metrics/exporter: define MetricsExporter interface. (#219)

exporter/metrics_exporter.go

@@ -0,0 +1,44 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package exporter
+
+import (
+	"context"
+
+	"github.com/census-instrumentation/opencensus-service/data"
+)
+
+// MetricsExporter is an interface that receives data.MetricsData, converts it as needed, and
+// sends it to different destinations.
+//
+// ExportMetricsData receives data.MetricsData for processing by the exporter.
+type MetricsExporter interface {
+	ExportMetricsData(ctx context.Context, md data.MetricsData) error
+}
+
+// MultiMetricsExporters wraps multiple metrics exporters in a single one.
+func MultiMetricsExporters(mes ...MetricsExporter) MetricsExporter {
+	return metricsExporters(mes)
+}
+
+type metricsExporters []MetricsExporter
+
+// ExportMetricsData exports the MetricsData to all exporters wrapped by the current one.
+func (mes metricsExporters) ExportMetricsData(ctx context.Context, md data.MetricsData) error {
+	for _, me := range mes {
+		_ = me.ExportMetricsData(ctx, md)
+	}
+	return nil
+}