Start transient Accum

api/global/internal/meter.go

@@ -123,6 +123,9 @@ func (inst *instrument) Descriptor() metric.Descriptor {
 	return inst.descriptor
 }
 
+func (inst *instrument) Unref() {
+}
+
 // MeterProvider interface and delegation
 
 func newMeterProvider() *meterProvider {

api/metric/metrictest/meter.go

@@ -80,6 +80,9 @@ func (i Instrument) Descriptor() apimetric.Descriptor {
 	return i.descriptor
 }
 
+func (i Instrument) Unref() {
+}
+
 func (a *Async) Implementation() interface{} {
 	return a
 }

api/metric/noop.go

@@ -40,6 +40,9 @@ func (noopInstrument) Implementation() interface{} {
 	return nil
 }
 
+func (noopInstrument) Unref() {
+}
+
 func (noopInstrument) Descriptor() Descriptor {
 	return Descriptor{}
 }

api/metric/sdkapi.go

@@ -50,6 +50,9 @@ type InstrumentImpl interface {
 
 	// Descriptor returns a copy of the instrument's Descriptor.
 	Descriptor() Descriptor
+
+	// @@@
+	Unref()
 }
 
 // SyncImpl is the implementation-level interface to a generic

sdk/metric/sdk.go

@@ -154,6 +154,10 @@ func (inst *instrument) Descriptor() api.Descriptor {
 	return inst.descriptor
 }
 
+func (inst *instrument) Unref() {
+	// This is a no-op for the standard Accumulator.
+}
+
 func (a *asyncInstrument) Implementation() interface{} {
 	return a
 }

sdk/metric/transient/transient.go

@@ -0,0 +1,60 @@
+// 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 transient
+
+import (
+	"context"
+	"fmt"
+
+	"go.opentelemetry.io/otel/api/metric"
+	"go.opentelemetry.io/otel/label"
+	export "go.opentelemetry.io/otel/sdk/export/metric"
+	sdk "go.opentelemetry.io/otel/sdk/metric"
+)
+
+type Accumulator struct {
+	standard *sdk.Accumulator
+}
+
+var (
+	ErrAsyncNotSupported = fmt.Errorf("transient asynchronous instruments not supported")
+
+	_ metric.MeterImpl = &Accumulator{}
+)
+
+func NewAccumulator(processor export.Processor, opts ...sdk.Option) *Accumulator {
+	return &Accumulator{
+		standard: sdk.NewAccumulator(processor, opts...),
+	}
+}
+
+func (a *Accumulator) RecordBatch(ctx context.Context, labels []label.KeyValue, measurements ...metric.Measurement) {
+	a.standard.RecordBatch(ctx, labels, measurements...)
+}
+
+func (a *Accumulator) NewSyncInstrument(descriptor metric.Descriptor) (metric.SyncImpl, error) {
+	return a.standard.NewSyncInstrument(descriptor)
+}
+
+func (a *Accumulator) NewAsyncInstrument(
+	descriptor metric.Descriptor,
+	runner metric.AsyncRunner,
+) (metric.AsyncImpl, error) {
+	return metric.NoopAsync{}, ErrAsyncNotSupported
+}
+
+func (m *Accumulator) Collect(ctx context.Context) int {
+	return 0
+}