Update the metric Export interface to accept a *ResourceMetrics instead of ResourceMetrics (#3853)

* Change the signature of Export method

* Pass tests for otlp exporter

* Pass tests for otlp grpc and http packages

* Update opencensus bridge

* Refactor and pass tests for stdoutmetric package

* Update periodic reader tests

* Update changelog

* Apply suggestions

* Apply suggestions

* Update CHANGELOG.md

---------

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -21,6 +21,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Avoid creating new objects on all calls to `WithDeferredSetup` and `SkipContextSetup` in OpenTracing bridge. (#3833)
 - The `New` and `Detect` functions from `go.opentelemetry.io/otel/sdk/resource` return errors that wrap underlying errors instead of just containing the underlying error strings. (#3844)
 - Both the `Histogram` and `HistogramDataPoint` are redefined with a generic argument of `[N int64 | float64]` in `go.opentelemetry.io/otel/sdk/metric/metricdata`. (#3849)
+- The metric `Export` interface from `go.opentelemetry.io/otel/sdk/metric` accepts a `*ResourceMetrics` instead of `ResourceMetrics`. (#3853)
 
 ### Removed
 

bridge/opencensus/metric.go

@@ -85,7 +85,7 @@ func (e *exporter) ExportMetrics(ctx context.Context, ocmetrics []*ocmetricdata.
 	if len(otelmetrics) == 0 {
 		return nil
 	}
-	return e.base.Export(ctx, metricdata.ResourceMetrics{
+	return e.base.Export(ctx, &metricdata.ResourceMetrics{
 		Resource: e.res,
 		ScopeMetrics: []metricdata.ScopeMetrics{
 			{

bridge/opencensus/metric_test.go

@@ -278,9 +278,9 @@ type fakeExporter struct {
 	err  error
 }
 
-func (f *fakeExporter) Export(ctx context.Context, data metricdata.ResourceMetrics) error {
+func (f *fakeExporter) Export(ctx context.Context, data *metricdata.ResourceMetrics) error {
 	if f.err == nil {
-		f.data = &data
+		f.data = data
 	}
 	return f.err
 }

exporters/otlp/otlpmetric/internal/exporter.go

@@ -50,7 +50,7 @@ func (e *exporter) Aggregation(k metric.InstrumentKind) aggregation.Aggregation
 }
 
 // Export transforms and transmits metric data to an OTLP receiver.
-func (e *exporter) Export(ctx context.Context, rm metricdata.ResourceMetrics) error {
+func (e *exporter) Export(ctx context.Context, rm *metricdata.ResourceMetrics) error {
 	otlpRm, err := transform.ResourceMetrics(rm)
 	// Best effort upload of transformable metrics.
 	e.clientMu.Lock()

exporters/otlp/otlpmetric/internal/exporter_test.go

@@ -60,7 +60,7 @@ func TestExporterClientConcurrency(t *testing.T) {
 	const goroutines = 5
 
 	exp := New(&client{})
-	rm := metricdata.ResourceMetrics{}
+	rm := new(metricdata.ResourceMetrics)
 	ctx := context.Background()
 
 	done := make(chan struct{})

exporters/otlp/otlpmetric/internal/transform/metricdata.go

@@ -26,7 +26,7 @@ import (
 // ResourceMetrics returns an OTLP ResourceMetrics generated from rm. If rm
 // contains invalid ScopeMetrics, an error will be returned along with an OTLP
 // ResourceMetrics that contains partial OTLP ScopeMetrics.
-func ResourceMetrics(rm metricdata.ResourceMetrics) (*mpb.ResourceMetrics, error) {
+func ResourceMetrics(rm *metricdata.ResourceMetrics) (*mpb.ResourceMetrics, error) {
 	sms, err := ScopeMetrics(rm.ScopeMetrics)
 	return &mpb.ResourceMetrics{
 		Resource: &rpb.Resource{

exporters/otlp/otlpmetric/internal/transform/metricdata_test.go

@@ -345,7 +345,7 @@ var (
 		},
 	}
 
-	otelResourceMetrics = metricdata.ResourceMetrics{
+	otelResourceMetrics = &metricdata.ResourceMetrics{
 		Resource:     otelRes,
 		ScopeMetrics: otelScopeMetrics,
 	}

exporters/otlp/otlpmetric/otlpmetricgrpc/client_test.go

@@ -165,7 +165,7 @@ func TestConfig(t *testing.T) {
 		exp, coll := factoryFunc(nil, WithHeaders(headers))
 		t.Cleanup(coll.Shutdown)
 		ctx := context.Background()
-		require.NoError(t, exp.Export(ctx, metricdata.ResourceMetrics{}))
+		require.NoError(t, exp.Export(ctx, &metricdata.ResourceMetrics{}))
 		// Ensure everything is flushed.
 		require.NoError(t, exp.Shutdown(ctx))
 
