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>

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())
 	)