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Move remote sampler to its own files #448

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Oct 15, 2019
Merged

Move remote sampler to its own files #448

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fdc8c87
Move remote sampler to its own files
Oct 15, 2019
d548581
Fix lint error
Oct 15, 2019
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195 changes: 1 addition & 194 deletions sampler.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,19 +17,14 @@ 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 (
defaultSamplingRefreshInterval = time.Minute
defaultMaxOperations = 2000
defaultMaxOperations = 2000
)

// Sampler decides whether a new trace should be sampled or not.
Expand Down Expand Up @@ -375,191 +370,3 @@ func (s *adaptiveSampler) update(strategies *sampling.PerOperationSamplingStrate
}
s.samplers = newSamplers
}

// -----------------------

// 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)
s.logger.Infof("Unable to query sampling strategy: %v", err)
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
}
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