Move Aggregator interface to aggregator package (#2444)

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

exporters/otlp/otlpmetric/exporter_test.go

@@ -33,6 +33,7 @@ import (
 	"go.opentelemetry.io/otel/metric/number"
 	"go.opentelemetry.io/otel/metric/sdkapi"
 	"go.opentelemetry.io/otel/sdk/instrumentation"
+	"go.opentelemetry.io/otel/sdk/metric/aggregator"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator/histogram"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator/sum"
 	"go.opentelemetry.io/otel/sdk/metric/export"
@@ -682,7 +683,7 @@ func runMetricExportTests(t *testing.T, opts []otlpmetric.Option, res *resource.
 		desc := metrictest.NewDescriptor(r.name, r.iKind, r.nKind)
 		labs := attribute.NewSet(lcopy...)
 
-		var agg, ckpt export.Aggregator
+		var agg, ckpt aggregator.Aggregator
 		if r.iKind.Adding() {
 			sums := sum.New(2)
 			agg, ckpt = &sums[0], &sums[1]

exporters/otlp/otlpmetric/internal/metrictransform/metric_test.go

@@ -28,6 +28,7 @@ import (
 	"go.opentelemetry.io/otel/metric/metrictest"
 	"go.opentelemetry.io/otel/metric/number"
 	"go.opentelemetry.io/otel/metric/sdkapi"
+	"go.opentelemetry.io/otel/sdk/metric/aggregator"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator/lastvalue"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator/sum"
 	"go.opentelemetry.io/otel/sdk/metric/export"
@@ -241,10 +242,10 @@ func (t *testAgg) Aggregation() aggregation.Aggregation {
 func (t *testAgg) Update(ctx context.Context, number number.Number, descriptor *sdkapi.Descriptor) error {
 	return nil
 }
-func (t *testAgg) SynchronizedMove(destination export.Aggregator, descriptor *sdkapi.Descriptor) error {
+func (t *testAgg) SynchronizedMove(destination aggregator.Aggregator, descriptor *sdkapi.Descriptor) error {
 	return nil
 }
-func (t *testAgg) Merge(aggregator export.Aggregator, descriptor *sdkapi.Descriptor) error {
+func (t *testAgg) Merge(aggregator aggregator.Aggregator, descriptor *sdkapi.Descriptor) error {
 	return nil
 }
 
@@ -270,7 +271,7 @@ func (te *testErrSum) Kind() aggregation.Kind {
 	return aggregation.SumKind
 }
 
-var _ export.Aggregator = &testAgg{}
+var _ aggregator.Aggregator = &testAgg{}
 var _ aggregation.Aggregation = &testAgg{}
 var _ aggregation.Sum = &testErrSum{}
 var _ aggregation.LastValue = &testErrLastValue{}

sdk/export/metric/metric.go

@@ -19,15 +19,16 @@ import (
 
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/metric/sdkapi"
+	"go.opentelemetry.io/otel/sdk/metric/aggregator"
 	"go.opentelemetry.io/otel/sdk/metric/export"
 	"go.opentelemetry.io/otel/sdk/metric/export/aggregation"
 )
 
 // Deprecated: use module "go.opentelemetry.io/otel/sdk/metric/export"
 type Accumulation = export.Accumulation
 
-// Deprecated: use module "go.opentelemetry.io/otel/sdk/metric/export"
-type Aggregator = export.Aggregator
+// Deprecated: use module "go.opentelemetry.io/otel/sdk/metric/aggregator"
+type Aggregator = aggregator.Aggregator
 
 // Deprecated: use module "go.opentelemetry.io/otel/sdk/metric/export"
 type AggregatorSelector = export.AggregatorSelector

sdk/metric/aggregator/aggregator.go

@@ -15,19 +15,81 @@
 package aggregator // import "go.opentelemetry.io/otel/sdk/metric/aggregator"
 
 import (
+	"context"
 	"fmt"
 	"math"
 