@@ -187,7 +187,7 @@ func TestConfig(t *testing.T) {
 		t.Cleanup(coll.Shutdown)
 		ctx := context.Background()
 		t.Cleanup(func() { require.NoError(t, exp.Shutdown(ctx)) })
-		err := exp.Export(ctx, metricdata.ResourceMetrics{})
+		err := exp.Export(ctx, &metricdata.ResourceMetrics{})
 		assert.ErrorContains(t, err, context.DeadlineExceeded.Error())
 	})
 
@@ -197,7 +197,7 @@ func TestConfig(t *testing.T) {
 		exp, coll := factoryFunc(nil, WithDialOption(grpc.WithUserAgent(customerUserAgent)))
 		t.Cleanup(coll.Shutdown)
 		ctx := context.Background()
-		require.NoError(t, exp.Export(ctx, metricdata.ResourceMetrics{}))
+		require.NoError(t, exp.Export(ctx, &metricdata.ResourceMetrics{}))
 		// Ensure everything is flushed.
 		require.NoError(t, exp.Shutdown(ctx))
 

exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go

@@ -70,7 +70,7 @@ func TestConfig(t *testing.T) {
 		exp, coll := factoryFunc("", nil, WithHeaders(headers))
 		ctx := context.Background()
 		t.Cleanup(func() { require.NoError(t, coll.Shutdown(ctx)) })
-		require.NoError(t, exp.Export(ctx, metricdata.ResourceMetrics{}))
+		require.NoError(t, exp.Export(ctx, &metricdata.ResourceMetrics{}))
 		// Ensure everything is flushed.
 		require.NoError(t, exp.Shutdown(ctx))
 
@@ -94,7 +94,7 @@ func TestConfig(t *testing.T) {
 		// Push this after Shutdown so the HTTP server doesn't hang.
 		t.Cleanup(func() { close(rCh) })
 		t.Cleanup(func() { require.NoError(t, exp.Shutdown(ctx)) })
-		err := exp.Export(ctx, metricdata.ResourceMetrics{})
+		err := exp.Export(ctx, &metricdata.ResourceMetrics{})
 		assert.ErrorContains(t, err, context.DeadlineExceeded.Error())
 	})
 
@@ -103,7 +103,7 @@ func TestConfig(t *testing.T) {
 		ctx := context.Background()
 		t.Cleanup(func() { require.NoError(t, coll.Shutdown(ctx)) })
 		t.Cleanup(func() { require.NoError(t, exp.Shutdown(ctx)) })
-		assert.NoError(t, exp.Export(ctx, metricdata.ResourceMetrics{}))
+		assert.NoError(t, exp.Export(ctx, &metricdata.ResourceMetrics{}))
 		assert.Len(t, coll.Collect().Dump(), 1)
 	})
 
@@ -133,7 +133,7 @@ func TestConfig(t *testing.T) {
 		// Push this after Shutdown so the HTTP server doesn't hang.
 		t.Cleanup(func() { close(rCh) })
 		t.Cleanup(func() { require.NoError(t, exp.Shutdown(ctx)) })
-		assert.NoError(t, exp.Export(ctx, metricdata.ResourceMetrics{}), "failed retry")
+		assert.NoError(t, exp.Export(ctx, &metricdata.ResourceMetrics{}), "failed retry")
 		assert.Len(t, rCh, 0, "failed HTTP responses did not occur")
 	})
 
@@ -144,7 +144,7 @@ func TestConfig(t *testing.T) {
 		ctx := context.Background()
 		t.Cleanup(func() { require.NoError(t, coll.Shutdown(ctx)) })
 		t.Cleanup(func() { require.NoError(t, exp.Shutdown(ctx)) })
-		assert.NoError(t, exp.Export(ctx, metricdata.ResourceMetrics{}))
+		assert.NoError(t, exp.Export(ctx, &metricdata.ResourceMetrics{}))
 		assert.Len(t, coll.Collect().Dump(), 1)
 	})
 
@@ -155,7 +155,7 @@ func TestConfig(t *testing.T) {
 		ctx := context.Background()
 		t.Cleanup(func() { require.NoError(t, coll.Shutdown(ctx)) })
 		t.Cleanup(func() { require.NoError(t, exp.Shutdown(ctx)) })
-		assert.NoError(t, exp.Export(ctx, metricdata.ResourceMetrics{}))
+		assert.NoError(t, exp.Export(ctx, &metricdata.ResourceMetrics{}))
 		assert.Len(t, coll.Collect().Dump(), 1)
 	})
 
