vendor/github.com/uber/jaeger-client-go/sampler_remote.go - voltha-openonu-adapter-go - Gitiles

 // 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 (
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
 	"net/http"
 	"net/url"
 	"sync"
 	"sync/atomic"
 	"time"

 	"github.com/uber/jaeger-client-go/log"
 	"github.com/uber/jaeger-client-go/thrift-gen/sampling"
 )

 const (
 	defaultRemoteSamplingTimeout   = 10 * time.Second
 	defaultSamplingRefreshInterval = time.Minute
 )

 // SamplingStrategyFetcher is used to fetch sampling strategy updates from remote server.
 type SamplingStrategyFetcher interface {
 	Fetch(service string) ([]byte, error)
 }

 // SamplingStrategyParser is used to parse sampling strategy updates. The output object
 // should be of the type that is recognized by the SamplerUpdaters.
 type SamplingStrategyParser interface {
 	Parse(response []byte) (interface{}, error)
 }

 // SamplerUpdater is used by RemotelyControlledSampler to apply sampling strategies,
 // retrieved from remote config server, to the current sampler. The updater can modify
 // the sampler in-place if sampler supports it, or create a new one.
 //
 // If the strategy does not contain configuration for the sampler in question,
 // updater must return modifiedSampler=nil to give other updaters a chance to inspect
 // the sampling strategy response.
 //
 // RemotelyControlledSampler invokes the updaters while holding a lock on the main sampler.
 type SamplerUpdater interface {
 	Update(sampler SamplerV2, strategy interface{}) (modified SamplerV2, err error)
 }

 // 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 // used to serialize access to samplerOptions.sampler
 	samplerOptions

 	serviceName string
 	doneChan    chan *sync.WaitGroup
 }

 // 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 := new(samplerOptions).applyOptionsAndDefaults(opts...)
 	sampler := &RemotelyControlledSampler{
 		samplerOptions: *options,
 		serviceName:    serviceName,
 		doneChan:       make(chan *sync.WaitGroup),
 	}
 	go sampler.pollController()
 	return sampler
 }

 // IsSampled implements IsSampled() of Sampler.
 // TODO (breaking change) remove when Sampler V1 is removed
 func (s *RemotelyControlledSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
 	return false, nil
 }

 // OnCreateSpan implements OnCreateSpan of SamplerV2.
 func (s *RemotelyControlledSampler) OnCreateSpan(span *Span) SamplingDecision {
 	s.RLock()
 	defer s.RUnlock()
 	return s.sampler.OnCreateSpan(span)
 }

 // OnSetOperationName implements OnSetOperationName of SamplerV2.
 func (s *RemotelyControlledSampler) OnSetOperationName(span *Span, operationName string) SamplingDecision {
 	s.RLock()
 	defer s.RUnlock()
 	return s.sampler.OnSetOperationName(span, operationName)
 }

 // OnSetTag implements OnSetTag of SamplerV2.
 func (s *RemotelyControlledSampler) OnSetTag(span *Span, key string, value interface{}) SamplingDecision {
 	s.RLock()
 	defer s.RUnlock()
 	return s.sampler.OnSetTag(span, key, value)
 }

 // OnFinishSpan implements OnFinishSpan of SamplerV2.
 func (s *RemotelyControlledSampler) OnFinishSpan(span *Span) SamplingDecision {
 	s.RLock()
 	defer s.RUnlock()
 	return s.sampler.OnFinishSpan(span)
 }

 // 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 PerOperationSampler.Equal() for
 	// more information.
 	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
 		}
 	}
 }

 // Sampler returns the currently active sampler.
 func (s *RemotelyControlledSampler) Sampler() SamplerV2 {
 	s.RLock()
 	defer s.RUnlock()
 	return s.sampler
 }
 func (s *RemotelyControlledSampler) setSampler(sampler SamplerV2) {
 	s.Lock()
 	defer s.Unlock()
 	s.sampler = sampler
 }

