diff --git a/vendor/github.com/uber/jaeger-client-go/span.go b/vendor/github.com/uber/jaeger-client-go/span.go
new file mode 100644
index 0000000..997cffd
--- /dev/null
+++ b/vendor/github.com/uber/jaeger-client-go/span.go
@@ -0,0 +1,503 @@
+// Copyright (c) 2017-2018 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 (
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/opentracing/opentracing-go/log"
+)
+
+// Span implements opentracing.Span
+type Span struct {
+	// referenceCounter used to increase the lifetime of
+	// the object before return it into the pool.
+	referenceCounter int32
+
+	sync.RWMutex
+
+	tracer *Tracer
+
+	// TODO: (breaking change) change to use a pointer
+	context SpanContext
+
+	// The name of the "operation" this span is an instance of.
+	// Known as a "span name" in some implementations.
+	operationName string
+
+	// firstInProcess, if true, indicates that this span is the root of the (sub)tree
+	// of spans in the current process. In other words it's true for the root spans,
+	// and the ingress spans when the process joins another trace.
+	firstInProcess bool
+
+	// startTime is the timestamp indicating when the span began, with microseconds precision.
+	startTime time.Time
+
+	// duration returns duration of the span with microseconds precision.
+	// Zero value means duration is unknown.
+	duration time.Duration
+
+	// tags attached to this span
+	tags []Tag
+
+	// The span's "micro-log"
+	logs []opentracing.LogRecord
+
+	// The number of logs dropped because of MaxLogsPerSpan.
+	numDroppedLogs int
+
+	// references for this span
+	references []Reference
+
+	observer ContribSpanObserver
+}
+
+// Tag is a simple key value wrapper.
+// TODO (breaking change) deprecate in the next major release, use opentracing.Tag instead.
+type Tag struct {
+	key   string
+	value interface{}
+}
+
+// NewTag creates a new Tag.
+// TODO (breaking change) deprecate in the next major release, use opentracing.Tag instead.
+func NewTag(key string, value interface{}) Tag {
+	return Tag{key: key, value: value}
+}
+
+// SetOperationName sets or changes the operation name.
+func (s *Span) SetOperationName(operationName string) opentracing.Span {
+	s.Lock()
+	s.operationName = operationName
+	ctx := s.context
+	s.Unlock()
+	if !ctx.isSamplingFinalized() {
+		decision := s.tracer.sampler.OnSetOperationName(s, operationName)
+		s.applySamplingDecision(decision, true)
+	}
+	s.observer.OnSetOperationName(operationName)
+	return s
+}
+
+// SetTag implements SetTag() of opentracing.Span
+func (s *Span) SetTag(key string, value interface{}) opentracing.Span {
+	return s.setTagInternal(key, value, true)
+}
+
+func (s *Span) setTagInternal(key string, value interface{}, lock bool) opentracing.Span {
+	var ctx SpanContext
+	var operationName string
+	if lock {
+		ctx = s.SpanContext()
+		operationName = s.OperationName()
+	} else {
+		ctx = s.context
+		operationName = s.operationName
+	}
+
+	s.observer.OnSetTag(key, value)
+	if key == string(ext.SamplingPriority) && !setSamplingPriority(ctx.samplingState, operationName, s.tracer, value) {
+		return s
+	}
+	if !ctx.isSamplingFinalized() {
+		decision := s.tracer.sampler.OnSetTag(s, key, value)
+		s.applySamplingDecision(decision, lock)
+	}
+	if ctx.isWriteable() {
+		if lock {
+			s.Lock()
+			defer s.Unlock()
+		}
+		s.appendTagNoLocking(key, value)
+	}
+	return s
+}
+
+// SpanContext returns span context
+func (s *Span) SpanContext() SpanContext {
+	s.Lock()
+	defer s.Unlock()
+	return s.context
+}
+
+// StartTime returns span start time
+func (s *Span) StartTime() time.Time {
+	s.Lock()
+	defer s.Unlock()
+	return s.startTime
+}
+
+// Duration returns span duration
+func (s *Span) Duration() time.Duration {
+	s.Lock()
+	defer s.Unlock()
+	return s.duration
+}
+
+// Tags returns tags for span
+func (s *Span) Tags() opentracing.Tags {
+	s.Lock()
+	defer s.Unlock()
+	var result = make(opentracing.Tags, len(s.tags))
+	for _, tag := range s.tags {
+		result[tag.key] = tag.value
+	}
+	return result
+}
+
+// Logs returns micro logs for span
+func (s *Span) Logs() []opentracing.LogRecord {
+	s.Lock()
+	defer s.Unlock()
+
+	logs := append([]opentracing.LogRecord(nil), s.logs...)
