Fix incorrect metrics getting generated from multiple readers (#5900)

Fixes https://github.com/open-telemetry/opentelemetry-go/issues/5866

---------

Co-authored-by: Robert Pająk <pellared@hotmail.com>

CHANGELOG.md

@@ -35,6 +35,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Fix `WithEndpointURL` to always use a secure connection when an https URL is passed in `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`. (#5944)
 - Fix `WithEndpointURL` to always use a secure connection when an https URL is passed in `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`. (#5944)
 - Fix `WithEndpointURL` to always use a secure connection when an https URL is passed in `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`. (#5944)
+- Fix incorrect metrics generated from callbacks when multiple readers are used in `go.opentelemetry.io/otel/sdk/metric`. (#5900)
 
 ### Changed
 

sdk/metric/meter.go

@@ -150,6 +150,11 @@ func (m *meter) int64ObservableInstrument(id Instrument, callbacks []metric.Int6
 				continue
 			}
 			inst.appendMeasures(in)
+
+			// Add the measures to the pipeline. It is required to maintain
+			// measures per pipeline to avoid calling the measure that
+			// is not part of the pipeline.
+			insert.pipeline.addInt64Measure(inst.observableID, in)
 			for _, cback := range callbacks {
 				inst := int64Observer{measures: in}
 				fn := cback
@@ -309,6 +314,11 @@ func (m *meter) float64ObservableInstrument(id Instrument, callbacks []metric.Fl
 				continue
 			}
 			inst.appendMeasures(in)
+
+			// Add the measures to the pipeline. It is required to maintain
+			// measures per pipeline to avoid calling the measure that
+			// is not part of the pipeline.
+			insert.pipeline.addFloat64Measure(inst.observableID, in)
 			for _, cback := range callbacks {
 				inst := float64Observer{measures: in}
 				fn := cback
@@ -441,8 +451,8 @@ func (m *meter) RegisterCallback(f metric.Callback, insts ...metric.Observable)
 		return noopRegister{}, nil
 	}
 
-	reg := newObserver()
 	var err error
+	validInstruments := make([]metric.Observable, 0, len(insts))
 	for _, inst := range insts {
 		switch o := inst.(type) {
 		case int64Observable:
@@ -452,7 +462,8 @@ func (m *meter) RegisterCallback(f metric.Callback, insts ...metric.Observable)
 				}
 				continue
 			}
-			reg.registerInt64(o.observableID)
+
+			validInstruments = append(validInstruments, inst)
 		case float64Observable:
 			if e := o.registerable(m); e != nil {
 				if !errors.Is(e, errEmptyAgg) {
@@ -460,41 +471,55 @@ func (m *meter) RegisterCallback(f metric.Callback, insts ...metric.Observable)
 				}
 				continue
 			}
-			reg.registerFloat64(o.observableID)
+
+			validInstruments = append(validInstruments, inst)
 		default:
 			// Instrument external to the SDK.
 			return nil, fmt.Errorf("invalid observable: from different implementation")
 		}
 	}
 
-	if reg.len() == 0 {
+	if len(validInstruments) == 0 {
 		// All insts use drop aggregation or are invalid.
 		return noopRegister{}, err
 	}
 
-	// Some or all instruments were valid.
-	cback := func(ctx context.Context) error { return f(ctx, reg) }
-	return m.pipes.registerMultiCallback(cback), err
+	unregs := make([]func(), len(m.pipes))
+	for ix, pipe := range m.pipes {
+		reg := newObserver(pipe)
+		for _, inst := range validInstruments {
+			switch o := inst.(type) {
+			case int64Observable:
+				reg.registerInt64(o.observableID)
+			case float64Observable:
+				reg.registerFloat64(o.observableID)
+			}
+		}
+
+		// Some or all instruments were valid.
+		cBack := func(ctx context.Context) error { return f(ctx, reg) }
+		unregs[ix] = pipe.addMultiCallback(cBack)
+	}
+
+	return unregisterFuncs{f: unregs}, err
 }
 
 type observer struct {
 	embedded.Observer
 
+	pipe    *pipeline
 	float64 map[observableID[float64]]struct{}
 	int64   map[observableID[int64]]struct{}
 }
 
-func newObserver() observer {
+func newObserver(p *pipeline) observer {
 	return observer{
+		pipe:    p,
 		float64: make(map[observableID[float64]]struct{}),
 		int64:   make(map[observableID[int64]]struct{}),
 	}
 }
 