@@ -166,7 +166,7 @@ func TestConfig(t *testing.T) {
 		ctx := context.Background()
 		t.Cleanup(func() { require.NoError(t, coll.Shutdown(ctx)) })
 		t.Cleanup(func() { require.NoError(t, exp.Shutdown(ctx)) })
-		assert.NoError(t, exp.Export(ctx, metricdata.ResourceMetrics{}))
+		assert.NoError(t, exp.Export(ctx, &metricdata.ResourceMetrics{}))
 		assert.Len(t, coll.Collect().Dump(), 1)
 	})
 
@@ -176,7 +176,7 @@ func TestConfig(t *testing.T) {
 		exp, coll := factoryFunc("", nil, WithHeaders(headers))
 		ctx := context.Background()
 		t.Cleanup(func() { require.NoError(t, coll.Shutdown(ctx)) })
-		require.NoError(t, exp.Export(ctx, metricdata.ResourceMetrics{}))
+		require.NoError(t, exp.Export(ctx, &metricdata.ResourceMetrics{}))
 		// Ensure everything is flushed.
 		require.NoError(t, exp.Shutdown(ctx))
 

exporters/stdout/stdoutmetric/example_test.go

@@ -153,7 +153,7 @@ func Example() {
 	// This is where the sdk would be used to create a Meter and from that
 	// instruments that would make measurements of your code. To simulate that
 	// behavior, call export directly with mocked data.
-	_ = exp.Export(ctx, mockData)
+	_ = exp.Export(ctx, &mockData)
 
 	// Ensure the periodic reader is cleaned up by shutting down the sdk.
 	_ = sdk.Shutdown(ctx)
@@ -325,6 +325,6 @@ func Example() {
 	//       }
 	//     }
 	//   ],
-	//   "ScopeMetrics": []
+	//   "ScopeMetrics": null
 	// }
 }

exporters/stdout/stdoutmetric/exporter.go

@@ -62,7 +62,7 @@ func (e *exporter) Aggregation(k metric.InstrumentKind) aggregation.Aggregation
 	return e.aggregationSelector(k)
 }
 
-func (e *exporter) Export(ctx context.Context, data metricdata.ResourceMetrics) error {
+func (e *exporter) Export(ctx context.Context, data *metricdata.ResourceMetrics) error {
 	select {
 	case <-ctx.Done():
 		// Don't do anything if the context has already timed out.
@@ -71,7 +71,7 @@ func (e *exporter) Export(ctx context.Context, data metricdata.ResourceMetrics)
 		// Context is still valid, continue.
 	}
 	if e.redactTimestamps {
-		data = redactTimestamps(data)
+		redactTimestamps(data)
 	}
 	return e.encVal.Load().(encoderHolder).Encode(data)
 }
@@ -90,26 +90,14 @@ func (e *exporter) Shutdown(ctx context.Context) error {
 	return ctx.Err()
 }
 
-func redactTimestamps(orig metricdata.ResourceMetrics) metricdata.ResourceMetrics {
-	rm := metricdata.ResourceMetrics{
-		Resource:     orig.Resource,
-		ScopeMetrics: make([]metricdata.ScopeMetrics, len(orig.ScopeMetrics)),
-	}
+func redactTimestamps(orig *metricdata.ResourceMetrics) {
 	for i, sm := range orig.ScopeMetrics {
-		rm.ScopeMetrics[i] = metricdata.ScopeMetrics{
-			Scope:   sm.Scope,
-			Metrics: make([]metricdata.Metrics, len(sm.Metrics)),
-		}
-		for j, m := range sm.Metrics {
-			rm.ScopeMetrics[i].Metrics[j] = metricdata.Metrics{
-				Name:        m.Name,
-				Description: m.Description,
-				Unit:        m.Unit,
-				Data:        redactAggregationTimestamps(m.Data),
-			}
+		metrics := sm.Metrics
+		for j, m := range metrics {
+			data := m.Data
+			orig.ScopeMetrics[i].Metrics[j].Data = redactAggregationTimestamps(data)
 		}
 	}
-	return rm
 }
 
 var (

exporters/stdout/stdoutmetric/exporter_test.go

@@ -83,7 +83,7 @@ func TestExporterHonorsContextErrors(t *testing.T) {
 		exp, err := stdoutmetric.New(testEncoderOption())
 		require.NoError(t, err)
 		return func(ctx context.Context) error {
-			var data metricdata.ResourceMetrics
+			data := new(metricdata.ResourceMetrics)
 			return exp.Export(ctx, data)
 		}
 	}))
@@ -91,7 +91,7 @@ func TestExporterHonorsContextErrors(t *testing.T) {
 
 func TestShutdownExporterReturnsShutdownErrorOnExport(t *testing.T) {
 	var (
-		data     metricdata.ResourceMetrics
+		data     = new(metricdata.ResourceMetrics)
 		ctx      = context.Background()
 		exp, err = stdoutmetric.New(testEncoderOption())
 	)

sdk/metric/exporter.go

@@ -49,7 +49,7 @@ type Exporter interface {
 	// The passed ResourceMetrics may be reused when the call completes. If an
 	// exporter needs to hold this data after it returns, it needs to make a
 	// copy.
-	Export(context.Context, metricdata.ResourceMetrics) error
+	Export(context.Context, *metricdata.ResourceMetrics) error
 
