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// Copyright (c) 2017 Uber Technologies, Inc.
//
// 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 jaeger
import (
"fmt"
"math"
"strings"
"sync"
"github.com/uber/jaeger-client-go/thrift-gen/sampling"
"github.com/uber/jaeger-client-go/utils"
)
const (
defaultMaxOperations = 2000
)
// Sampler decides whether a new trace should be sampled or not.
type Sampler interface {
// IsSampled decides whether a trace with given `id` and `operation`
// should be sampled. This function will also return the tags that
// can be used to identify the type of sampling that was applied to
// the root span. Most simple samplers would return two tags,
// sampler.type and sampler.param, similar to those used in the Configuration
IsSampled(id TraceID, operation string) (sampled bool, tags []Tag)
// Close does a clean shutdown of the sampler, stopping any background
// go-routines it may have started.
Close()
// Equal checks if the `other` sampler is functionally equivalent
// to this sampler.
// TODO (breaking change) remove this function. See PerOperationSampler.Equals for explanation.
Equal(other Sampler) bool
}
// -----------------------
// ConstSampler is a sampler that always makes the same decision.
type ConstSampler struct {
legacySamplerV1Base
Decision bool
tags []Tag
}
// NewConstSampler creates a ConstSampler.
func NewConstSampler(sample bool) *ConstSampler {
tags := []Tag{
{key: SamplerTypeTagKey, value: SamplerTypeConst},
{key: SamplerParamTagKey, value: sample},
}
s := &ConstSampler{
Decision: sample,
tags: tags,
}
s.delegate = s.IsSampled
return s
}
// IsSampled implements IsSampled() of Sampler.
func (s *ConstSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
return s.Decision, s.tags
}
// Close implements Close() of Sampler.
func (s *ConstSampler) Close() {
// nothing to do
}
// Equal implements Equal() of Sampler.
func (s *ConstSampler) Equal(other Sampler) bool {
if o, ok := other.(*ConstSampler); ok {
return s.Decision == o.Decision
}
return false
}
// String is used to log sampler details.
func (s *ConstSampler) String() string {
return fmt.Sprintf("ConstSampler(decision=%t)", s.Decision)
}
// -----------------------
// ProbabilisticSampler is a sampler that randomly samples a certain percentage
// of traces.
type ProbabilisticSampler struct {
legacySamplerV1Base
samplingRate float64
samplingBoundary uint64
tags []Tag
}
const maxRandomNumber = ^(uint64(1) << 63) // i.e. 0x7fffffffffffffff
// NewProbabilisticSampler creates a sampler that randomly samples a certain percentage of traces specified by the
// samplingRate, in the range between 0.0 and 1.0.
//
// It relies on the fact that new trace IDs are 63bit random numbers themselves, thus making the sampling decision
// without generating a new random number, but simply calculating if traceID < (samplingRate * 2^63).
// TODO remove the error from this function for next major release
func NewProbabilisticSampler(samplingRate float64) (*ProbabilisticSampler, error) {
if samplingRate < 0.0 || samplingRate > 1.0 {
return nil, fmt.Errorf("Sampling Rate must be between 0.0 and 1.0, received %f", samplingRate)
}
return newProbabilisticSampler(samplingRate), nil
}
func newProbabilisticSampler(samplingRate float64) *ProbabilisticSampler {
s := new(ProbabilisticSampler)
s.delegate = s.IsSampled
return s.init(samplingRate)
}
func (s *ProbabilisticSampler) init(samplingRate float64) *ProbabilisticSampler {
s.samplingRate = math.Max(0.0, math.Min(samplingRate, 1.0))
s.samplingBoundary = uint64(float64(maxRandomNumber) * s.samplingRate)
s.tags = []Tag{
{key: SamplerTypeTagKey, value: SamplerTypeProbabilistic},
{key: SamplerParamTagKey, value: s.samplingRate},
}
return s
}
// SamplingRate returns the sampling probability this sampled was constructed with.
func (s *ProbabilisticSampler) SamplingRate() float64 {
return s.samplingRate
}
// IsSampled implements IsSampled() of Sampler.
func (s *ProbabilisticSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
return s.samplingBoundary >= id.Low&maxRandomNumber, s.tags
}
// Close implements Close() of Sampler.
func (s *ProbabilisticSampler) Close() {
// nothing to do
}
// Equal implements Equal() of Sampler.
func (s *ProbabilisticSampler) Equal(other Sampler) bool {
if o, ok := other.(*ProbabilisticSampler); ok {
return s.samplingBoundary == o.samplingBoundary
}
return false
}
// Update modifies in-place the sampling rate. Locking must be done externally.