-func (r observer) len() int {
-	return len(r.float64) + len(r.int64)
-}
-
 func (r observer) registerFloat64(id observableID[float64]) {
 	r.float64[id] = struct{}{}
 }
@@ -530,7 +555,12 @@ func (r observer) ObserveFloat64(o metric.Float64Observable, v float64, opts ...
 		return
 	}
 	c := metric.NewObserveConfig(opts)
-	oImpl.observe(v, c.Attributes())
+	// Access to r.pipe.float64Measure is already guarded by a lock in pipeline.produce.
+	// TODO (#5946): Refactor pipeline and observable measures.
+	measures := r.pipe.float64Measures[oImpl.observableID]
+	for _, m := range measures {
+		m(context.Background(), v, c.Attributes())
+	}
 }
 
 func (r observer) ObserveInt64(o metric.Int64Observable, v int64, opts ...metric.ObserveOption) {
@@ -555,7 +585,12 @@ func (r observer) ObserveInt64(o metric.Int64Observable, v int64, opts ...metric
 		return
 	}
 	c := metric.NewObserveConfig(opts)
-	oImpl.observe(v, c.Attributes())
+	// Access to r.pipe.int64Measures is already guarded b a lock in pipeline.produce.
+	// TODO (#5946): Refactor pipeline and observable measures.
+	measures := r.pipe.int64Measures[oImpl.observableID]
+	for _, m := range measures {
+		m(context.Background(), v, c.Attributes())
+	}
 }
 
 type noopRegister struct{ embedded.Registration }

sdk/metric/pipeline.go

@@ -12,7 +12,6 @@ import (
 	"sync/atomic"
 
 	"go.opentelemetry.io/otel/internal/global"
-	"go.opentelemetry.io/otel/metric"
 	"go.opentelemetry.io/otel/metric/embedded"
 	"go.opentelemetry.io/otel/sdk/instrumentation"
 	"go.opentelemetry.io/otel/sdk/metric/exemplar"
@@ -43,10 +42,12 @@ func newPipeline(res *resource.Resource, reader Reader, views []View, exemplarFi
 		res = resource.Empty()
 	}
 	return &pipeline{
-		resource:       res,
-		reader:         reader,
-		views:          views,
-		exemplarFilter: exemplarFilter,
+		resource:        res,
+		reader:          reader,
+		views:           views,
+		int64Measures:   map[observableID[int64]][]aggregate.Measure[int64]{},
+		float64Measures: map[observableID[float64]][]aggregate.Measure[float64]{},
+		exemplarFilter:  exemplarFilter,
 		// aggregations is lazy allocated when needed.
 	}
 }
@@ -64,10 +65,26 @@ type pipeline struct {
 	views  []View
 
 	sync.Mutex
-	aggregations   map[instrumentation.Scope][]instrumentSync
-	callbacks      []func(context.Context) error
-	multiCallbacks list.List
-	exemplarFilter exemplar.Filter
+	int64Measures   map[observableID[int64]][]aggregate.Measure[int64]
+	float64Measures map[observableID[float64]][]aggregate.Measure[float64]
+	aggregations    map[instrumentation.Scope][]instrumentSync
+	callbacks       []func(context.Context) error
+	multiCallbacks  list.List
+	exemplarFilter  exemplar.Filter
+}
+
+// addInt64Measure adds a new int64 measure to the pipeline for each observer.
+func (p *pipeline) addInt64Measure(id observableID[int64], m []aggregate.Measure[int64]) {
+	p.Lock()
+	defer p.Unlock()
+	p.int64Measures[id] = m
+}
+
+// addFloat64Measure adds a new float64 measure to the pipeline for each observer.
+func (p *pipeline) addFloat64Measure(id observableID[float64], m []aggregate.Measure[float64]) {
+	p.Lock()
+	defer p.Unlock()
+	p.float64Measures[id] = m
 }
 
 // addSync adds the instrumentSync to pipeline p with scope. This method is not
@@ -574,14 +591,6 @@ func newPipelines(res *resource.Resource, readers []Reader, views []View, exempl
 	return pipes
 }
 
