cloudflared-mirror/vendor/go.opentelemetry.io/otel/sdk/trace/sampling.go

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// 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.
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const (
// Drop will not record the span and all attributes/events will be dropped.
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Drop SamplingDecision = iota
// Record indicates the span's `IsRecording() == true`, but `Sampled` flag
// *must not* be set.
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RecordOnly
// RecordAndSample has span's `IsRecording() == true` and `Sampled` flag
// *must* be set.
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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
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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.
//
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//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 sampler decorator which behaves differently,
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// based on the parent of the span. If the span has no parent,
// the decorated sampler is used to make sampling decision. If the span has
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// 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)
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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(),
)
}