prototype for metric.Producer as an argument to Reader

example/opencensus/main.go

@@ -103,9 +103,8 @@ func tracing(otExporter sdktrace.SpanExporter) {
 // registry or an OpenCensus view.
 func monitoring(exporter metric.Exporter) error {
 	log.Println("Adding the OpenCensus metric Producer to an OpenTelemetry Reader to export OpenCensus metrics using the OpenTelemetry stdout exporter.")
-	reader := metric.NewPeriodicReader(exporter)
 	// Register the OpenCensus metric Producer to add metrics from OpenCensus to the output.
-	reader.RegisterProducer(opencensus.NewMetricProducer())
+	reader := metric.NewPeriodicReader(exporter, metric.WithProducer(opencensus.NewMetricProducer()))
 	metric.NewMeterProvider(metric.WithReader(reader))
 
 	log.Println("Registering a gauge metric using an OpenCensus registry.")

sdk/metric/manual_reader.go

@@ -34,7 +34,7 @@ type ManualReader struct {
 
 	mu                sync.Mutex
 	isShutdown        bool
-	externalProducers atomic.Value
+	externalProducers []Producer
 
 	temporalitySelector TemporalitySelector
 	aggregationSelector AggregationSelector
@@ -49,8 +49,8 @@ func NewManualReader(opts ...ManualReaderOption) *ManualReader {
 	r := &ManualReader{
 		temporalitySelector: cfg.temporalitySelector,
 		aggregationSelector: cfg.aggregationSelector,
+		externalProducers:   cfg.producers,
 	}
-	r.externalProducers.Store([]Producer{})
 	return r
 }
 
@@ -64,23 +64,6 @@ func (mr *ManualReader) register(p sdkProducer) {
 	}
 }
 
-// RegisterProducer stores the external Producer which enables the caller
-// to read metrics on demand.
-//
-// This method is safe to call concurrently.
-func (mr *ManualReader) RegisterProducer(p Producer) {
-	mr.mu.Lock()
-	defer mr.mu.Unlock()
-	if mr.isShutdown {
-		return
-	}
-	currentProducers := mr.externalProducers.Load().([]Producer)
-	newProducers := []Producer{}
-	newProducers = append(newProducers, currentProducers...)
-	newProducers = append(newProducers, p)
-	mr.externalProducers.Store(newProducers)
-}
-
 // temporality reports the Temporality for the instrument kind provided.
 func (mr *ManualReader) temporality(kind InstrumentKind) metricdata.Temporality {
 	return mr.temporalitySelector(kind)
@@ -112,7 +95,7 @@ func (mr *ManualReader) Shutdown(context.Context) error {
 		defer mr.mu.Unlock()
 		mr.isShutdown = true
 		// release references to Producer(s)
-		mr.externalProducers.Store([]Producer{})
+		mr.externalProducers = nil
 		err = nil
 	})
 	return err
@@ -150,7 +133,7 @@ func (mr *ManualReader) Collect(ctx context.Context, rm *metricdata.ResourceMetr
 		return err
 	}
 	var errs []error
-	for _, producer := range mr.externalProducers.Load().([]Producer) {
+	for _, producer := range mr.externalProducers {
 		externalMetrics, err := producer.Produce(ctx)
 		if err != nil {
 			errs = append(errs, err)
@@ -183,6 +166,7 @@ func (r *ManualReader) MarshalLog() interface{} {
 type manualReaderConfig struct {
 	temporalitySelector TemporalitySelector
 	aggregationSelector AggregationSelector
+	producers           []Producer
 }
 
 // newManualReaderConfig returns a manualReaderConfig configured with options.

sdk/metric/manual_reader_test.go

@@ -27,7 +27,13 @@ import (
 )
 
 func TestManualReader(t *testing.T) {
-	suite.Run(t, &readerTestSuite{Factory: func() Reader { return NewManualReader() }})
+	suite.Run(t, &readerTestSuite{Factory: func(opts ...ReaderOption) Reader {
+		var mopts []ManualReaderOption
+		for _, o := range opts {
+			mopts = append(mopts, o)
+		}
+		return NewManualReader(mopts...)
+	}})
 }
 
 func BenchmarkManualReader(b *testing.B) {

sdk/metric/periodic_reader.go

@@ -36,8 +36,9 @@ const (
 
 // periodicReaderConfig contains configuration options for a PeriodicReader.
 type periodicReaderConfig struct {
-	interval time.Duration
-	timeout  time.Duration
+	interval  time.Duration
+	timeout   time.Duration
+	producers []Producer
 }
 
