Adds a filter Aggregator.

sdk/metric/internal/filter.go

@@ -0,0 +1,68 @@
+// 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.
+
+//go:build go1.18
+// +build go1.18
+
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
+
+import (
+	"sync"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+)
+
+// filter is an aggregator that applies attribute filter when Aggregating. filters
+// do not have any backing memory, and must be constructed with a backing Aggregator.
+type filter[N int64 | float64] struct {
+	filter     func(attribute.Set) attribute.Set
+	aggregator Aggregator[N]
+
+	sync.Mutex
+	seen map[attribute.Set]attribute.Set
+}
+
+// NewFilter wraps an Aggregator with an attribute filtering function.
+func NewFilter[N int64 | float64](agg Aggregator[N], fn func(attribute.Set) attribute.Set) Aggregator[N] {
+	if fn == nil {
+		return agg
+	}
+	return &filter[N]{
+		filter:     fn,
+		aggregator: agg,
+		seen:       map[attribute.Set]attribute.Set{},
+	}
+}
+
+// Aggregate records the measurement, scoped by attr, and aggregates it
+// into an aggregation.
+
+// TODO (#3006): drop stale attributes from seen.
+func (f *filter[N]) Aggregate(measurement N, attr attribute.Set) {
+	f.Lock()
+	defer f.Unlock()
+	fAttr, ok := f.seen[attr]
+	if !ok {
+		fAttr = f.filter(attr)
+		f.seen[attr] = fAttr
+	}
+	f.aggregator.Aggregate(measurement, fAttr)
+}
+
+// Aggregation returns an Aggregation, for all the aggregated
+// measurements made and ends an aggregation cycle.
+func (f *filter[N]) Aggregation() metricdata.Aggregation {
+	return f.aggregator.Aggregation()
+}

sdk/metric/internal/filter_test.go

@@ -0,0 +1,202 @@
+// 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.
+
+//go:build go1.18
+// +build go1.18
+
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
+
+import (
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+)
+
+// This is an aggregator that has a stable output, used for testing. It does not
+// follow any spec prescribed aggregation.
+type testStableAggregator[N int64 | float64] struct {
+	sync.Mutex
+	values []metricdata.DataPoint[N]
+}
+
+// Aggregate records the measurement, scoped by attr, and aggregates it
+// into an aggregation.
+func (a *testStableAggregator[N]) Aggregate(measurement N, attr attribute.Set) {
+	a.Lock()
+	defer a.Unlock()
+
+	a.values = append(a.values, metricdata.DataPoint[N]{
+		Attributes: attr,
+		Value:      measurement,
+	})
+}
+
+// Aggregation returns an Aggregation, for all the aggregated
+// measurements made and ends an aggregation cycle.
+func (a *testStableAggregator[N]) Aggregation() metricdata.Aggregation {
+	return metricdata.Gauge[N]{
+		DataPoints: a.values,
+	}
+}
+
+func testNewFilterNoFilter[N int64 | float64](t *testing.T, agg Aggregator[N]) {
+	filter := NewFilter(agg, nil)
+	assert.Equal(t, agg, filter)
+}
+
+func testNewFilter[N int64 | float64](t *testing.T, agg Aggregator[N]) {
+	f := NewFilter(agg, testAttributeFilter)
+	require.IsType(t, &filter[N]{}, f)
+	filt := f.(*filter[N])
+	assert.Equal(t, agg, filt.aggregator)
+}
+
+func testAttributeFilter(input attribute.Set) attribute.Set {
+	out, _ := input.Filter(func(kv attribute.KeyValue) bool {
+		return kv.Key == "power-level"
+	})
+	return out
+}
+
+func TestNewFilter(t *testing.T) {
+	t.Run("int64", func(t *testing.T) {
+		agg := &testStableAggregator[int64]{}
+		testNewFilterNoFilter[int64](t, agg)
+		testNewFilter[int64](t, agg)
+	})
+	t.Run("float64", func(t *testing.T) {
+		agg := &testStableAggregator[float64]{}
+		testNewFilterNoFilter[float64](t, agg)
+		testNewFilter[float64](t, agg)
+	})
+}
+
+func testDataPoint[N int64 | float64](attr attribute.Set) metricdata.DataPoint[N] {
+	return metricdata.DataPoint[N]{
+		Attributes: attr,
+		Value:      1,
+	}
+}
+
+func testFilterAggregate[N int64 | float64](t *testing.T) {
+	testCases := []struct {
+		name      string
+		inputAttr []attribute.Set
+		output    []metricdata.DataPoint[N]
+	}{
+		{
+			name: "Will filter all out",
+			inputAttr: []attribute.Set{
+				attribute.NewSet(
+					attribute.String("foo", "bar"),
+					attribute.Float64("lifeUniverseEverything", 42.0),
+				),
+			},
+			output: []metricdata.DataPoint[N]{
+				testDataPoint[N](*attribute.EmptySet()),
+			},
+		},
+		{
+			name: "Will keep appropriate attributes",
+			inputAttr: []attribute.Set{
+				attribute.NewSet(
+					attribute.String("foo", "bar"),
+					attribute.Int("power-level", 9001),
+					attribute.Float64("lifeUniverseEverything", 42.0),
+				),
+				attribute.NewSet(
+					attribute.String("foo", "bar"),
+					attribute.Int("power-level", 9001),
+				),
+			},
+			output: []metricdata.DataPoint[N]{
+				// A real Aggregator will combine these, the testAggregator doesn't for list stability.
+				testDataPoint[N](attribute.NewSet(attribute.Int("power-level", 9001))),
+				testDataPoint[N](attribute.NewSet(attribute.Int("power-level", 9001))),
+			},
+		},
+		{
+			name: "Will combine Aggregations",
+			inputAttr: []attribute.Set{
+				attribute.NewSet(
+					attribute.String("foo", "bar"),
+				),
+				attribute.NewSet(
+					attribute.Float64("lifeUniverseEverything", 42.0),
+				),
+			},
+			output: []metricdata.DataPoint[N]{
+				// A real Aggregator will combine these, the testAggregator doesn't for list stability.
+				testDataPoint[N](*attribute.EmptySet()),
+				testDataPoint[N](*attribute.EmptySet()),
+			},
+		},
+	}
+
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			f := NewFilter[N](&testStableAggregator[N]{}, testAttributeFilter)
+			for _, set := range tt.inputAttr {
+				f.Aggregate(1, set)
+			}
+			out := f.Aggregation().(metricdata.Gauge[N])
+			assert.Equal(t, tt.output, out.DataPoints)
+		})
+	}
+}
+
+func TestFilterAggregate(t *testing.T) {
+	t.Run("int64", func(t *testing.T) {
+		testFilterAggregate[int64](t)
+	})
+	t.Run("float64", func(t *testing.T) {
+		testFilterAggregate[float64](t)
+	})
+}
+
+func testFilterConcurrent[N int64 | float64](t *testing.T) {
+	f := NewFilter[N](&testStableAggregator[N]{}, testAttributeFilter)
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	go func() {
+		f.Aggregate(1, attribute.NewSet(
+			attribute.String("foo", "bar"),
+		))
+		wg.Done()
+	}()
+
+	go func() {
+		f.Aggregate(1, attribute.NewSet(
+			attribute.Int("power-level", 9001),
+		))
+		wg.Done()
+	}()
+
+	wg.Wait()
+}
+
+func TestFilterConcurrent(t *testing.T) {
+	t.Run("int64", func(t *testing.T) {
+		testFilterConcurrent[int64](t)
+	})
+	t.Run("float64", func(t *testing.T) {
+		testFilterConcurrent[float64](t)
+	})
+}