1 files changed, 556 insertions, 0 deletions
diff --git a/vendor/github.com/uber/jaeger-client-go/sampler.go b/vendor/github.com/uber/jaeger-client-go/sampler.go
new file mode 100644
index 000000000..e6a32b383
--- /dev/null
+++ b/vendor/github.com/uber/jaeger-client-go/sampler.go
@@ -0,0 +1,556 @@
+// 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"
+	"net/url"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/uber/jaeger-client-go/log"
+	"github.com/uber/jaeger-client-go/thrift-gen/sampling"
+	"github.com/uber/jaeger-client-go/utils"
+)
+
+const (
+	defaultSamplingServerURL       = "http://localhost:5778/sampling"
+	defaultSamplingRefreshInterval = time.Minute
+	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 remove this function. This function is used to determine if 2 samplers are equivalent
+	// which does not bode well with the adaptive sampler which has to create all the composite samplers
+	// for the comparison to occur. This is expensive to do if only one sampler has changed.
+	Equal(other Sampler) bool
+}
+
+// -----------------------
+
+// ConstSampler is a sampler that always makes the same decision.
+type ConstSampler struct {
+	Decision bool
+	tags     []Tag
+}
+
+// NewConstSampler creates a ConstSampler.
+func NewConstSampler(sample bool) Sampler {
+	tags := []Tag{
+		{key: SamplerTypeTagKey, value: SamplerTypeConst},
+		{key: SamplerParamTagKey, value: sample},
+	}
+	return &ConstSampler{Decision: sample, tags: tags}
+}
+
+// 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
+}
+
+// -----------------------
+
+// ProbabilisticSampler is a sampler that randomly samples a certain percentage
+// of traces.
+type ProbabilisticSampler struct {
+	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 {
+	samplingRate = math.Max(0.0, math.Min(samplingRate, 1.0))
+	tags := []Tag{
+		{key: SamplerTypeTagKey, value: SamplerTypeProbabilistic},
+		{key: SamplerParamTagKey, value: samplingRate},
+	}
+	return &ProbabilisticSampler{
+		samplingRate:     samplingRate,
+		samplingBoundary: uint64(float64(maxRandomNumber) * samplingRate),
+		tags:             tags,
+	}
+}
+
+// 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, 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
+}
+
+// -----------------------
+
+type rateLimitingSampler struct {
+	maxTracesPerSecond float64
+	rateLimiter        utils.RateLimiter
+	tags               []Tag
+}
+
+// NewRateLimitingSampler creates a sampler that 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.
+func NewRateLimitingSampler(maxTracesPerSecond float64) Sampler {
+	tags := []Tag{
+		{key: SamplerTypeTagKey, value: SamplerTypeRateLimiting},
+		{key: SamplerParamTagKey, value: maxTracesPerSecond},
+	}
+	return &rateLimitingSampler{
+		maxTracesPerSecond: maxTracesPerSecond,
+		rateLimiter:        utils.NewRateLimiter(maxTracesPerSecond, math.Max(maxTracesPerSecond, 1.0)),
+		tags:               tags,
+	}
+}
+
+// IsSampled implements IsSampled() of Sampler.
+func (s *rateLimitingSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
+	return s.rateLimiter.CheckCredit(1.0), s.tags
+}
+
+func (s *rateLimitingSampler) Close() {
+	// nothing to do
+}
+
+func (s *rateLimitingSampler) Equal(other Sampler) bool {
+	if o, ok := other.(*rateLimitingSampler); ok {
+		return s.maxTracesPerSecond == o.maxTracesPerSecond
+	}
+	return false
+}
+
+// -----------------------
+
+// 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    Sampler
+	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.samplingRate != samplingRate {
+		s.probabilisticSampler = newProbabilisticSampler(samplingRate)
+		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 adaptiveSampler.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 = NewRateLimitingSampler(lowerBound)
+		s.lowerBound = lowerBound
+	}
+}
+
+// -----------------------
+
+type adaptiveSampler struct {
+	sync.RWMutex
+
+	samplers       map[string]*GuaranteedThroughputProbabilisticSampler
+	defaultSampler *ProbabilisticSampler
+	lowerBound     float64
+	maxOperations  int
+}
+
+// NewAdaptiveSampler returns a delegating sampler that applies both probabilisticSampler and
+// rateLimitingSampler via the guaranteedThroughputProbabilisticSampler. This sampler keeps track of all
+// operations and delegates calls to the respective guaranteedThroughputProbabilisticSampler.
