otel: conceal unwrapping for global async instrument registration

CHANGELOG.md

@@ -13,6 +13,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Add `go.opentelemetry.io/otel/sdk/metric/exemplar.AlwaysOffFilter`, which can be used to disable exemplar recording. (#5850)
 - Add `go.opentelemetry.io/otel/sdk/metric.WithExemplarFilter`, which can be used to configure the exemplar filter used by the metrics SDK. (#5850)
 
+### Fixed
+
+- Global MeterProvider registration correctly unwraps global instrument stubs. (#5881)
+
 <!-- Released section -->
 <!-- Don't change this section unless doing release -->
 

internal/global/alt_sdk_test.go

@@ -0,0 +1,175 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package global // import "go.opentelemetry.io/otel/internal/global"
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/metric/embedded"
+)
+
+type altMeterProvider struct {
+	t      *testing.T
+	meters []*altMeter
+	embedded.MeterProvider
+}
+
+var _ metric.MeterProvider = &altMeterProvider{}
+
+func (amp *altMeterProvider) Meter(name string, opts ...metric.MeterOption) metric.Meter {
+	am := &altMeter{
+		provider: amp,
+	}
+	amp.meters = append(amp.meters, am)
+	return am
+}
+
+type altMeter struct {
+	provider *altMeterProvider
+	cbs      []metric.Callback
+	embedded.Meter
+}
+
+var _ metric.Meter = &altMeter{}
+
+type testAsyncCounter struct {
+	meter *altMeter
+	embedded.Int64ObservableCounter
+	metric.Int64Observable
+}
+
+var _ metric.Int64ObservableCounter = &testAsyncCounter{}
+
+type altRegistration struct {
+	cb metric.Callback
+	embedded.Registration
+}
+
+type altObserver struct {
+	t *testing.T
+	embedded.Observer
+}
+
+func (*altRegistration) Unregister() error {
+	return nil
+}
+
+func (am *altMeter) Int64Counter(name string, options ...metric.Int64CounterOption) (metric.Int64Counter, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Int64UpDownCounter(name string, options ...metric.Int64UpDownCounterOption) (metric.Int64UpDownCounter, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Int64Histogram(name string, options ...metric.Int64HistogramOption) (metric.Int64Histogram, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Int64Gauge(name string, options ...metric.Int64GaugeOption) (metric.Int64Gauge, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Int64ObservableCounter(name string, options ...metric.Int64ObservableCounterOption) (metric.Int64ObservableCounter, error) {
+	return &testAsyncCounter{
+		meter: am,
+	}, nil
+}
+
+func (am *altMeter) Int64ObservableUpDownCounter(name string, options ...metric.Int64ObservableUpDownCounterOption) (metric.Int64ObservableUpDownCounter, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Int64ObservableGauge(name string, options ...metric.Int64ObservableGaugeOption) (metric.Int64ObservableGauge, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Float64Counter(name string, options ...metric.Float64CounterOption) (metric.Float64Counter, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Float64UpDownCounter(name string, options ...metric.Float64UpDownCounterOption) (metric.Float64UpDownCounter, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Float64Histogram(name string, options ...metric.Float64HistogramOption) (metric.Float64Histogram, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Float64Gauge(name string, options ...metric.Float64GaugeOption) (metric.Float64Gauge, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Float64ObservableCounter(name string, options ...metric.Float64ObservableCounterOption) (metric.Float64ObservableCounter, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Float64ObservableUpDownCounter(name string, options ...metric.Float64ObservableUpDownCounterOption) (metric.Float64ObservableUpDownCounter, error) {
+	return nil, nil
+}
+
+func (am *altMeter) Float64ObservableGauge(name string, options ...metric.Float64ObservableGaugeOption) (metric.Float64ObservableGauge, error) {
+	// Note: The global delegation also breaks when we return nil in one of these!
+	return nil, nil
+}
+
+func (am *altMeter) RegisterCallback(f metric.Callback, instruments ...metric.Observable) (metric.Registration, error) {
+	for _, inst := range instruments {
+		switch inst.(type) {
+		case *testAsyncCounter:
+			// OK!
+		default:
+			am.provider.t.Errorf("unexpected type %T", inst)
+		}
+	}
+	am.cbs = append(am.cbs, f)
+	return &altRegistration{cb: f}, nil
+}
+
+func (ao *altObserver) ObserveFloat64(inst metric.Float64Observable, _ float64, _ ...metric.ObserveOption) {
+	ao.observe(inst)
+}
+
+func (ao *altObserver) ObserveInt64(inst metric.Int64Observable, _ int64, _ ...metric.ObserveOption) {
+	ao.observe(inst)
+}
+
+func (ao *altObserver) observe(inst any) {
+	switch inst.(type) {
+	case *testAsyncCounter:
+		// OK!
+	default:
+		ao.t.Errorf("unexpected type %T", inst)
+	}
+}
+
+func TestMeterDelegation(t *testing.T) {
+	ResetForTest(t)
+
+	amp := &altMeterProvider{t: t}
+
+	gm := MeterProvider().Meter("test")
+	ai, err := gm.Int64ObservableCounter("test_counter")
+	require.NoError(t, err)
+
+	_, err = gm.RegisterCallback(func(_ context.Context, obs metric.Observer) error {
+		obs.ObserveInt64(ai, 10)
+		return nil
+	}, ai)
+	require.NoError(t, err)
+
+	SetMeterProvider(amp)
+
+	ctx := context.Background()
+	ao := &altObserver{t: t}
+	for _, meter := range amp.meters {
+		for _, cb := range meter.cbs {
+			require.NoError(t, cb(ctx, ao))
+		}
+	}
+}