 	"go.opentelemetry.io/otel/metric/number"
 	"go.opentelemetry.io/otel/metric/sdkapi"
-	"go.opentelemetry.io/otel/sdk/metric/export"
 	"go.opentelemetry.io/otel/sdk/metric/export/aggregation"
 )
 
+// Aggregator implements a specific aggregation behavior, e.g., a
+// behavior to track a sequence of updates to an instrument.  Counter
+// instruments commonly use a simple Sum aggregator, but for the
+// distribution instruments (Histogram, GaugeObserver) there are a
+// number of possible aggregators with different cost and accuracy
+// tradeoffs.
+//
+// Note that any Aggregator may be attached to any instrument--this is
+// the result of the OpenTelemetry API/SDK separation.  It is possible
+// to attach a Sum aggregator to a Histogram instrument.
+type Aggregator interface {
+	// Aggregation returns an Aggregation interface to access the
+	// current state of this Aggregator.  The caller is
+	// responsible for synchronization and must not call any the
+	// other methods in this interface concurrently while using
+	// the Aggregation.
+	Aggregation() aggregation.Aggregation
+
+	// Update receives a new measured value and incorporates it
+	// into the aggregation.  Update() calls may be called
+	// concurrently.
+	//
+	// Descriptor.NumberKind() should be consulted to determine
+	// whether the provided number is an int64 or float64.
+	//
+	// The Context argument comes from user-level code and could be
+	// inspected for a `correlation.Map` or `trace.SpanContext`.
+	Update(ctx context.Context, number number.Number, descriptor *sdkapi.Descriptor) error
+
+	// SynchronizedMove is called during collection to finish one
+	// period of aggregation by atomically saving the
+	// currently-updating state into the argument Aggregator AND
+	// resetting the current value to the zero state.
+	//
+	// SynchronizedMove() is called concurrently with Update().  These
+	// two methods must be synchronized with respect to each
+	// other, for correctness.
+	//
+	// After saving a synchronized copy, the Aggregator can be converted
+	// into one or more of the interfaces in the `aggregation` sub-package,
+	// according to kind of Aggregator that was selected.
+	//
+	// This method will return an InconsistentAggregatorError if
+	// this Aggregator cannot be copied into the destination due
+	// to an incompatible type.
+	//
+	// This call has no Context argument because it is expected to
+	// perform only computation.
+	//
+	// When called with a nil `destination`, this Aggregator is reset
+	// and the current value is discarded.
+	SynchronizedMove(destination Aggregator, descriptor *sdkapi.Descriptor) error
+
+	// Merge combines the checkpointed state from the argument
+	// Aggregator into this Aggregator.  Merge is not synchronized
+	// with respect to Update or SynchronizedMove.
+	//
+	// The owner of an Aggregator being merged is responsible for
+	// synchronization of both Aggregator states.
+	Merge(aggregator Aggregator, descriptor *sdkapi.Descriptor) error
+}
+
 // NewInconsistentAggregatorError formats an error describing an attempt to
 // Checkpoint or Merge different-type aggregators.  The result can be unwrapped as
 // an ErrInconsistentType.
-func NewInconsistentAggregatorError(a1, a2 export.Aggregator) error {
+func NewInconsistentAggregatorError(a1, a2 Aggregator) error {
 	return fmt.Errorf("%w: %T and %T", aggregation.ErrInconsistentType, a1, a2)
 }
 

sdk/metric/aggregator/aggregatortest/test.go

@@ -30,7 +30,6 @@ import (
 	"go.opentelemetry.io/otel/metric/number"
 	"go.opentelemetry.io/otel/metric/sdkapi"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator"
-	"go.opentelemetry.io/otel/sdk/metric/export"
 	"go.opentelemetry.io/otel/sdk/metric/export/aggregation"
 )
 
@@ -44,7 +43,7 @@ type Profile struct {
 type NoopAggregator struct{}
 type NoopAggregation struct{}
 
-var _ export.Aggregator = NoopAggregator{}
+var _ aggregator.Aggregator = NoopAggregator{}
 var _ aggregation.Aggregation = NoopAggregation{}
 
 func newProfiles() []Profile {
@@ -150,7 +149,7 @@ func (n *Numbers) Points() []number.Number {
 }
 