 	// ForceFlush flushes any metric data held by an exporter.
 	//

sdk/metric/periodic_reader.go

@@ -223,7 +223,7 @@ func (r *periodicReader) collectAndExport(ctx context.Context) error {
 	rm := r.rmPool.Get().(*metricdata.ResourceMetrics)
 	err := r.Collect(ctx, rm)
 	if err == nil {
-		err = r.export(ctx, *rm)
+		err = r.export(ctx, rm)
 	}
 	r.rmPool.Put(rm)
 	return err
@@ -275,7 +275,7 @@ func (r *periodicReader) collect(ctx context.Context, p interface{}, rm *metricd
 }
 
 // export exports metric data m using r's exporter.
-func (r *periodicReader) export(ctx context.Context, m metricdata.ResourceMetrics) error {
+func (r *periodicReader) export(ctx context.Context, m *metricdata.ResourceMetrics) error {
 	c, cancel := context.WithTimeout(ctx, r.timeout)
 	defer cancel()
 	return r.exporter.Export(c, m)
@@ -321,7 +321,7 @@ func (r *periodicReader) Shutdown(ctx context.Context) error {
 			m := r.rmPool.Get().(*metricdata.ResourceMetrics)
 			err = r.collect(ctx, ph, m)
 			if err == nil {
-				err = r.export(ctx, *m)
+				err = r.export(ctx, m)
 			}
 			r.rmPool.Put(m)
 		}

sdk/metric/periodic_reader_test.go

@@ -152,7 +152,7 @@ func TestIntervalEnvAndOption(t *testing.T) {
 type fnExporter struct {
 	temporalityFunc TemporalitySelector
 	aggregationFunc AggregationSelector
-	exportFunc      func(context.Context, metricdata.ResourceMetrics) error
+	exportFunc      func(context.Context, *metricdata.ResourceMetrics) error
 	flushFunc       func(context.Context) error
 	shutdownFunc    func(context.Context) error
 }
@@ -173,7 +173,7 @@ func (e *fnExporter) Aggregation(k InstrumentKind) aggregation.Aggregation {
 	return DefaultAggregationSelector(k)
 }
 
-func (e *fnExporter) Export(ctx context.Context, m metricdata.ResourceMetrics) error {
+func (e *fnExporter) Export(ctx context.Context, m *metricdata.ResourceMetrics) error {
 	if e.exportFunc != nil {
 		return e.exportFunc(ctx, m)
 	}
@@ -204,7 +204,7 @@ func (ts *periodicReaderTestSuite) SetupTest() {
 	ts.readerTestSuite.SetupTest()
 
 	e := &fnExporter{
-		exportFunc:   func(context.Context, metricdata.ResourceMetrics) error { return assert.AnError },
+		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 },
 	}
@@ -282,9 +282,9 @@ func TestPeriodicReaderRun(t *testing.T) {
 	otel.SetErrorHandler(eh)
 
 	exp := &fnExporter{
-		exportFunc: func(_ context.Context, m metricdata.ResourceMetrics) error {
+		exportFunc: func(_ context.Context, m *metricdata.ResourceMetrics) error {
 			// The testSDKProducer produces testResourceMetricsAB.
-			assert.Equal(t, testResourceMetricsAB, m)
+			assert.Equal(t, testResourceMetricsAB, *m)
 			return assert.AnError
 		},
 	}
@@ -307,9 +307,9 @@ func TestPeriodicReaderFlushesPending(t *testing.T) {
 	expFunc := func(t *testing.T) (exp Exporter, called *bool) {
 		called = new(bool)
 		return &fnExporter{
-			exportFunc: func(_ context.Context, m metricdata.ResourceMetrics) error {
+			exportFunc: func(_ context.Context, m *metricdata.ResourceMetrics) error {
 				// The testSDKProducer produces testResourceMetricsA.
-				assert.Equal(t, testResourceMetricsAB, m)
+				assert.Equal(t, testResourceMetricsAB, *m)
 				*called = true
 				return assert.AnError
 			},