1 files changed, 293 insertions, 0 deletions
diff --git a/vendor/go.opentelemetry.io/otel/sdk/trace/sampling.go b/vendor/go.opentelemetry.io/otel/sdk/trace/sampling.go
new file mode 100644
index 000000000..5ee9715d2
--- /dev/null
+++ b/vendor/go.opentelemetry.io/otel/sdk/trace/sampling.go
@@ -0,0 +1,293 @@
+// 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 trace // import "go.opentelemetry.io/otel/sdk/trace"
+
+import (
+	"context"
+	"encoding/binary"
+	"fmt"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// Sampler decides whether a trace should be sampled and exported.
+type Sampler interface {
+	// DO NOT CHANGE: any modification will not be backwards compatible and
+	// must never be done outside of a new major release.
+
+	// ShouldSample returns a SamplingResult based on a decision made from the
+	// passed parameters.
+	ShouldSample(parameters SamplingParameters) SamplingResult
+	// DO NOT CHANGE: any modification will not be backwards compatible and
+	// must never be done outside of a new major release.
+
+	// Description returns information describing the Sampler.
+	Description() string
+	// DO NOT CHANGE: any modification will not be backwards compatible and
+	// must never be done outside of a new major release.
+}
+
+// SamplingParameters contains the values passed to a Sampler.
+type SamplingParameters struct {
+	ParentContext context.Context
+	TraceID       trace.TraceID
+	Name          string
+	Kind          trace.SpanKind
+	Attributes    []attribute.KeyValue
+	Links         []trace.Link
+}
+
+// SamplingDecision indicates whether a span is dropped, recorded and/or sampled.
+type SamplingDecision uint8
+
+// Valid sampling decisions.
+const (
+	// Drop will not record the span and all attributes/events will be dropped.
+	Drop SamplingDecision = iota
+
+	// Record indicates the span's `IsRecording() == true`, but `Sampled` flag
+	// *must not* be set.
+	RecordOnly
+
+	// RecordAndSample has span's `IsRecording() == true` and `Sampled` flag
+	// *must* be set.
+	RecordAndSample
+)
+
+// SamplingResult conveys a SamplingDecision, set of Attributes and a Tracestate.
+type SamplingResult struct {
+	Decision   SamplingDecision
+	Attributes []attribute.KeyValue
+	Tracestate trace.TraceState
+}
+
+type traceIDRatioSampler struct {
+	traceIDUpperBound uint64
+	description       string
+}
+
+func (ts traceIDRatioSampler) ShouldSample(p SamplingParameters) SamplingResult {
+	psc := trace.SpanContextFromContext(p.ParentContext)
+	x := binary.BigEndian.Uint64(p.TraceID[8:16]) >> 1
+	if x < ts.traceIDUpperBound {
+		return SamplingResult{
+			Decision:   RecordAndSample,
+			Tracestate: psc.TraceState(),
+		}
+	}
+	return SamplingResult{
+		Decision:   Drop,
+		Tracestate: psc.TraceState(),
+	}
+}
+
+func (ts traceIDRatioSampler) Description() string {
+	return ts.description
+}
+
+// TraceIDRatioBased samples a given fraction of traces. Fractions >= 1 will
+// always sample. Fractions < 0 are treated as zero. To respect the
+// parent trace's `SampledFlag`, the `TraceIDRatioBased` sampler should be used
+// as a delegate of a `Parent` sampler.
+//
+//nolint:revive // revive complains about stutter of `trace.TraceIDRatioBased`
+func TraceIDRatioBased(fraction float64) Sampler {
+	if fraction >= 1 {
+		return AlwaysSample()
+	}
+
+	if fraction <= 0 {
+		fraction = 0
+	}
+
+	return &traceIDRatioSampler{
+		traceIDUpperBound: uint64(fraction * (1 << 63)),
+		description:       fmt.Sprintf("TraceIDRatioBased{%g}", fraction),
+	}
+}
+
+type alwaysOnSampler struct{}
+
+func (as alwaysOnSampler) ShouldSample(p SamplingParameters) SamplingResult {
+	return SamplingResult{
+		Decision:   RecordAndSample,
+		Tracestate: trace.SpanContextFromContext(p.ParentContext).TraceState(),
+	}
+}
+
+func (as alwaysOnSampler) Description() string {
+	return "AlwaysOnSampler"
+}
+
+// AlwaysSample returns a Sampler that samples every trace.
+// Be careful about using this sampler in a production application with
+// significant traffic: a new trace will be started and exported for every
+// request.
+func AlwaysSample() Sampler {
+	return alwaysOnSampler{}
+}
+
+type alwaysOffSampler struct{}
+
+func (as alwaysOffSampler) ShouldSample(p SamplingParameters) SamplingResult {
+	return SamplingResult{
+		Decision:   Drop,
+		Tracestate: trace.SpanContextFromContext(p.ParentContext).TraceState(),
+	}
+}
+
+func (as alwaysOffSampler) Description() string {
+	return "AlwaysOffSampler"
+}
+
+// NeverSample returns a Sampler that samples no traces.