+func NewAdaptiveSampler(strategies *sampling.PerOperationSamplingStrategies, maxOperations int) (Sampler, error) {
+	return newAdaptiveSampler(strategies, maxOperations), nil
+}
+
+func newAdaptiveSampler(strategies *sampling.PerOperationSamplingStrategies, maxOperations int) Sampler {
+	samplers := make(map[string]*GuaranteedThroughputProbabilisticSampler)
+	for _, strategy := range strategies.PerOperationStrategies {
+		sampler := newGuaranteedThroughputProbabilisticSampler(
+			strategies.DefaultLowerBoundTracesPerSecond,
+			strategy.ProbabilisticSampling.SamplingRate,
+		)
+		samplers[strategy.Operation] = sampler
+	}
+	return &adaptiveSampler{
+		samplers:       samplers,
+		defaultSampler: newProbabilisticSampler(strategies.DefaultSamplingProbability),
+		lowerBound:     strategies.DefaultLowerBoundTracesPerSecond,
+		maxOperations:  maxOperations,
+	}
+}
+
+func (s *adaptiveSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
+	s.RLock()
+	sampler, ok := s.samplers[operation]
+	if ok {
+		defer s.RUnlock()
+		return sampler.IsSampled(id, operation)
+	}
+	s.RUnlock()
+	s.Lock()
+	defer s.Unlock()
+
+	// Check if sampler has already been created
+	sampler, ok = s.samplers[operation]
+	if ok {
+		return sampler.IsSampled(id, operation)
+	}
+	// Store only up to maxOperations of unique ops.
+	if len(s.samplers) >= s.maxOperations {
+		return s.defaultSampler.IsSampled(id, operation)
+	}
+	newSampler := newGuaranteedThroughputProbabilisticSampler(s.lowerBound, s.defaultSampler.SamplingRate())
+	s.samplers[operation] = newSampler
+	return newSampler.IsSampled(id, operation)
+}
+
+func (s *adaptiveSampler) Close() {
+	s.Lock()
+	defer s.Unlock()
+	for _, sampler := range s.samplers {
+		sampler.Close()
+	}
+	s.defaultSampler.Close()
+}
+
+func (s *adaptiveSampler) Equal(other Sampler) bool {
+	// NB The Equal() function is overly expensive for adaptiveSampler since it's composed of multiple
+	// samplers which all need to be initialized before this function can be called for a comparison.
+	// Therefore, adaptiveSampler 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 *adaptiveSampler) update(strategies *sampling.PerOperationSamplingStrategies) {
+	s.Lock()
+	defer s.Unlock()
+	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)
+		} else {
+			sampler := newGuaranteedThroughputProbabilisticSampler(
+				lowerBound,
+				samplingRate,
+			)
+			s.samplers[operation] = sampler
+		}
+	}
+	s.lowerBound = strategies.DefaultLowerBoundTracesPerSecond
+	if s.defaultSampler.SamplingRate() != strategies.DefaultSamplingProbability {
+		s.defaultSampler = newProbabilisticSampler(strategies.DefaultSamplingProbability)
+	}
+}
+
+// -----------------------
+
+// RemotelyControlledSampler is a delegating sampler that polls a remote server
+// for the appropriate sampling strategy, constructs a corresponding sampler and
+// delegates to it for sampling decisions.
+type RemotelyControlledSampler struct {
+	// These fields must be first in the struct because `sync/atomic` expects 64-bit alignment.
+	// Cf. https://github.com/uber/jaeger-client-go/issues/155, https://goo.gl/zW7dgq
+	closed int64 // 0 - not closed, 1 - closed
+
+	sync.RWMutex
+	samplerOptions
+
+	serviceName string
+	manager     sampling.SamplingManager
+	doneChan    chan *sync.WaitGroup
+}
+
+type httpSamplingManager struct {
+	serverURL string
+}
+
+func (s *httpSamplingManager) GetSamplingStrategy(serviceName string) (*sampling.SamplingStrategyResponse, error) {
+	var out sampling.SamplingStrategyResponse
+	v := url.Values{}
+	v.Set("service", serviceName)
+	if err := utils.GetJSON(s.serverURL+"?"+v.Encode(), &out); err != nil {
+		return nil, err
+	}
+	return &out, nil
+}
+
+// NewRemotelyControlledSampler creates a sampler that periodically pulls
+// the sampling strategy from an HTTP sampling server (e.g. jaeger-agent).
+func NewRemotelyControlledSampler(
+	serviceName string,
+	opts ...SamplerOption,
+) *RemotelyControlledSampler {
+	options := applySamplerOptions(opts...)
