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 0000000..d0be8ad
--- /dev/null
+++ b/vendor/github.com/uber/jaeger-client-go/sampler.go
@@ -0,0 +1,516 @@
+// 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
+}