OTLP metrics gRPC exporter

.github/dependabot.yml

@@ -266,3 +266,23 @@ updates:
     schedule:
       day: sunday
       interval: weekly
+  -
+    package-ecosystem: gomod
+    directory: /exporters/otlp/otlpmetric
+    labels:
+      - dependencies
+      - go
+      - "Skip Changelog"
+    schedule:
+      day: sunday
+      interval: weekly
+  -
+    package-ecosystem: gomod
+    directory: /exporters/otlp/otlpmetric/otlpmetricgrpc
+    labels:
+      - dependencies
+      - go
+      - "Skip Changelog"
+    schedule:
+      day: sunday
+      interval: weekly

CHANGELOG.md

@@ -40,6 +40,8 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Creates package `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp` implementing a HTTP `otlptrace.Client` and offers convenience functions, `NewExportPipeline` and `InstallNewPipeline`, to setup and install a `otlptrace.Exporter` in tracing. (#1963)
 - Changes `go.opentelemetry.io/otel/sdk/resource.NewWithAttributes` to require a schema URL. The old function is still available as `resource.NewSchemaless`. This is a breaking change. (#1938)
 - Several builtin resource detectors now correctly populate the schema URL. (#1938)
+- Creates package `go.opentelemetry.io/otel/exporters/otlp/otlpmetric` that defines a metrics exporter that uses a `otlpmetric.Client` to send data.
+  Creates package `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc` implementing a gRPC `otlpmetric.Client` and offers convenience functions, `New` and `NewUnstarted`, to create an `otlpmetric.Exporter`.(#1991)
 
 ### Changed
 

bridge/opencensus/go.mod

@@ -63,3 +63,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../..
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp => ../../exporters/otlp/otlptrace/otlptracehttp
 
 replace go.opentelemetry.io/otel/internal/metric => ../../internal/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric => ../../exporters/otlp/otlpmetric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../exporters/otlp/otlpmetric/otlpmetricgrpc

bridge/opentracing/go.mod

@@ -59,3 +59,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../..
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp => ../../exporters/otlp/otlptrace/otlptracehttp
 
 replace go.opentelemetry.io/otel/internal/metric => ../../internal/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric => ../../exporters/otlp/otlpmetric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../exporters/otlp/otlpmetric/otlpmetricgrpc

example/jaeger/go.mod

@@ -59,3 +59,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../..
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp => ../../exporters/otlp/otlptrace/otlptracehttp
 
 replace go.opentelemetry.io/otel/internal/metric => ../../internal/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric => ../../exporters/otlp/otlpmetric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../exporters/otlp/otlpmetric/otlpmetricgrpc

example/namedtracer/go.mod

@@ -60,3 +60,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../..
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp => ../../exporters/otlp/otlptrace/otlptracehttp
 
 replace go.opentelemetry.io/otel/internal/metric => ../../internal/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric => ../../exporters/otlp/otlpmetric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../exporters/otlp/otlpmetric/otlpmetricgrpc

example/opencensus/go.mod

@@ -61,3 +61,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../..
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp => ../../exporters/otlp/otlptrace/otlptracehttp
 
 replace go.opentelemetry.io/otel/internal/metric => ../../internal/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric => ../../exporters/otlp/otlpmetric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../exporters/otlp/otlpmetric/otlpmetricgrpc

example/otel-collector/go.mod

@@ -62,3 +62,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../..
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp => ../../exporters/otlp/otlptrace/otlptracehttp
 
 replace go.opentelemetry.io/otel/internal/metric => ../../internal/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric => ../../exporters/otlp/otlpmetric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../exporters/otlp/otlpmetric/otlpmetricgrpc

example/passthrough/go.mod

@@ -61,3 +61,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../..
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp => ../../exporters/otlp/otlptrace/otlptracehttp
 
 replace go.opentelemetry.io/otel/internal/metric => ../../internal/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric => ../../exporters/otlp/otlpmetric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../exporters/otlp/otlpmetric/otlpmetricgrpc

example/prometheus/go.mod

@@ -61,3 +61,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../..
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp => ../../exporters/otlp/otlptrace/otlptracehttp
 
 replace go.opentelemetry.io/otel/internal/metric => ../../internal/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric => ../../exporters/otlp/otlpmetric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../exporters/otlp/otlpmetric/otlpmetricgrpc

example/zipkin/go.mod

@@ -60,3 +60,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../..
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp => ../../exporters/otlp/otlptrace/otlptracehttp
 
 replace go.opentelemetry.io/otel/internal/metric => ../../internal/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric => ../../exporters/otlp/otlpmetric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../exporters/otlp/otlpmetric/otlpmetricgrpc

exporters/metric/prometheus/go.mod

@@ -64,3 +64,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../..
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp => ../../otlp/otlptrace/otlptracehttp
 