 // UpdateSampler forces the sampler to fetch sampling strategy from backend server.
 // This function is called automatically on a timer, but can also be safely called manually, e.g. from tests.
 func (s *RemotelyControlledSampler) UpdateSampler() {
 	res, err := s.samplingFetcher.Fetch(s.serviceName)
 	if err != nil {
 		s.metrics.SamplerQueryFailure.Inc(1)
 		s.logger.Infof("failed to fetch sampling strategy: %v", err)
 		return
 	}
 	strategy, err := s.samplingParser.Parse(res)
 	if err != nil {
 		s.metrics.SamplerUpdateFailure.Inc(1)
 		s.logger.Infof("failed to parse sampling strategy response: %v", err)
 		return
 	}

 	s.Lock()
 	defer s.Unlock()

 	s.metrics.SamplerRetrieved.Inc(1)
 	if err := s.updateSamplerViaUpdaters(strategy); err != nil {
 		s.metrics.SamplerUpdateFailure.Inc(1)
 		s.logger.Infof("failed 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) updateSamplerViaUpdaters(strategy interface{}) error {
 	for _, updater := range s.updaters {
 		sampler, err := updater.Update(s.sampler, strategy)
 		if err != nil {
 			return err
 		}
 		if sampler != nil {
 			s.logger.Debugf("sampler updated: %+v", sampler)
 			s.sampler = sampler
 			return nil
 		}
 	}
 	return fmt.Errorf("unsupported sampling strategy %+v", strategy)
 }

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

 // ProbabilisticSamplerUpdater is used by RemotelyControlledSampler to parse sampling configuration.
 type ProbabilisticSamplerUpdater struct{}

 // Update implements Update of SamplerUpdater.
 func (u *ProbabilisticSamplerUpdater) Update(sampler SamplerV2, strategy interface{}) (SamplerV2, error) {
 	type response interface {
 		GetProbabilisticSampling() *sampling.ProbabilisticSamplingStrategy
 	}
 	var _ response = new(sampling.SamplingStrategyResponse) // sanity signature check
 	if resp, ok := strategy.(response); ok {
 		if probabilistic := resp.GetProbabilisticSampling(); probabilistic != nil {
 			if ps, ok := sampler.(*ProbabilisticSampler); ok {
 				if err := ps.Update(probabilistic.SamplingRate); err != nil {
 					return nil, err
 				}
 				return sampler, nil
 			}
 			return newProbabilisticSampler(probabilistic.SamplingRate), nil
 		}
 	}
 	return nil, nil
 }

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

 // RateLimitingSamplerUpdater is used by RemotelyControlledSampler to parse sampling configuration.
 type RateLimitingSamplerUpdater struct{}

 // Update implements Update of SamplerUpdater.
 func (u *RateLimitingSamplerUpdater) Update(sampler SamplerV2, strategy interface{}) (SamplerV2, error) {
 	type response interface {
 		GetRateLimitingSampling() *sampling.RateLimitingSamplingStrategy
 	}
 	var _ response = new(sampling.SamplingStrategyResponse) // sanity signature check
 	if resp, ok := strategy.(response); ok {
 		if rateLimiting := resp.GetRateLimitingSampling(); rateLimiting != nil {
 			rateLimit := float64(rateLimiting.MaxTracesPerSecond)
 			if rl, ok := sampler.(*RateLimitingSampler); ok {
 				rl.Update(rateLimit)
 				return rl, nil
 			}
 			return NewRateLimitingSampler(rateLimit), nil
 		}
 	}
 	return nil, nil
 }

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

 // AdaptiveSamplerUpdater is used by RemotelyControlledSampler to parse sampling configuration.
 // Fields have the same meaning as in PerOperationSamplerParams.
 type AdaptiveSamplerUpdater struct {
 	MaxOperations            int
 	OperationNameLateBinding bool
 }