-func (p pipelines) registerMultiCallback(c multiCallback) metric.Registration {
-	unregs := make([]func(), len(p))
-	for i, pipe := range p {
-		unregs[i] = pipe.addMultiCallback(c)
-	}
-	return unregisterFuncs{f: unregs}
-}
-
 type unregisterFuncs struct {
 	embedded.Registration
 	f []func()

sdk/metric/pipeline_test.go

@@ -11,6 +11,7 @@ import (
 	"runtime"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"testing"
 
 	"github.com/go-logr/logr"
@@ -24,6 +25,7 @@ import (
 	"go.opentelemetry.io/otel/metric"
 	"go.opentelemetry.io/otel/sdk/instrumentation"
 	"go.opentelemetry.io/otel/sdk/metric/exemplar"
+	"go.opentelemetry.io/otel/sdk/metric/internal/aggregate"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest"
 	"go.opentelemetry.io/otel/sdk/resource"
@@ -101,6 +103,21 @@ func TestPipelineConcurrentSafe(t *testing.T) {
 			defer wg.Done()
 			pipe.addMultiCallback(func(context.Context) error { return nil })
 		}()
+
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			b := aggregate.Builder[int64]{
+				Temporality:      metricdata.CumulativeTemporality,
+				ReservoirFunc:    nil,
+				AggregationLimit: 0,
+			}
+			var oID observableID[int64]
+			m, _ := b.PrecomputedSum(false)
+			measures := []aggregate.Measure[int64]{}
+			measures = append(measures, m)
+			pipe.addInt64Measure(oID, measures)
+		}()
 	}
 	wg.Wait()
 }
@@ -518,3 +535,81 @@ func TestExemplars(t *testing.T) {
 		check(t, r, 2, 2, 2)
 	})
 }
+
+func TestAddingAndObservingMeasureConcurrentSafe(t *testing.T) {
+	r1 := NewManualReader()
+	r2 := NewManualReader()
+
+	mp := NewMeterProvider(WithReader(r1), WithReader(r2))
+	m := mp.Meter("test")
+
+	oc1, err := m.Int64ObservableCounter("int64-observable-counter")
+	require.NoError(t, err)
+
+	wg := sync.WaitGroup{}
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		_, err := m.Int64ObservableCounter("int64-observable-counter-2")
+		require.NoError(t, err)
+	}()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		_, err := m.RegisterCallback(
+			func(_ context.Context, o metric.Observer) error {
+				o.ObserveInt64(oc1, 2)
+				return nil
+			}, oc1)
+		require.NoError(t, err)
+	}()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		_ = mp.pipes[0].produce(context.Background(), &metricdata.ResourceMetrics{})
+	}()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		_ = mp.pipes[1].produce(context.Background(), &metricdata.ResourceMetrics{})
+	}()
+
+	wg.Wait()
+}
+
+func TestPipelineWithMultipleReaders(t *testing.T) {
+	r1 := NewManualReader()
+	r2 := NewManualReader()
+	mp := NewMeterProvider(WithReader(r1), WithReader(r2))
+	m := mp.Meter("test")
+	var val atomic.Int64
+	oc, err := m.Int64ObservableCounter("int64-observable-counter")
+	require.NoError(t, err)
+	reg, err := m.RegisterCallback(
+		// SDK calls this function when collecting data.
+		func(_ context.Context, o metric.Observer) error {
+			o.ObserveInt64(oc, val.Load())
+			return nil
+		}, oc)
+	require.NoError(t, err)
+	t.Cleanup(func() { assert.NoError(t, reg.Unregister()) })
+	ctx := context.Background()
+	rm := new(metricdata.ResourceMetrics)
+	val.Add(1)
+	err = r1.Collect(ctx, rm)
+	require.NoError(t, err)
+	if assert.Len(t, rm.ScopeMetrics, 1) &&
+		assert.Len(t, rm.ScopeMetrics[0].Metrics, 1) {
+		assert.Equal(t, int64(1), rm.ScopeMetrics[0].Metrics[0].Data.(metricdata.Sum[int64]).DataPoints[0].Value)
+	}
+	val.Add(1)
+	err = r2.Collect(ctx, rm)
+	require.NoError(t, err)
+	if assert.Len(t, rm.ScopeMetrics, 1) &&
+		assert.Len(t, rm.ScopeMetrics[0].Metrics, 1) {
+		assert.Equal(t, int64(2), rm.ScopeMetrics[0].Metrics[0].Data.(metricdata.Sum[int64]).DataPoints[0].Value)
+	}
+}