 // CheckedUpdate performs the same range test the SDK does on behalf of the aggregator.
-func CheckedUpdate(t *testing.T, agg export.Aggregator, number number.Number, descriptor *sdkapi.Descriptor) {
+func CheckedUpdate(t *testing.T, agg aggregator.Aggregator, number number.Number, descriptor *sdkapi.Descriptor) {
 	ctx := context.Background()
 
 	// Note: Aggregator tests are written assuming that the SDK
@@ -166,7 +165,7 @@ func CheckedUpdate(t *testing.T, agg export.Aggregator, number number.Number, de
 	}
 }
 
-func CheckedMerge(t *testing.T, aggInto, aggFrom export.Aggregator, descriptor *sdkapi.Descriptor) {
+func CheckedMerge(t *testing.T, aggInto, aggFrom aggregator.Aggregator, descriptor *sdkapi.Descriptor) {
 	if err := aggInto.Merge(aggFrom, descriptor); err != nil {
 		t.Error("Unexpected Merge failure", err)
 	}
@@ -184,15 +183,15 @@ func (NoopAggregator) Update(context.Context, number.Number, *sdkapi.Descriptor)
 	return nil
 }
 
-func (NoopAggregator) SynchronizedMove(export.Aggregator, *sdkapi.Descriptor) error {
+func (NoopAggregator) SynchronizedMove(aggregator.Aggregator, *sdkapi.Descriptor) error {
 	return nil
 }
 
-func (NoopAggregator) Merge(export.Aggregator, *sdkapi.Descriptor) error {
+func (NoopAggregator) Merge(aggregator.Aggregator, *sdkapi.Descriptor) error {
 	return nil
 }
 
-func SynchronizedMoveResetTest(t *testing.T, mkind sdkapi.InstrumentKind, nf func(*sdkapi.Descriptor) export.Aggregator) {
+func SynchronizedMoveResetTest(t *testing.T, mkind sdkapi.InstrumentKind, nf func(*sdkapi.Descriptor) aggregator.Aggregator) {
 	t.Run("reset on nil", func(t *testing.T) {
 		// Ensures that SynchronizedMove(nil, descriptor) discards and
 		// resets the aggregator.

sdk/metric/aggregator/histogram/histogram.go

@@ -22,7 +22,6 @@ import (
 	"go.opentelemetry.io/otel/metric/number"
 	"go.opentelemetry.io/otel/metric/sdkapi"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator"
-	"go.opentelemetry.io/otel/sdk/metric/export"
 	"go.opentelemetry.io/otel/sdk/metric/export/aggregation"
 )
 
@@ -97,7 +96,7 @@ var defaultInt64ExplicitBoundaries = func(bounds []float64) (asint []float64) {
 	return
 }(defaultFloat64ExplicitBoundaries)
 
-var _ export.Aggregator = &Aggregator{}
+var _ aggregator.Aggregator = &Aggregator{}
 var _ aggregation.Sum = &Aggregator{}
 var _ aggregation.Count = &Aggregator{}
 var _ aggregation.Histogram = &Aggregator{}
@@ -174,7 +173,7 @@ func (c *Aggregator) Histogram() (aggregation.Buckets, error) {
 // the empty set.  Since no locks are taken, there is a chance that
 // the independent Sum, Count and Bucket Count are not consistent with each
 // other.
-func (c *Aggregator) SynchronizedMove(oa export.Aggregator, desc *sdkapi.Descriptor) error {
+func (c *Aggregator) SynchronizedMove(oa aggregator.Aggregator, desc *sdkapi.Descriptor) error {
 	o, _ := oa.(*Aggregator)
 
 	if oa != nil && o == nil {
@@ -254,7 +253,7 @@ func (c *Aggregator) Update(_ context.Context, number number.Number, desc *sdkap
 }
 