 // Update implements Update of SamplerUpdater.
 func (u *AdaptiveSamplerUpdater) Update(sampler SamplerV2, strategy interface{}) (SamplerV2, error) {
 	type response interface {
 		GetOperationSampling() *sampling.PerOperationSamplingStrategies
 	}
 	var _ response = new(sampling.SamplingStrategyResponse) // sanity signature check
 	if p, ok := strategy.(response); ok {
 		if operations := p.GetOperationSampling(); operations != nil {
 			if as, ok := sampler.(*PerOperationSampler); ok {
 				as.update(operations)
 				return as, nil
 			}
 			return NewPerOperationSampler(PerOperationSamplerParams{
 				MaxOperations:            u.MaxOperations,
 				OperationNameLateBinding: u.OperationNameLateBinding,
 				Strategies:               operations,
 			}), nil
 		}
 	}
 	return nil, nil
 }

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

 type httpSamplingStrategyFetcher struct {
 	serverURL  string
 	logger     log.DebugLogger
 	httpClient http.Client
 }

 func newHTTPSamplingStrategyFetcher(serverURL string, logger log.DebugLogger) *httpSamplingStrategyFetcher {
 	customTransport := http.DefaultTransport.(*http.Transport).Clone()
 	customTransport.ResponseHeaderTimeout = defaultRemoteSamplingTimeout

 	return &httpSamplingStrategyFetcher{
 		serverURL: serverURL,
 		logger:    logger,
 		httpClient: http.Client{
 			Transport: customTransport,
 		},
 	}
 }

 func (f *httpSamplingStrategyFetcher) Fetch(serviceName string) ([]byte, error) {
 	v := url.Values{}
 	v.Set("service", serviceName)
 	uri := f.serverURL + "?" + v.Encode()

 	resp, err := f.httpClient.Get(uri)
 	if err != nil {
 		return nil, err
 	}

 	defer func() {
 		if err := resp.Body.Close(); err != nil {
 			f.logger.Error(fmt.Sprintf("failed to close HTTP response body: %+v", err))
 		}
 	}()

 	body, err := ioutil.ReadAll(resp.Body)
 	if err != nil {
 		return nil, err
 	}

 	if resp.StatusCode >= 400 {
 		return nil, fmt.Errorf("StatusCode: %d, Body: %s", resp.StatusCode, body)
 	}

 	return body, nil
 }

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

 type samplingStrategyParser struct{}

 func (p *samplingStrategyParser) Parse(response []byte) (interface{}, error) {
 	strategy := new(sampling.SamplingStrategyResponse)
 	if err := json.Unmarshal(response, strategy); err != nil {
 		return nil, err
 	}
 	return strategy, nil
 }
	// 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 (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"sync"
	"sync/atomic"
	"time"

	"github.com/uber/jaeger-client-go/log"
	"github.com/uber/jaeger-client-go/thrift-gen/sampling"
	)

	const (
	defaultRemoteSamplingTimeout = 10 * time.Second
	defaultSamplingRefreshInterval = time.Minute
	)

	// SamplingStrategyFetcher is used to fetch sampling strategy updates from remote server.
	type SamplingStrategyFetcher interface {
	Fetch(service string) ([]byte, error)
	}

	// SamplingStrategyParser is used to parse sampling strategy updates. The output object
	// should be of the type that is recognized by the SamplerUpdaters.
	type SamplingStrategyParser interface {
	Parse(response []byte) (interface{}, error)
	}

	// SamplerUpdater is used by RemotelyControlledSampler to apply sampling strategies,
	// retrieved from remote config server, to the current sampler. The updater can modify
	// the sampler in-place if sampler supports it, or create a new one.
	//
	// If the strategy does not contain configuration for the sampler in question,
	// updater must return modifiedSampler=nil to give other updaters a chance to inspect
	// the sampling strategy response.
	//
	// RemotelyControlledSampler invokes the updaters while holding a lock on the main sampler.
	type SamplerUpdater interface {
	Update(sampler SamplerV2, strategy interface{}) (modified SamplerV2, err error)
	}

	// 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 // used to serialize access to samplerOptions.sampler
	samplerOptions

	serviceName string
	doneChan chan *sync.WaitGroup
	}

	// 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 := new(samplerOptions).applyOptionsAndDefaults(opts...)
	sampler := &RemotelyControlledSampler{
	samplerOptions: *options,
	serviceName: serviceName,
	doneChan: make(chan *sync.WaitGroup),
	}
	go sampler.pollController()
	return sampler
	}

