Encapsulate SDK Tracer observability

sdk/trace/internal/observ/tracer.go

@@ -0,0 +1,223 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package observ // import "go.opentelemetry.io/otel/sdk/trace/internal/observ"
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/sdk"
+	"go.opentelemetry.io/otel/sdk/trace/internal/x"
+	"go.opentelemetry.io/otel/semconv/v1.37.0/otelconv"
+	"go.opentelemetry.io/otel/trace"
+)
+
+var meterOpts = []metric.MeterOption{
+	metric.WithInstrumentationVersion(sdk.Version()),
+	metric.WithSchemaURL(SchemaURL),
+}
+
+// Tracer is instrumentation for an OTel SDK Tracer.
+type Tracer struct {
+	enabled bool
+
+	live    metric.Int64UpDownCounter
+	started metric.Int64Counter
+}
+
+func NewTracer() (Tracer, error) {
+	if !x.Observability.Enabled() {
+		return Tracer{}, nil
+	}
+	meter := otel.GetMeterProvider().Meter(ScopeName, meterOpts...)
+
+	var err error
+	l, e := otelconv.NewSDKSpanLive(meter)
+	if e != nil {
+		e = fmt.Errorf("failed to create span live metric: %w", e)
+		err = errors.Join(err, e)
+	}
+
+	s, e := otelconv.NewSDKSpanStarted(meter)
+	if e != nil {
+		e = fmt.Errorf("failed to create span started metric: %w", e)
+		err = errors.Join(err, e)
+	}
+
+	return Tracer{enabled: true, live: l.Inst(), started: s.Inst()}, err
+}
+
+func (t Tracer) Enabled() bool { return t.enabled }
+
+func (t Tracer) SpanStarted(ctx context.Context, psc trace.SpanContext, span trace.Span) {
+	key := spanStartedKey{
+		parent:   parentStateNoParent,
+		sampling: samplingStateDrop,
+	}
+
+	if psc.IsValid() {
+		if psc.IsRemote() {
+			key.parent = parentStateRemoteParent
+		} else {
+			key.parent = parentStateLocalParent
+		}
+	}
+
+	if span.IsRecording() {
+		if span.SpanContext().IsSampled() {
+			key.sampling = samplingStateRecordAndSample
+		} else {
+			key.sampling = samplingStateRecordOnly
+		}
+	}
+
+	opts := spanStartedOpts[key]
+	t.started.Add(ctx, 1, opts...)
+}
+
+func (t Tracer) SpanLive(ctx context.Context, span trace.Span) {
+	t.spanLive(ctx, 1, span)
+}
+
+func (t Tracer) SpanEnded(ctx context.Context, span trace.Span) {
+	t.spanLive(ctx, -1, span)
+}
+
+func (t Tracer) spanLive(ctx context.Context, value int64, span trace.Span) {
+	key := spanLiveKey{sampled: span.SpanContext().IsSampled()}
+	opts := spanLiveOpts[key]
+	t.live.Add(ctx, value, opts...)
+}
+
+type parentState int
+
+const (
+	parentStateNoParent parentState = iota
+	parentStateLocalParent
+	parentStateRemoteParent
+)
+
+type samplingState int
+
+const (
+	samplingStateDrop samplingState = iota
+	samplingStateRecordOnly
+	samplingStateRecordAndSample
+)
+
+type spanStartedKey struct {
+	parent   parentState
+	sampling samplingState
+}
+
+var spanStartedOpts = map[spanStartedKey][]metric.AddOption{
+	{
+		parentStateNoParent,
+		samplingStateDrop,
+	}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanStarted{}.AttrSpanParentOrigin(otelconv.SpanParentOriginNone),
+			otelconv.SDKSpanStarted{}.AttrSpanSamplingResult(otelconv.SpanSamplingResultDrop),
+		)),
+	},
+	{
+		parentStateLocalParent,
+		samplingStateDrop,
+	}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanStarted{}.AttrSpanParentOrigin(otelconv.SpanParentOriginLocal),
+			otelconv.SDKSpanStarted{}.AttrSpanSamplingResult(otelconv.SpanSamplingResultDrop),
+		)),
+	},
+	{
+		parentStateRemoteParent,
+		samplingStateDrop,
+	}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanStarted{}.AttrSpanParentOrigin(otelconv.SpanParentOriginRemote),
+			otelconv.SDKSpanStarted{}.AttrSpanSamplingResult(otelconv.SpanSamplingResultDrop),
+		)),
+	},
+
+	{
+		parentStateNoParent,
+		samplingStateRecordOnly,
+	}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanStarted{}.AttrSpanParentOrigin(otelconv.SpanParentOriginNone),
+			otelconv.SDKSpanStarted{}.AttrSpanSamplingResult(otelconv.SpanSamplingResultRecordOnly),
+		)),
+	},
+	{
+		parentStateLocalParent,
+		samplingStateRecordOnly,
+	}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanStarted{}.AttrSpanParentOrigin(otelconv.SpanParentOriginLocal),
+			otelconv.SDKSpanStarted{}.AttrSpanSamplingResult(otelconv.SpanSamplingResultRecordOnly),
+		)),
+	},
+	{
+		parentStateRemoteParent,
+		samplingStateRecordOnly,
+	}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanStarted{}.AttrSpanParentOrigin(otelconv.SpanParentOriginRemote),
+			otelconv.SDKSpanStarted{}.AttrSpanSamplingResult(otelconv.SpanSamplingResultRecordOnly),
+		)),
+	},
+
+	{
+		parentStateNoParent,
+		samplingStateRecordAndSample,
+	}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanStarted{}.AttrSpanParentOrigin(otelconv.SpanParentOriginNone),
+			otelconv.SDKSpanStarted{}.AttrSpanSamplingResult(otelconv.SpanSamplingResultRecordAndSample),
+		)),
+	},
+	{
+		parentStateLocalParent,
+		samplingStateRecordAndSample,
+	}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanStarted{}.AttrSpanParentOrigin(otelconv.SpanParentOriginLocal),
+			otelconv.SDKSpanStarted{}.AttrSpanSamplingResult(otelconv.SpanSamplingResultRecordAndSample),
+		)),
+	},
+	{
+		parentStateRemoteParent,
+		samplingStateRecordAndSample,
+	}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanStarted{}.AttrSpanParentOrigin(otelconv.SpanParentOriginRemote),
+			otelconv.SDKSpanStarted{}.AttrSpanSamplingResult(otelconv.SpanSamplingResultRecordAndSample),
+		)),
+	},
+}
+
+type spanLiveKey struct {
+	sampled bool
+}
+
+var spanLiveOpts = map[spanLiveKey][]metric.AddOption{
+	{true}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanLive{}.AttrSpanSamplingResult(
+				otelconv.SpanSamplingResultRecordAndSample,
+			),
+		)),
+	},
+	{false}: {
+		metric.WithAttributeSet(attribute.NewSet(
+			otelconv.SDKSpanLive{}.AttrSpanSamplingResult(
+				otelconv.SpanSamplingResultRecordOnly,
+			),
+		)),
+	},
+}