 // Merge combines two histograms that have the same buckets into a single one.
-func (c *Aggregator) Merge(oa export.Aggregator, desc *sdkapi.Descriptor) error {
+func (c *Aggregator) Merge(oa aggregator.Aggregator, desc *sdkapi.Descriptor) error {
 	o, _ := oa.(*Aggregator)
 	if o == nil {
 		return aggregator.NewInconsistentAggregatorError(c, oa)

sdk/metric/aggregator/histogram/histogram_test.go

@@ -25,9 +25,9 @@ import (
 
 	"go.opentelemetry.io/otel/metric/number"
 	"go.opentelemetry.io/otel/metric/sdkapi"
+	"go.opentelemetry.io/otel/sdk/metric/aggregator"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator/aggregatortest"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator/histogram"
-	"go.opentelemetry.io/otel/sdk/metric/export"
 )
 
 const count = 100
@@ -240,7 +240,7 @@ func TestSynchronizedMoveReset(t *testing.T) {
 	aggregatortest.SynchronizedMoveResetTest(
 		t,
 		sdkapi.HistogramInstrumentKind,
-		func(desc *sdkapi.Descriptor) export.Aggregator {
+		func(desc *sdkapi.Descriptor) aggregator.Aggregator {
 			return &histogram.New(1, desc, histogram.WithExplicitBoundaries(testBoundaries))[0]
 		},
 	)

sdk/metric/aggregator/lastvalue/lastvalue.go

@@ -23,7 +23,6 @@ import (
 	"go.opentelemetry.io/otel/metric/number"
 	"go.opentelemetry.io/otel/metric/sdkapi"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator"
-	"go.opentelemetry.io/otel/sdk/metric/export"
 	"go.opentelemetry.io/otel/sdk/metric/export/aggregation"
 )
 
@@ -51,7 +50,7 @@ type (
 	}
 )
 
-var _ export.Aggregator = &Aggregator{}
+var _ aggregator.Aggregator = &Aggregator{}
 var _ aggregation.LastValue = &Aggregator{}
 
 // An unset lastValue has zero timestamp and zero value.
@@ -92,7 +91,7 @@ func (g *Aggregator) LastValue() (number.Number, time.Time, error) {
 }
 
 // SynchronizedMove atomically saves the current value.
-func (g *Aggregator) SynchronizedMove(oa export.Aggregator, _ *sdkapi.Descriptor) error {
+func (g *Aggregator) SynchronizedMove(oa aggregator.Aggregator, _ *sdkapi.Descriptor) error {
 	if oa == nil {
 		atomic.StorePointer(&g.value, unsafe.Pointer(unsetLastValue))
 		return nil
@@ -117,7 +116,7 @@ func (g *Aggregator) Update(_ context.Context, number number.Number, desc *sdkap
 
 // Merge combines state from two aggregators.  The most-recently set
 // value is chosen.
-func (g *Aggregator) Merge(oa export.Aggregator, desc *sdkapi.Descriptor) error {
+func (g *Aggregator) Merge(oa aggregator.Aggregator, desc *sdkapi.Descriptor) error {
 	o, _ := oa.(*Aggregator)
 	if o == nil {
 		return aggregator.NewInconsistentAggregatorError(g, oa)

sdk/metric/aggregator/lastvalue/lastvalue_test.go

@@ -27,14 +27,14 @@ import (
 	ottest "go.opentelemetry.io/otel/internal/internaltest"
 	"go.opentelemetry.io/otel/metric/number"
 	"go.opentelemetry.io/otel/metric/sdkapi"
+	"go.opentelemetry.io/otel/sdk/metric/aggregator"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator/aggregatortest"
-	"go.opentelemetry.io/otel/sdk/metric/export"
 	"go.opentelemetry.io/otel/sdk/metric/export/aggregation"
 )
 
 const count = 100
 
-var _ export.Aggregator = &Aggregator{}
+var _ aggregator.Aggregator = &Aggregator{}
 
