Change ExportMetric api to ExportMetricProto (#106)

* Change ExportMetric api to ExportMetricProto

* restrict to name change.

* accept slice of metric
Change the api to ExportMetricsProto to reflect that it accepts more
than one metric.

* fix review comment.

equivalence_test.go

@@ -275,9 +275,7 @@ func TestEquivalenceStatsVsMetricsUploads(t *testing.T) {
 	oce.Flush()
 
 	ma.forEachRequest(func(emr *agentmetricspb.ExportMetricsServiceRequest) {
-		for _, metric := range emr.Metrics {
-			_ = se.ExportMetric(context.Background(), emr.Node, emr.Resource, metric)
-		}
+		_ = se.ExportMetricsProto(context.Background(), emr.Node, emr.Resource, emr.Metrics)
 	})
 	se.Flush()
 

metrics.go

@@ -49,18 +49,20 @@ type metricPayload struct {
 	metric   *metricspb.Metric
 }
 
-// ExportMetric exports OpenCensus Metrics to Stackdriver Monitoring.
-func (se *statsExporter) ExportMetric(ctx context.Context, node *commonpb.Node, rsc *resourcepb.Resource, metric *metricspb.Metric) error {
-	if metric == nil {
+// ExportMetricsProto exports OpenCensus Metrics Proto to Stackdriver Monitoring.
+func (se *statsExporter) ExportMetricsProto(ctx context.Context, node *commonpb.Node, rsc *resourcepb.Resource, metrics []*metricspb.Metric) error {
+	if len(metrics) == 0 {
 		return errNilMetric
 	}
 
-	payload := &metricPayload{
-		metric:   metric,
-		resource: rsc,
-		node:     node,
+	for _, metric := range metrics {
+		payload := &metricPayload{
+			metric:   metric,
+			resource: rsc,
+			node:     node,
+		}
+		se.protoMetricsBundler.Add(payload, 1)
 	}
-	se.protoMetricsBundler.Add(payload, 1)
 
 	return nil
 }

stackdriver.go

@@ -345,9 +345,9 @@ func (e *Exporter) ExportView(vd *view.Data) {
 	e.statsExporter.ExportView(vd)
 }
 
-// ExportMetric exports OpenCensus Metrics to Stackdriver Monitoring.
-func (e *Exporter) ExportMetric(ctx context.Context, node *commonpb.Node, rsc *resourcepb.Resource, metric *metricspb.Metric) error {
-	return e.statsExporter.ExportMetric(ctx, node, rsc, metric)
+// ExportMetricsProto exports OpenCensus Metrics Proto to Stackdriver Monitoring.
+func (e *Exporter) ExportMetricsProto(ctx context.Context, node *commonpb.Node, rsc *resourcepb.Resource, metrics []*metricspb.Metric) error {
+	return e.statsExporter.ExportMetricsProto(ctx, node, rsc, metrics)
 }
 
 // ExportSpan exports a SpanData to Stackdriver Trace.