internal/global/instruments.go

@@ -13,7 +13,7 @@ import (
 
 // unwrapper unwraps to return the underlying instrument implementation.
 type unwrapper interface {
-	Unwrap() metric.Observable
+	unwrap() metric.Observable
 }
 
 type afCounter struct {
@@ -40,7 +40,7 @@ func (i *afCounter) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *afCounter) Unwrap() metric.Observable {
+func (i *afCounter) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Float64ObservableCounter)
 	}
@@ -71,7 +71,7 @@ func (i *afUpDownCounter) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *afUpDownCounter) Unwrap() metric.Observable {
+func (i *afUpDownCounter) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Float64ObservableUpDownCounter)
 	}
@@ -102,7 +102,7 @@ func (i *afGauge) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *afGauge) Unwrap() metric.Observable {
+func (i *afGauge) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Float64ObservableGauge)
 	}
@@ -133,7 +133,7 @@ func (i *aiCounter) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *aiCounter) Unwrap() metric.Observable {
+func (i *aiCounter) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Int64ObservableCounter)
 	}
@@ -164,7 +164,7 @@ func (i *aiUpDownCounter) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *aiUpDownCounter) Unwrap() metric.Observable {
+func (i *aiUpDownCounter) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Int64ObservableUpDownCounter)
 	}
@@ -195,7 +195,7 @@ func (i *aiGauge) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *aiGauge) Unwrap() metric.Observable {
+func (i *aiGauge) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Int64ObservableGauge)
 	}

internal/global/instruments_test.go

@@ -57,19 +57,19 @@ func TestAsyncInstrumentSetDelegateConcurrentSafe(t *testing.T) {
 	t.Run("Float64", func(t *testing.T) {
 		t.Run("Counter", func(t *testing.T) {
 			delegate := &afCounter{}
-			f := func(float64) { _ = delegate.Unwrap() }
+			f := func(float64) { _ = delegate.unwrap() }
 			testFloat64ConcurrentSafe(f, delegate.setDelegate)
 		})
 
 		t.Run("UpDownCounter", func(t *testing.T) {
 			delegate := &afUpDownCounter{}
-			f := func(float64) { _ = delegate.Unwrap() }
+			f := func(float64) { _ = delegate.unwrap() }
 			testFloat64ConcurrentSafe(f, delegate.setDelegate)
 		})
 