+	sampler := &RemotelyControlledSampler{
+		samplerOptions: options,
+		serviceName:    serviceName,
+		manager:        &httpSamplingManager{serverURL: options.samplingServerURL},
+		doneChan:       make(chan *sync.WaitGroup),
+	}
+	go sampler.pollController()
+	return sampler
+}
+
+func applySamplerOptions(opts ...SamplerOption) samplerOptions {
+	options := samplerOptions{}
+	for _, option := range opts {
+		option(&options)
+	}
+	if options.sampler == nil {
+		options.sampler = newProbabilisticSampler(0.001)
+	}
+	if options.logger == nil {
+		options.logger = log.NullLogger
+	}
+	if options.maxOperations <= 0 {
+		options.maxOperations = defaultMaxOperations
+	}
+	if options.samplingServerURL == "" {
+		options.samplingServerURL = defaultSamplingServerURL
+	}
+	if options.metrics == nil {
+		options.metrics = NewNullMetrics()
+	}
+	if options.samplingRefreshInterval <= 0 {
+		options.samplingRefreshInterval = defaultSamplingRefreshInterval
+	}
+	return options
+}
+
+// IsSampled implements IsSampled() of Sampler.
+func (s *RemotelyControlledSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
+	s.RLock()
+	defer s.RUnlock()
+	return s.sampler.IsSampled(id, operation)
+}
+
+// Close implements Close() of Sampler.
+func (s *RemotelyControlledSampler) Close() {
+	if swapped := atomic.CompareAndSwapInt64(&s.closed, 0, 1); !swapped {
+		s.logger.Error("Repeated attempt to close the sampler is ignored")
+		return
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	s.doneChan <- &wg
+	wg.Wait()
+}
+
+// Equal implements Equal() of Sampler.
+func (s *RemotelyControlledSampler) Equal(other Sampler) bool {
+	// NB The Equal() function is expensive and will be removed. See adaptiveSampler.Equal() for
+	// more information.
+	if o, ok := other.(*RemotelyControlledSampler); ok {
+		s.RLock()
+		o.RLock()
+		defer s.RUnlock()
+		defer o.RUnlock()
+		return s.sampler.Equal(o.sampler)
+	}
+	return false
+}
+
+func (s *RemotelyControlledSampler) pollController() {
+	ticker := time.NewTicker(s.samplingRefreshInterval)
+	defer ticker.Stop()
+	s.pollControllerWithTicker(ticker)
+}
+
+func (s *RemotelyControlledSampler) pollControllerWithTicker(ticker *time.Ticker) {
+	for {
+		select {
+		case <-ticker.C:
+			s.updateSampler()
+		case wg := <-s.doneChan:
+			wg.Done()
+			return
+		}
+	}
+}
+
+func (s *RemotelyControlledSampler) getSampler() Sampler {
+	s.Lock()
+	defer s.Unlock()
+	return s.sampler
+}
+
+func (s *RemotelyControlledSampler) setSampler(sampler Sampler) {
+	s.Lock()
+	defer s.Unlock()
+	s.sampler = sampler
+}
+
+func (s *RemotelyControlledSampler) updateSampler() {
+	res, err := s.manager.GetSamplingStrategy(s.serviceName)
+	if err != nil {
+		s.metrics.SamplerQueryFailure.Inc(1)
+		return
+	}
+	s.Lock()
+	defer s.Unlock()
+
+	s.metrics.SamplerRetrieved.Inc(1)
+	if strategies := res.GetOperationSampling(); strategies != nil {
+		s.updateAdaptiveSampler(strategies)
+	} else {
+		err = s.updateRateLimitingOrProbabilisticSampler(res)
+	}
+	if err != nil {
+		s.metrics.SamplerUpdateFailure.Inc(1)
+		s.logger.Infof("Unable to handle sampling strategy response %+v. Got error: %v", res, err)
+		return
+	}
+	s.metrics.SamplerUpdated.Inc(1)
+}
+
+// NB: this function should only be called while holding a Write lock
+func (s *RemotelyControlledSampler) updateAdaptiveSampler(strategies *sampling.PerOperationSamplingStrategies) {
+	if adaptiveSampler, ok := s.sampler.(*adaptiveSampler); ok {
+		adaptiveSampler.update(strategies)
+	} else {
+		s.sampler = newAdaptiveSampler(strategies, s.maxOperations)
+	}
+}
+
+// NB: this function should only be called while holding a Write lock
+func (s *RemotelyControlledSampler) updateRateLimitingOrProbabilisticSampler(res *sampling.SamplingStrategyResponse) error {
+	var newSampler Sampler
+	if probabilistic := res.GetProbabilisticSampling(); probabilistic != nil {
+		newSampler = newProbabilisticSampler(probabilistic.SamplingRate)
+	} else if rateLimiting := res.GetRateLimitingSampling(); rateLimiting != nil {
+		newSampler = NewRateLimitingSampler(float64(rateLimiting.MaxTracesPerSecond))
+	} else {
+		return fmt.Errorf("Unsupported sampling strategy type %v", res.GetStrategyType())
+	}
+	if !s.sampler.Equal(newSampler) {
+		s.sampler = newSampler
+	}
+	return nil
+}