func (s *ProbabilisticSampler) Update(samplingRate float64) error {
if samplingRate < 0.0 || samplingRate > 1.0 {
return fmt.Errorf("Sampling Rate must be between 0.0 and 1.0, received %f", samplingRate)
}
s.init(samplingRate)
return nil
}
// String is used to log sampler details.
func (s *ProbabilisticSampler) String() string {
return fmt.Sprintf("ProbabilisticSampler(samplingRate=%v)", s.samplingRate)
}
// -----------------------
// RateLimitingSampler samples at most maxTracesPerSecond. The distribution of sampled traces follows
// burstiness of the service, i.e. a service with uniformly distributed requests will have those
// requests sampled uniformly as well, but if requests are bursty, especially sub-second, then a
// number of sequential requests can be sampled each second.
type RateLimitingSampler struct {
legacySamplerV1Base
maxTracesPerSecond float64
rateLimiter *utils.ReconfigurableRateLimiter
tags []Tag
}
// NewRateLimitingSampler creates new RateLimitingSampler.
func NewRateLimitingSampler(maxTracesPerSecond float64) *RateLimitingSampler {
s := new(RateLimitingSampler)
s.delegate = s.IsSampled
return s.init(maxTracesPerSecond)
}
func (s *RateLimitingSampler) init(maxTracesPerSecond float64) *RateLimitingSampler {
if s.rateLimiter == nil {
s.rateLimiter = utils.NewRateLimiter(maxTracesPerSecond, math.Max(maxTracesPerSecond, 1.0))
} else {
s.rateLimiter.Update(maxTracesPerSecond, math.Max(maxTracesPerSecond, 1.0))
}
s.maxTracesPerSecond = maxTracesPerSecond
s.tags = []Tag{
{key: SamplerTypeTagKey, value: SamplerTypeRateLimiting},
{key: SamplerParamTagKey, value: maxTracesPerSecond},
}
return s
}
// IsSampled implements IsSampled() of Sampler.
func (s *RateLimitingSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
return s.rateLimiter.CheckCredit(1.0), s.tags
}
// Update reconfigures the rate limiter, while preserving its accumulated balance.
// Locking must be done externally.
func (s *RateLimitingSampler) Update(maxTracesPerSecond float64) {
if s.maxTracesPerSecond != maxTracesPerSecond {
s.init(maxTracesPerSecond)
}
}
// Close does nothing.
func (s *RateLimitingSampler) Close() {
// nothing to do
}
// Equal compares with another sampler.
func (s *RateLimitingSampler) Equal(other Sampler) bool {
if o, ok := other.(*RateLimitingSampler); ok {
return s.maxTracesPerSecond == o.maxTracesPerSecond
}
return false
}
// String is used to log sampler details.
func (s *RateLimitingSampler) String() string {
return fmt.Sprintf("RateLimitingSampler(maxTracesPerSecond=%v)", s.maxTracesPerSecond)
}
// -----------------------
// GuaranteedThroughputProbabilisticSampler is a sampler that leverages both ProbabilisticSampler and
// RateLimitingSampler. The RateLimitingSampler is used as a guaranteed lower bound sampler such that
// every operation is sampled at least once in a time interval defined by the lowerBound. ie a lowerBound
// of 1.0 / (60 * 10) will sample an operation at least once every 10 minutes.
//
// The ProbabilisticSampler is given higher priority when tags are emitted, ie. if IsSampled() for both
// samplers return true, the tags for ProbabilisticSampler will be used.
type GuaranteedThroughputProbabilisticSampler struct {
probabilisticSampler *ProbabilisticSampler
lowerBoundSampler *RateLimitingSampler
tags []Tag
samplingRate float64
lowerBound float64
}
// NewGuaranteedThroughputProbabilisticSampler returns a delegating sampler that applies both
// ProbabilisticSampler and RateLimitingSampler.
func NewGuaranteedThroughputProbabilisticSampler(
lowerBound, samplingRate float64,
) (*GuaranteedThroughputProbabilisticSampler, error) {
return newGuaranteedThroughputProbabilisticSampler(lowerBound, samplingRate), nil
}
func newGuaranteedThroughputProbabilisticSampler(lowerBound, samplingRate float64) *GuaranteedThroughputProbabilisticSampler {
s := &GuaranteedThroughputProbabilisticSampler{
lowerBoundSampler: NewRateLimitingSampler(lowerBound),
lowerBound: lowerBound,
}
s.setProbabilisticSampler(samplingRate)
return s
}
func (s *GuaranteedThroughputProbabilisticSampler) setProbabilisticSampler(samplingRate float64) {
if s.probabilisticSampler == nil {
s.probabilisticSampler = newProbabilisticSampler(samplingRate)
} else if s.samplingRate != samplingRate {
s.probabilisticSampler.init(samplingRate)
}
// since we don't validate samplingRate, sampler may have clamped it to [0, 1] interval
samplingRate = s.probabilisticSampler.SamplingRate()
if s.samplingRate != samplingRate || s.tags == nil {
s.samplingRate = s.probabilisticSampler.SamplingRate()
s.tags = []Tag{
{key: SamplerTypeTagKey, value: SamplerTypeLowerBound},
{key: SamplerParamTagKey, value: s.samplingRate},
}
}
}
// IsSampled implements IsSampled() of Sampler.
func (s *GuaranteedThroughputProbabilisticSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
if sampled, tags := s.probabilisticSampler.IsSampled(id, operation); sampled {
s.lowerBoundSampler.IsSampled(id, operation)
return true, tags
}
sampled, _ := s.lowerBoundSampler.IsSampled(id, operation)
return sampled, s.tags
}
// Close implements Close() of Sampler.
func (s *GuaranteedThroughputProbabilisticSampler) Close() {
s.probabilisticSampler.Close()
s.lowerBoundSampler.Close()
}
// Equal implements Equal() of Sampler.
func (s *GuaranteedThroughputProbabilisticSampler) Equal(other Sampler) bool {
// NB The Equal() function is expensive and will be removed. See PerOperationSampler.Equal() for
// more information.
return false
}
// this function should only be called while holding a Write lock
func (s *GuaranteedThroughputProbabilisticSampler) update(lowerBound, samplingRate float64) {
s.setProbabilisticSampler(samplingRate)
if s.lowerBound != lowerBound {
s.lowerBoundSampler.Update(lowerBound)
s.lowerBound = lowerBound
}
}
func (s GuaranteedThroughputProbabilisticSampler) String() string {
return fmt.Sprintf("GuaranteedThroughputProbabilisticSampler(lowerBound=%f, samplingRate=%f)", s.lowerBound, s.samplingRate)
}
// -----------------------
// PerOperationSampler is a delegating sampler that applies GuaranteedThroughputProbabilisticSampler
// on a per-operation basis.
type PerOperationSampler struct {
sync.RWMutex
samplers map[string]*GuaranteedThroughputProbabilisticSampler
defaultSampler *ProbabilisticSampler
lowerBound float64
maxOperations int
// see description in PerOperationSamplerParams
operationNameLateBinding bool
}
// NewAdaptiveSampler returns a new PerOperationSampler.
// Deprecated: please use NewPerOperationSampler.
func NewAdaptiveSampler(strategies *sampling.PerOperationSamplingStrategies, maxOperations int) (*PerOperationSampler, error) {
return NewPerOperationSampler(PerOperationSamplerParams{
MaxOperations: maxOperations,
Strategies: strategies,
}), nil
}
// PerOperationSamplerParams defines parameters when creating PerOperationSampler.
type PerOperationSamplerParams struct {
// Max number of operations that will be tracked. Other operations will be given default strategy.
MaxOperations int
// Opt-in feature for applications that require late binding of span name via explicit call to SetOperationName.
// When this feature is enabled, the sampler will return retryable=true from OnCreateSpan(), thus leaving
// the sampling decision as non-final (and the span as writeable). This may lead to degraded performance
// in applications that always provide the correct span name on trace creation.
//
// For backwards compatibility this option is off by default.
OperationNameLateBinding bool
// Initial configuration of the sampling strategies (usually retrieved from the backend by Remote Sampler).
Strategies *sampling.PerOperationSamplingStrategies
}
// NewPerOperationSampler returns a new PerOperationSampler.
func NewPerOperationSampler(params PerOperationSamplerParams) *PerOperationSampler {
if params.MaxOperations <= 0 {
params.MaxOperations = defaultMaxOperations
}
samplers := make(map[string]*GuaranteedThroughputProbabilisticSampler)
for _, strategy := range params.Strategies.PerOperationStrategies {
sampler := newGuaranteedThroughputProbabilisticSampler(
params.Strategies.DefaultLowerBoundTracesPerSecond,
strategy.ProbabilisticSampling.SamplingRate,
)
samplers[strategy.Operation] = sampler
}
return &PerOperationSampler{
samplers: samplers,
defaultSampler: newProbabilisticSampler(params.Strategies.DefaultSamplingProbability),
lowerBound: params.Strategies.DefaultLowerBoundTracesPerSecond,
maxOperations: params.MaxOperations,
operationNameLateBinding: params.OperationNameLateBinding,
}
}
// IsSampled is not used and only exists to match Sampler V1 API.