 		t.Run("Gauge", func(t *testing.T) {
 			delegate := &afGauge{}
-			f := func(float64) { _ = delegate.Unwrap() }
+			f := func(float64) { _ = delegate.unwrap() }
 			testFloat64ConcurrentSafe(f, delegate.setDelegate)
 		})
 	})
@@ -79,19 +79,19 @@ func TestAsyncInstrumentSetDelegateConcurrentSafe(t *testing.T) {
 	t.Run("Int64", func(t *testing.T) {
 		t.Run("Counter", func(t *testing.T) {
 			delegate := &aiCounter{}
-			f := func(int64) { _ = delegate.Unwrap() }
+			f := func(int64) { _ = delegate.unwrap() }
 			testInt64ConcurrentSafe(f, delegate.setDelegate)
 		})
 
 		t.Run("UpDownCounter", func(t *testing.T) {
 			delegate := &aiUpDownCounter{}
-			f := func(int64) { _ = delegate.Unwrap() }
+			f := func(int64) { _ = delegate.unwrap() }
 			testInt64ConcurrentSafe(f, delegate.setDelegate)
 		})
 
 		t.Run("Gauge", func(t *testing.T) {
 			delegate := &aiGauge{}
-			f := func(int64) { _ = delegate.Unwrap() }
+			f := func(int64) { _ = delegate.unwrap() }
 			testInt64ConcurrentSafe(f, delegate.setDelegate)
 		})
 	})

internal/global/meter.go

@@ -5,6 +5,7 @@ package global // import "go.opentelemetry.io/otel/internal/global"
 
 import (
 	"container/list"
+	"context"
 	"reflect"
 	"sync"
 
@@ -472,8 +473,7 @@ func (m *meter) RegisterCallback(f metric.Callback, insts ...metric.Observable)
 	defer m.mtx.Unlock()
 
 	if m.delegate != nil {
-		insts = unwrapInstruments(insts)
-		return m.delegate.RegisterCallback(f, insts...)
+		return m.delegate.RegisterCallback(unwrapCallback(f), unwrapInstruments(insts)...)
 	}
 
 	reg := &registration{instruments: insts, function: f}
@@ -487,15 +487,11 @@ func (m *meter) RegisterCallback(f metric.Callback, insts ...metric.Observable)
 	return reg, nil
 }
 
-type wrapped interface {
-	unwrap() metric.Observable
-}
-
 func unwrapInstruments(instruments []metric.Observable) []metric.Observable {
 	out := make([]metric.Observable, 0, len(instruments))
 
 	for _, inst := range instruments {
-		if in, ok := inst.(wrapped); ok {
+		if in, ok := inst.(unwrapper); ok {
 			out = append(out, in.unwrap())
 		} else {
 			out = append(out, inst)
@@ -515,9 +511,33 @@ type registration struct {
 	unregMu sync.Mutex
 }
 
-func (c *registration) setDelegate(m metric.Meter) {
-	insts := unwrapInstruments(c.instruments)
+type unwrapObs struct {
+	embedded.Observer
+	obs metric.Observer
+}
+
+func (uo *unwrapObs) ObserveFloat64(inst metric.Float64Observable, value float64, opts ...metric.ObserveOption) {
+	if un, ok := inst.(unwrapper); ok {
+		inst = un.unwrap().(metric.Float64Observable)
+	}
+
+	uo.obs.ObserveFloat64(inst, value, opts...)
+}
 
+func (uo *unwrapObs) ObserveInt64(inst metric.Int64Observable, value int64, opts ...metric.ObserveOption) {
+	if un, ok := inst.(unwrapper); ok {
+		inst = un.unwrap().(metric.Int64Observable)
+	}
+	uo.obs.ObserveInt64(inst, value, opts...)
+}
+
+func unwrapCallback(f metric.Callback) metric.Callback {
+	return func(ctx context.Context, obs metric.Observer) error {
+		return f(ctx, &unwrapObs{obs: obs})
+	}
+}
+
+func (c *registration) setDelegate(m metric.Meter) {
 	c.unregMu.Lock()
 	defer c.unregMu.Unlock()
 
@@ -526,7 +546,7 @@ func (c *registration) setDelegate(m metric.Meter) {
 		return
 	}
 
-	reg, err := m.RegisterCallback(c.function, insts...)
+	reg, err := m.RegisterCallback(unwrapCallback(c.function), unwrapInstruments(c.instruments)...)
 	if err != nil {
 		GetErrorHandler().Handle(err)
 		return