 replace go.opentelemetry.io/otel/internal/metric => ../../../internal/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric => ../../otlp/otlpmetric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../otlp/otlpmetric/otlpmetricgrpc

exporters/otlp/otlpmetric/clients.go

@@ -0,0 +1,43 @@
+// Copyright The OpenTelemetry 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 otlpmetric // import "go.opentelemetry.io/otel/exporters/otlp/otlpmetric"
+
+import (
+	"context"
+
+	metricpb "go.opentelemetry.io/proto/otlp/metrics/v1"
+)
+
+// Client manages connections to the collector, handles the
+// transformation of data into wire format, and the transmission of that
+// data to the collector.
+type Client interface {
+	// Start should establish connection(s) to endpoint(s). It is
+	// called just once by the exporter, so the implementation
+	// does not need to worry about idempotence and locking.
+	Start(ctx context.Context) error
+	// Stop should close the connections. The function is called
+	// only once by the exporter, so the implementation does not
+	// need to worry about idempotence, but it may be called
+	// concurrently with UploadMetrics, so proper
+	// locking is required. The function serves as a
+	// synchronization point - after the function returns, the
+	// process of closing connections is assumed to be finished.
+	Stop(ctx context.Context) error
+	// UploadMetrics should transform the passed metrics to the
+	// wire format and send it to the collector. May be called
+	// concurrently.
+	UploadMetrics(ctx context.Context, protoMetrics []*metricpb.ResourceMetrics) error
+}

exporters/otlp/otlpmetric/exporter.go

@@ -0,0 +1,127 @@
+// Copyright The OpenTelemetry 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 otlpmetric
+
+import (
+	"context"
+	"errors"
+	"sync"
+
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/internal/metrictransform"
+	"go.opentelemetry.io/otel/metric"
+	metricsdk "go.opentelemetry.io/otel/sdk/export/metric"
+	"go.opentelemetry.io/otel/sdk/export/metric/aggregation"
+)
+
+var (
+	errAlreadyStarted = errors.New("already started")
+)
+
+// Exporter exports metrics data in the OTLP wire format.
+type Exporter struct {
+	client             Client
+	exportKindSelector metricsdk.ExportKindSelector
+
+	mu      sync.RWMutex
+	started bool
+
+	startOnce sync.Once
+	stopOnce  sync.Once
+}
+
+// Export exports a batch of metrics.
+func (e *Exporter) Export(ctx context.Context, checkpointSet metricsdk.CheckpointSet) error {
+	rms, err := metrictransform.CheckpointSet(ctx, e, checkpointSet, 1)
+	if err != nil {
+		return err
+	}
+	if len(rms) == 0 {
+		return nil
+	}
+
+	return e.client.UploadMetrics(ctx, rms)
+}
+
+// Start establishes a connection to the receiving endpoint.
+func (e *Exporter) Start(ctx context.Context) error {
+	var err = errAlreadyStarted
+	e.startOnce.Do(func() {
+		e.mu.Lock()
+		e.started = true
+		e.mu.Unlock()
+		err = e.client.Start(ctx)
+	})
+
+	return err
+}
+
+// Shutdown flushes all exports and closes all connections to the receiving endpoint.
+func (e *Exporter) Shutdown(ctx context.Context) error {
+
+	e.mu.RLock()
+	started := e.started
+	e.mu.RUnlock()
+
+	if !started {
+		return nil
+	}
+
+	var err error
+
+	e.stopOnce.Do(func() {
+		err = e.client.Stop(ctx)
+		e.mu.Lock()
+		e.started = false
+		e.mu.Unlock()
+	})
+
+	return err
+}
+
+func (e *Exporter) ExportKindFor(descriptor *metric.Descriptor, aggregatorKind aggregation.Kind) metricsdk.ExportKind {
+	return e.exportKindSelector.ExportKindFor(descriptor, aggregatorKind)
+}
+
+var _ metricsdk.Exporter = (*Exporter)(nil)
+
+// New constructs a new Exporter and starts it.
+func New(ctx context.Context, client Client, opts ...Option) (*Exporter, error) {
+	exp := NewUnstarted(client, opts...)
+	if err := exp.Start(ctx); err != nil {
+		return nil, err
+	}
+	return exp, nil
+}
+
+// NewUnstarted constructs a new Exporter and does not start it.
+func NewUnstarted(client Client, opts ...Option) *Exporter {
+	cfg := config{
+		// Note: the default ExportKindSelector is specified
+		// as Cumulative:
+		// https://github.com/open-telemetry/opentelemetry-specification/issues/731
+		exportKindSelector: metricsdk.CumulativeExportKindSelector(),
+	}
+
+	for _, opt := range opts {
+		opt.apply(&cfg)
+	}
+
+	e := &Exporter{
+		client:             client,
+		exportKindSelector: cfg.exportKindSelector,
+	}
+
+	return e
+}