 // Ensure struct alignment prior to running tests.
 func TestMain(m *testing.M) {
@@ -139,7 +139,7 @@ func TestSynchronizedMoveReset(t *testing.T) {
 	aggregatortest.SynchronizedMoveResetTest(
 		t,
 		sdkapi.GaugeObserverInstrumentKind,
-		func(desc *sdkapi.Descriptor) export.Aggregator {
+		func(desc *sdkapi.Descriptor) aggregator.Aggregator {
 			return &New(1)[0]
 		},
 	)

sdk/metric/aggregator/sum/sum.go

@@ -20,7 +20,6 @@ import (
 	"go.opentelemetry.io/otel/metric/number"
 	"go.opentelemetry.io/otel/metric/sdkapi"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator"
-	"go.opentelemetry.io/otel/sdk/metric/export"
 	"go.opentelemetry.io/otel/sdk/metric/export/aggregation"
 )
 
@@ -31,7 +30,7 @@ type Aggregator struct {
 	value number.Number
 }
 
-var _ export.Aggregator = &Aggregator{}
+var _ aggregator.Aggregator = &Aggregator{}
 var _ aggregation.Sum = &Aggregator{}
 
 // New returns a new counter aggregator implemented by atomic
@@ -59,7 +58,7 @@ func (c *Aggregator) Sum() (number.Number, error) {
 
 // SynchronizedMove atomically saves the current value into oa and resets the
 // current sum to zero.
-func (c *Aggregator) SynchronizedMove(oa export.Aggregator, _ *sdkapi.Descriptor) error {
+func (c *Aggregator) SynchronizedMove(oa aggregator.Aggregator, _ *sdkapi.Descriptor) error {
 	if oa == nil {
 		c.value.SetRawAtomic(0)
 		return nil
@@ -79,7 +78,7 @@ func (c *Aggregator) Update(_ context.Context, num number.Number, desc *sdkapi.D
 }
 
 // Merge combines two counters by adding their sums.
-func (c *Aggregator) Merge(oa export.Aggregator, desc *sdkapi.Descriptor) error {
+func (c *Aggregator) Merge(oa aggregator.Aggregator, desc *sdkapi.Descriptor) error {
 	o, _ := oa.(*Aggregator)
 	if o == nil {
 		return aggregator.NewInconsistentAggregatorError(c, oa)

sdk/metric/aggregator/sum/sum_test.go

@@ -24,8 +24,8 @@ import (
 	ottest "go.opentelemetry.io/otel/internal/internaltest"
 	"go.opentelemetry.io/otel/metric/number"
 	"go.opentelemetry.io/otel/metric/sdkapi"
+	"go.opentelemetry.io/otel/sdk/metric/aggregator"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator/aggregatortest"
-	"go.opentelemetry.io/otel/sdk/metric/export"
 )
 
 const count = 100
@@ -147,7 +147,7 @@ func TestSynchronizedMoveReset(t *testing.T) {
 	aggregatortest.SynchronizedMoveResetTest(
 		t,
 		sdkapi.CounterObserverInstrumentKind,
-		func(desc *sdkapi.Descriptor) export.Aggregator {
+		func(desc *sdkapi.Descriptor) aggregator.Aggregator {
 			return &New(1)[0]
 		},
 	)

sdk/metric/correct_test.go

@@ -28,6 +28,7 @@ import (
 	"go.opentelemetry.io/otel/metric"
 	"go.opentelemetry.io/otel/metric/sdkapi"
 	metricsdk "go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/aggregator"
 	"go.opentelemetry.io/otel/sdk/metric/export"
 	"go.opentelemetry.io/otel/sdk/metric/export/aggregation"
 	"go.opentelemetry.io/otel/sdk/metric/processor/processortest"
@@ -72,7 +73,7 @@ type testSelector struct {
 	newAggCount int
 }
 
-func (ts *testSelector) AggregatorFor(desc *sdkapi.Descriptor, aggPtrs ...*export.Aggregator) {
+func (ts *testSelector) AggregatorFor(desc *sdkapi.Descriptor, aggPtrs ...*aggregator.Aggregator) {
 	ts.newAggCount += len(aggPtrs)
 	processortest.AggregatorSelector().AggregatorFor(desc, aggPtrs...)
 }