val, ao)
+	default:
+	}
+}