+func NeverSample() Sampler {
+	return alwaysOffSampler{}
+}
+
+// ParentBased returns a composite sampler which behaves differently,
+// based on the parent of the span. If the span has no parent,
+// the root(Sampler) is used to make sampling decision. If the span has
+// a parent, depending on whether the parent is remote and whether it
+// is sampled, one of the following samplers will apply:
+//   - remoteParentSampled(Sampler) (default: AlwaysOn)
+//   - remoteParentNotSampled(Sampler) (default: AlwaysOff)
+//   - localParentSampled(Sampler) (default: AlwaysOn)
+//   - localParentNotSampled(Sampler) (default: AlwaysOff)
+func ParentBased(root Sampler, samplers ...ParentBasedSamplerOption) Sampler {
+	return parentBased{
+		root:   root,
+		config: configureSamplersForParentBased(samplers),
+	}
+}
+
+type parentBased struct {
+	root   Sampler
+	config samplerConfig
+}
+
+func configureSamplersForParentBased(samplers []ParentBasedSamplerOption) samplerConfig {
+	c := samplerConfig{
+		remoteParentSampled:    AlwaysSample(),
+		remoteParentNotSampled: NeverSample(),
+		localParentSampled:     AlwaysSample(),
+		localParentNotSampled:  NeverSample(),
+	}
+
+	for _, so := range samplers {
+		c = so.apply(c)
+	}
+
+	return c
+}
+
+// samplerConfig is a group of options for parentBased sampler.
+type samplerConfig struct {
+	remoteParentSampled, remoteParentNotSampled Sampler
+	localParentSampled, localParentNotSampled   Sampler
+}
+
+// ParentBasedSamplerOption configures the sampler for a particular sampling case.
+type ParentBasedSamplerOption interface {
+	apply(samplerConfig) samplerConfig
+}
+
+// WithRemoteParentSampled sets the sampler for the case of sampled remote parent.
+func WithRemoteParentSampled(s Sampler) ParentBasedSamplerOption {
+	return remoteParentSampledOption{s}
+}
+
+type remoteParentSampledOption struct {
+	s Sampler
+}
+
+func (o remoteParentSampledOption) apply(config samplerConfig) samplerConfig {
+	config.remoteParentSampled = o.s
+	return config
+}
+
+// WithRemoteParentNotSampled sets the sampler for the case of remote parent
+// which is not sampled.
+func WithRemoteParentNotSampled(s Sampler) ParentBasedSamplerOption {
+	return remoteParentNotSampledOption{s}
+}
+
+type remoteParentNotSampledOption struct {
+	s Sampler
+}
+
+func (o remoteParentNotSampledOption) apply(config samplerConfig) samplerConfig {
+	config.remoteParentNotSampled = o.s
+	return config
+}
+
+// WithLocalParentSampled sets the sampler for the case of sampled local parent.
+func WithLocalParentSampled(s Sampler) ParentBasedSamplerOption {
+	return localParentSampledOption{s}
+}
+
+type localParentSampledOption struct {
+	s Sampler
+}
+
+func (o localParentSampledOption) apply(config samplerConfig) samplerConfig {
+	config.localParentSampled = o.s
+	return config
+}
+
+// WithLocalParentNotSampled sets the sampler for the case of local parent
+// which is not sampled.
+func WithLocalParentNotSampled(s Sampler) ParentBasedSamplerOption {
+	return localParentNotSampledOption{s}
+}
+
+type localParentNotSampledOption struct {
+	s Sampler
+}
+
+func (o localParentNotSampledOption) apply(config samplerConfig) samplerConfig {
+	config.localParentNotSampled = o.s
+	return config
+}
+
+func (pb parentBased) ShouldSample(p SamplingParameters) SamplingResult {
+	psc := trace.SpanContextFromContext(p.ParentContext)
+	if psc.IsValid() {
+		if psc.IsRemote() {
+			if psc.IsSampled() {
+				return pb.config.remoteParentSampled.ShouldSample(p)
+			}
+			return pb.config.remoteParentNotSampled.ShouldSample(p)
+		}
+
+		if psc.IsSampled() {
+			return pb.config.localParentSampled.ShouldSample(p)
+		}
+		return pb.config.localParentNotSampled.ShouldSample(p)
+	}
+	return pb.root.ShouldSample(p)
+}
+
+func (pb parentBased) Description() string {
+	return fmt.Sprintf("ParentBased{root:%s,remoteParentSampled:%s,"+
+		"remoteParentNotSampled:%s,localParentSampled:%s,localParentNotSampled:%s}",
+		pb.root.Description(),
+		pb.config.remoteParentSampled.Description(),
+		pb.config.remoteParentNotSampled.Description(),
+		pb.config.localParentSampled.Description(),
+		pb.config.localParentNotSampled.Description(),
+	)
+}