	// IsSampled implements IsSampled() of Sampler.
	// TODO (breaking change) remove when Sampler V1 is removed
	func (s *RemotelyControlledSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
	return false, nil
	}

	// OnCreateSpan implements OnCreateSpan of SamplerV2.
	func (s RemotelyControlledSampler) OnCreateSpan(span Span) SamplingDecision {
	s.RLock()
	defer s.RUnlock()
	return s.sampler.OnCreateSpan(span)
	}

	// OnSetOperationName implements OnSetOperationName of SamplerV2.
	func (s RemotelyControlledSampler) OnSetOperationName(span Span, operationName string) SamplingDecision {
	s.RLock()
	defer s.RUnlock()
	return s.sampler.OnSetOperationName(span, operationName)
	}

	// OnSetTag implements OnSetTag of SamplerV2.
	func (s RemotelyControlledSampler) OnSetTag(span Span, key string, value interface{}) SamplingDecision {
	s.RLock()
	defer s.RUnlock()
	return s.sampler.OnSetTag(span, key, value)
	}

	// OnFinishSpan implements OnFinishSpan of SamplerV2.
	func (s RemotelyControlledSampler) OnFinishSpan(span Span) SamplingDecision {
	s.RLock()
	defer s.RUnlock()
	return s.sampler.OnFinishSpan(span)
	}

	// 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 PerOperationSampler.Equal() for
	// more information.
	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
	}
	}
	}

	// Sampler returns the currently active sampler.
	func (s *RemotelyControlledSampler) Sampler() SamplerV2 {
	s.RLock()
	defer s.RUnlock()
	return s.sampler
	}
	func (s *RemotelyControlledSampler) setSampler(sampler SamplerV2) {
	s.Lock()
	defer s.Unlock()
	s.sampler = sampler
	}

	// UpdateSampler forces the sampler to fetch sampling strategy from backend server.
	// This function is called automatically on a timer, but can also be safely called manually, e.g. from tests.
	func (s *RemotelyControlledSampler) UpdateSampler() {
	res, err := s.samplingFetcher.Fetch(s.serviceName)
	if err != nil {
	s.metrics.SamplerQueryFailure.Inc(1)
	s.logger.Infof("failed to fetch sampling strategy: %v", err)
	return
	}
	strategy, err := s.samplingParser.Parse(res)
	if err != nil {
	s.metrics.SamplerUpdateFailure.Inc(1)
	s.logger.Infof("failed to parse sampling strategy response: %v", err)
	return
	}

	s.Lock()
	defer s.Unlock()

	s.metrics.SamplerRetrieved.Inc(1)
	if err := s.updateSamplerViaUpdaters(strategy); err != nil {
	s.metrics.SamplerUpdateFailure.Inc(1)
	s.logger.Infof("failed 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) updateSamplerViaUpdaters(strategy interface{}) error {
	for _, updater := range s.updaters {
	sampler, err := updater.Update(s.sampler, strategy)
	if err != nil {
	return err
	}
	if sampler != nil {
	s.logger.Debugf("sampler updated: %+v", sampler)
	s.sampler = sampler
	return nil
	}
	}
	return fmt.Errorf("unsupported sampling strategy %+v", strategy)
	}

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

	// ProbabilisticSamplerUpdater is used by RemotelyControlledSampler to parse sampling configuration.
	type ProbabilisticSamplerUpdater struct{}

	// Update implements Update of SamplerUpdater.
	func (u *ProbabilisticSamplerUpdater) Update(sampler SamplerV2, strategy interface{}) (SamplerV2, error) {
	type response interface {
	GetProbabilisticSampling() *sampling.ProbabilisticSamplingStrategy
	}
	var _ response = new(sampling.SamplingStrategyResponse) // sanity signature check
	if resp, ok := strategy.(response); ok {
	if probabilistic := resp.GetProbabilisticSampling(); probabilistic != nil {
	if ps, ok := sampler.(*ProbabilisticSampler); ok {
	if err := ps.Update(probabilistic.SamplingRate); err != nil {
	return nil, err
	}
	return sampler, nil
	}
	return newProbabilisticSampler(probabilistic.SamplingRate), nil
	}
	}
	return nil, nil
	}