 // newPeriodicReaderConfig returns a periodicReaderConfig configured with
@@ -115,18 +116,18 @@ func NewPeriodicReader(exporter Exporter, options ...PeriodicReaderOption) *Peri
 	conf := newPeriodicReaderConfig(options)
 	ctx, cancel := context.WithCancel(context.Background())
 	r := &PeriodicReader{
-		interval: conf.interval,
-		timeout:  conf.timeout,
-		exporter: exporter,
-		flushCh:  make(chan chan error),
-		cancel:   cancel,
-		done:     make(chan struct{}),
+		interval:          conf.interval,
+		timeout:           conf.timeout,
+		exporter:          exporter,
+		flushCh:           make(chan chan error),
+		cancel:            cancel,
+		done:              make(chan struct{}),
+		externalProducers: conf.producers,
 		rmPool: sync.Pool{
 			New: func() interface{} {
 				return &metricdata.ResourceMetrics{}
 			}},
 	}
-	r.externalProducers.Store([]Producer{})
 
 	go func() {
 		defer func() { close(r.done) }()
@@ -143,7 +144,7 @@ type PeriodicReader struct {
 
 	mu                sync.Mutex
 	isShutdown        bool
-	externalProducers atomic.Value
+	externalProducers []Producer
 
 	interval time.Duration
 	timeout  time.Duration
@@ -194,22 +195,6 @@ func (r *PeriodicReader) register(p sdkProducer) {
 	}
 }
 
-// RegisterProducer registers p as an external Producer of this reader.
-//
-// This method is safe to call concurrently.
-func (r *PeriodicReader) RegisterProducer(p Producer) {
-	r.mu.Lock()
-	defer r.mu.Unlock()
-	if r.isShutdown {
-		return
-	}
-	currentProducers := r.externalProducers.Load().([]Producer)
-	newProducers := []Producer{}
-	newProducers = append(newProducers, currentProducers...)
-	newProducers = append(newProducers, p)
-	r.externalProducers.Store(newProducers)
-}
-
 // temporality reports the Temporality for the instrument kind provided.
 func (r *PeriodicReader) temporality(kind InstrumentKind) metricdata.Temporality {
 	return r.exporter.Temporality(kind)
@@ -275,7 +260,7 @@ func (r *PeriodicReader) collect(ctx context.Context, p interface{}, rm *metricd
 		return err
 	}
 	var errs []error
-	for _, producer := range r.externalProducers.Load().([]Producer) {
+	for _, producer := range r.externalProducers {
 		externalMetrics, err := producer.Produce(ctx)
 		if err != nil {
 			errs = append(errs, err)
@@ -351,7 +336,7 @@ func (r *PeriodicReader) Shutdown(ctx context.Context) error {
 		defer r.mu.Unlock()
 		r.isShutdown = true
 		// release references to Producer(s)
-		r.externalProducers.Store([]Producer{})
+		r.externalProducers = nil
 	})
 	return err
 }

sdk/metric/periodic_reader_test.go

@@ -202,17 +202,16 @@ type periodicReaderTestSuite struct {
 }
 
 func (ts *periodicReaderTestSuite) SetupTest() {
-	ts.readerTestSuite.SetupTest()
+	ts.Reader = ts.Factory()
 
 	e := &fnExporter{
 		exportFunc:   func(context.Context, *metricdata.ResourceMetrics) error { return assert.AnError },
 		flushFunc:    func(context.Context) error { return assert.AnError },
 		shutdownFunc: func(context.Context) error { return assert.AnError },
 	}
 