// TODO (breaking change) remove when upgrading everything to SamplerV2
func (s *PerOperationSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
return false, nil
}
func (s *PerOperationSampler) trySampling(span *Span, operationName string) (bool, []Tag) {
samplerV1 := s.getSamplerForOperation(operationName)
var sampled bool
var tags []Tag
if span.context.samplingState.isLocalRootSpan(span.context.spanID) {
sampled, tags = samplerV1.IsSampled(span.context.TraceID(), operationName)
}
return sampled, tags
}
// OnCreateSpan implements OnCreateSpan of SamplerV2.
func (s *PerOperationSampler) OnCreateSpan(span *Span) SamplingDecision {
sampled, tags := s.trySampling(span, span.OperationName())
return SamplingDecision{Sample: sampled, Retryable: s.operationNameLateBinding, Tags: tags}
}
// OnSetOperationName implements OnSetOperationName of SamplerV2.
func (s *PerOperationSampler) OnSetOperationName(span *Span, operationName string) SamplingDecision {
sampled, tags := s.trySampling(span, operationName)
return SamplingDecision{Sample: sampled, Retryable: false, Tags: tags}
}
// OnSetTag implements OnSetTag of SamplerV2.
func (s *PerOperationSampler) OnSetTag(span *Span, key string, value interface{}) SamplingDecision {
return SamplingDecision{Sample: false, Retryable: true}
}
// OnFinishSpan implements OnFinishSpan of SamplerV2.
func (s *PerOperationSampler) OnFinishSpan(span *Span) SamplingDecision {
return SamplingDecision{Sample: false, Retryable: true}
}
func (s *PerOperationSampler) getSamplerForOperation(operation string) Sampler {
s.RLock()
sampler, ok := s.samplers[operation]
if ok {
defer s.RUnlock()
return sampler
}
s.RUnlock()
s.Lock()
defer s.Unlock()
// Check if sampler has already been created
sampler, ok = s.samplers[operation]
if ok {
return sampler
}
// Store only up to maxOperations of unique ops.
if len(s.samplers) >= s.maxOperations {
return s.defaultSampler
}
newSampler := newGuaranteedThroughputProbabilisticSampler(s.lowerBound, s.defaultSampler.SamplingRate())
s.samplers[operation] = newSampler
return newSampler
}
// Close invokes Close on all underlying samplers.
func (s *PerOperationSampler) Close() {
s.Lock()
defer s.Unlock()
for _, sampler := range s.samplers {
sampler.Close()
}
s.defaultSampler.Close()
}
func (s *PerOperationSampler) String() string {
var sb strings.Builder
fmt.Fprintf(&sb, "PerOperationSampler(defaultSampler=%v, ", s.defaultSampler)
fmt.Fprintf(&sb, "lowerBound=%f, ", s.lowerBound)
fmt.Fprintf(&sb, "maxOperations=%d, ", s.maxOperations)
fmt.Fprintf(&sb, "operationNameLateBinding=%t, ", s.operationNameLateBinding)
fmt.Fprintf(&sb, "numOperations=%d,\n", len(s.samplers))
fmt.Fprintf(&sb, "samplers=[")
for operationName, sampler := range s.samplers {
fmt.Fprintf(&sb, "\n(operationName=%s, sampler=%v)", operationName, sampler)
}
fmt.Fprintf(&sb, "])")
return sb.String()
}
// Equal is not used.
// TODO (breaking change) remove this in the future
func (s *PerOperationSampler) Equal(other Sampler) bool {
// NB The Equal() function is overly expensive for PerOperationSampler since it's composed of multiple
// samplers which all need to be initialized before this function can be called for a comparison.
// Therefore, PerOperationSampler uses the update() function to only alter the samplers that need
// changing. Hence this function always returns false so that the update function can be called.
// Once the Equal() function is removed from the Sampler API, this will no longer be needed.
return false
}
func (s *PerOperationSampler) update(strategies *sampling.PerOperationSamplingStrategies) {
s.Lock()
defer s.Unlock()
newSamplers := map[string]*GuaranteedThroughputProbabilisticSampler{}
for _, strategy := range strategies.PerOperationStrategies {
operation := strategy.Operation
samplingRate := strategy.ProbabilisticSampling.SamplingRate
lowerBound := strategies.DefaultLowerBoundTracesPerSecond
if sampler, ok := s.samplers[operation]; ok {
sampler.update(lowerBound, samplingRate)
newSamplers[operation] = sampler
} else {
sampler := newGuaranteedThroughputProbabilisticSampler(
lowerBound,
samplingRate,
)
newSamplers[operation] = sampler
}
}
s.lowerBound = strategies.DefaultLowerBoundTracesPerSecond
if s.defaultSampler.SamplingRate() != strategies.DefaultSamplingProbability {
s.defaultSampler = newProbabilisticSampler(strategies.DefaultSamplingProbability)
}
s.samplers = newSamplers
}