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

	// RateLimitingSamplerUpdater is used by RemotelyControlledSampler to parse sampling configuration.
	type RateLimitingSamplerUpdater struct{}

	// Update implements Update of SamplerUpdater.
	func (u *RateLimitingSamplerUpdater) Update(sampler SamplerV2, strategy interface{}) (SamplerV2, error) {
	type response interface {
	GetRateLimitingSampling() *sampling.RateLimitingSamplingStrategy
	}
	var _ response = new(sampling.SamplingStrategyResponse) // sanity signature check
	if resp, ok := strategy.(response); ok {
	if rateLimiting := resp.GetRateLimitingSampling(); rateLimiting != nil {
	rateLimit := float64(rateLimiting.MaxTracesPerSecond)
	if rl, ok := sampler.(*RateLimitingSampler); ok {
	rl.Update(rateLimit)
	return rl, nil
	}
	return NewRateLimitingSampler(rateLimit), nil
	}
	}
	return nil, nil
	}

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

	// AdaptiveSamplerUpdater is used by RemotelyControlledSampler to parse sampling configuration.
	// Fields have the same meaning as in PerOperationSamplerParams.
	type AdaptiveSamplerUpdater struct {
	MaxOperations int
	OperationNameLateBinding bool
	}

	// Update implements Update of SamplerUpdater.
	func (u *AdaptiveSamplerUpdater) Update(sampler SamplerV2, strategy interface{}) (SamplerV2, error) {
	type response interface {
	GetOperationSampling() *sampling.PerOperationSamplingStrategies
	}
	var _ response = new(sampling.SamplingStrategyResponse) // sanity signature check
	if p, ok := strategy.(response); ok {
	if operations := p.GetOperationSampling(); operations != nil {
	if as, ok := sampler.(*PerOperationSampler); ok {
	as.update(operations)
	return as, nil
	}
	return NewPerOperationSampler(PerOperationSamplerParams{
	MaxOperations: u.MaxOperations,
	OperationNameLateBinding: u.OperationNameLateBinding,
	Strategies: operations,
	}), nil
	}
	}
	return nil, nil
	}

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

	type httpSamplingStrategyFetcher struct {
	serverURL string
	logger log.DebugLogger
	httpClient http.Client
	}

	func newHTTPSamplingStrategyFetcher(serverURL string, logger log.DebugLogger) *httpSamplingStrategyFetcher {
	customTransport := http.DefaultTransport.(*http.Transport).Clone()
	customTransport.ResponseHeaderTimeout = defaultRemoteSamplingTimeout

	return &httpSamplingStrategyFetcher{
	serverURL: serverURL,
	logger: logger,
	httpClient: http.Client{
	Transport: customTransport,
	},
	}
	}

	func (f *httpSamplingStrategyFetcher) Fetch(serviceName string) ([]byte, error) {
	v := url.Values{}
	v.Set("service", serviceName)
	uri := f.serverURL + "?" + v.Encode()

	resp, err := f.httpClient.Get(uri)
	if err != nil {
	return nil, err
	}

	defer func() {
	if err := resp.Body.Close(); err != nil {
	f.logger.Error(fmt.Sprintf("failed to close HTTP response body: %+v", err))
	}
	}()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
	return nil, err
	}

	if resp.StatusCode >= 400 {
	return nil, fmt.Errorf("StatusCode: %d, Body: %s", resp.StatusCode, body)
	}

	return body, nil
	}

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

	type samplingStrategyParser struct{}

	func (p *samplingStrategyParser) Parse(response []byte) (interface{}, error) {
	strategy := new(sampling.SamplingStrategyResponse)
	if err := json.Unmarshal(response, strategy); err != nil {
	return nil, err
	}
	return strategy, nil
	}