-	ts.ErrReader = NewPeriodicReader(e)
+	ts.ErrReader = NewPeriodicReader(e, WithProducer(testExternalProducer{}))
 	ts.ErrReader.register(testSDKProducer{})
-	ts.ErrReader.RegisterProducer(testExternalProducer{})
 }
 
 func (ts *periodicReaderTestSuite) TearDownTest() {
@@ -232,8 +231,12 @@ func (ts *periodicReaderTestSuite) TestShutdownPropagated() {
 func TestPeriodicReader(t *testing.T) {
 	suite.Run(t, &periodicReaderTestSuite{
 		readerTestSuite: &readerTestSuite{
-			Factory: func() Reader {
-				return NewPeriodicReader(new(fnExporter))
+			Factory: func(opts ...ReaderOption) Reader {
+				var popts []PeriodicReaderOption
+				for _, o := range opts {
+					popts = append(popts, o)
+				}
+				return NewPeriodicReader(new(fnExporter), popts...)
 			},
 		},
 	})
@@ -290,9 +293,8 @@ func TestPeriodicReaderRun(t *testing.T) {
 		},
 	}
 
-	r := NewPeriodicReader(exp)
+	r := NewPeriodicReader(exp, WithProducer(testExternalProducer{}))
 	r.register(testSDKProducer{})
-	r.RegisterProducer(testExternalProducer{})
 	trigger <- time.Now()
 	assert.Equal(t, assert.AnError, <-eh.Err)
 
@@ -319,9 +321,8 @@ func TestPeriodicReaderFlushesPending(t *testing.T) {
 
 	t.Run("ForceFlush", func(t *testing.T) {
 		exp, called := expFunc(t)
-		r := NewPeriodicReader(exp)
+		r := NewPeriodicReader(exp, WithProducer(testExternalProducer{}))
 		r.register(testSDKProducer{})
-		r.RegisterProducer(testExternalProducer{})
 		assert.Equal(t, assert.AnError, r.ForceFlush(context.Background()), "export error not returned")
 		assert.True(t, *called, "exporter Export method not called, pending telemetry not flushed")
 
@@ -331,9 +332,8 @@ func TestPeriodicReaderFlushesPending(t *testing.T) {
 
 	t.Run("Shutdown", func(t *testing.T) {
 		exp, called := expFunc(t)
-		r := NewPeriodicReader(exp)
+		r := NewPeriodicReader(exp, WithProducer(testExternalProducer{}))
 		r.register(testSDKProducer{})
-		r.RegisterProducer(testExternalProducer{})
 		assert.Equal(t, assert.AnError, r.Shutdown(context.Background()), "export error not returned")
 		assert.True(t, *called, "exporter Export method not called, pending telemetry not flushed")
 	})

sdk/metric/reader.go

@@ -57,13 +57,6 @@ type Reader interface {
 	// and send aggregated metric measurements.
 	register(sdkProducer)
 
-	// RegisterProducer registers a an external Producer with this Reader.
-	// The Producer is used as a source of aggregated metric data which is
-	// incorporated into metrics collected from the SDK.
-	//
-	// This method needs to be concurrent safe.
-	RegisterProducer(Producer)
-
 	// temporality reports the Temporality for the instrument kind provided.
 	temporality(InstrumentKind) metricdata.Temporality
 
@@ -167,3 +160,32 @@ func DefaultAggregationSelector(ik InstrumentKind) aggregation.Aggregation {
 	}
 	panic("unknown instrument kind")
 }
+
+// ReaderOption is an option which can be applied to manual or Periodic
+// readers.
+type ReaderOption interface {
+	PeriodicReaderOption
+	ManualReaderOption
+}
+
+// WithProducers registers producers as an external Producer of metric data
+// for this Reader.
+func WithProducer(p Producer) ReaderOption {
+	return producerOption{p: p}
+}
+
+type producerOption struct {
+	p Producer
+}
+
+// applyManual returns a manualReaderConfig with option applied.
+func (o producerOption) applyManual(c manualReaderConfig) manualReaderConfig {
+	c.producers = append(c.producers, o.p)
+	return c
+}
+
+// applyPeriodic returns a periodicReaderConfig with option applied.
+func (o producerOption) applyPeriodic(c periodicReaderConfig) periodicReaderConfig {
+	c.producers = append(c.producers, o.p)
+	return c
+}