Bump github.com/uber/jaeger-client-go

Bumps [github.com/uber/jaeger-client-go](https://github.com/uber/jaeger-client-go) from 2.19.0+incompatible to 2.20.0+incompatible.
- [Release notes](https://github.com/uber/jaeger-client-go/releases)
- [Changelog](https://github.com/jaegertracing/jaeger-client-go/blob/master/CHANGELOG.md)
- [Commits](https://github.com/uber/jaeger-client-go/compare/v2.19.0...v2.20.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

vendor/github.com/uber/jaeger-client-go/sampler_remote.go

@@ -0,0 +1,334 @@
+// 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/thrift-gen/sampling"
+)
+
+const (
+	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
+	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 {
+	return s.sampler.OnCreateSpan(span)
+}
+
+// OnSetOperationName implements OnSetOperationName of SamplerV2.
+func (s *RemotelyControlledSampler) OnSetOperationName(span *Span, operationName string) SamplingDecision {
+	return s.sampler.OnSetOperationName(span, operationName)
+}
+
+// OnSetTag implements OnSetTag of SamplerV2.
+func (s *RemotelyControlledSampler) OnSetTag(span *Span, key string, value interface{}) SamplingDecision {
+	return s.sampler.OnSetTag(span, key, value)
+}
+
+// OnFinishSpan implements OnFinishSpan of SamplerV2.
+func (s *RemotelyControlledSampler) OnFinishSpan(span *Span) SamplingDecision {
+	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.Lock()
+	defer s.Unlock()
+	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.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.
+type AdaptiveSamplerUpdater struct {
+	MaxOperations            int // required
+	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    Logger
+}
+
+func (f *httpSamplingStrategyFetcher) Fetch(serviceName string) ([]byte, error) {
+	v := url.Values{}
+	v.Set("service", serviceName)
+	uri := f.serverURL + "?" + v.Encode()
+
+	// TODO create and reuse http.Client with proper timeout settings, etc.
+	resp, err := http.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
+}