+	if s.numDroppedLogs != 0 {
+		fixLogs(logs, s.numDroppedLogs)
+	}
+
+	return logs
+}
+
+// References returns references for this span
+func (s *Span) References() []opentracing.SpanReference {
+	s.Lock()
+	defer s.Unlock()
+
+	if s.references == nil || len(s.references) == 0 {
+		return nil
+	}
+
+	result := make([]opentracing.SpanReference, len(s.references))
+	for i, r := range s.references {
+		result[i] = opentracing.SpanReference{Type: r.Type, ReferencedContext: r.Context}
+	}
+	return result
+}
+
+func (s *Span) appendTagNoLocking(key string, value interface{}) {
+	s.tags = append(s.tags, Tag{key: key, value: value})
+}
+
+// LogFields implements opentracing.Span API
+func (s *Span) LogFields(fields ...log.Field) {
+	s.Lock()
+	defer s.Unlock()
+	if !s.context.IsSampled() {
+		return
+	}
+	s.logFieldsNoLocking(fields...)
+}
+
+// this function should only be called while holding a Write lock
+func (s *Span) logFieldsNoLocking(fields ...log.Field) {
+	lr := opentracing.LogRecord{
+		Fields:    fields,
+		Timestamp: time.Now(),
+	}
+	s.appendLogNoLocking(lr)
+}
+
+// LogKV implements opentracing.Span API
+func (s *Span) LogKV(alternatingKeyValues ...interface{}) {
+	s.RLock()
+	sampled := s.context.IsSampled()
+	s.RUnlock()
+	if !sampled {
+		return
+	}
+	fields, err := log.InterleavedKVToFields(alternatingKeyValues...)
+	if err != nil {
+		s.LogFields(log.Error(err), log.String("function", "LogKV"))
+		return
+	}
+	s.LogFields(fields...)
+}
+
+// LogEvent implements opentracing.Span API
+func (s *Span) LogEvent(event string) {
+	s.Log(opentracing.LogData{Event: event})
+}
+
+// LogEventWithPayload implements opentracing.Span API
+func (s *Span) LogEventWithPayload(event string, payload interface{}) {
+	s.Log(opentracing.LogData{Event: event, Payload: payload})
+}
+
+// Log implements opentracing.Span API
+func (s *Span) Log(ld opentracing.LogData) {
+	s.Lock()
+	defer s.Unlock()
+	if s.context.IsSampled() {
+		if ld.Timestamp.IsZero() {
+			ld.Timestamp = s.tracer.timeNow()
+		}
+		s.appendLogNoLocking(ld.ToLogRecord())
+	}
+}
+
+// this function should only be called while holding a Write lock
+func (s *Span) appendLogNoLocking(lr opentracing.LogRecord) {
+	maxLogs := s.tracer.options.maxLogsPerSpan
+	if maxLogs == 0 || len(s.logs) < maxLogs {
+		s.logs = append(s.logs, lr)
+		return
+	}
+
+	// We have too many logs. We don't touch the first numOld logs; we treat the
+	// rest as a circular buffer and overwrite the oldest log among those.
+	numOld := (maxLogs - 1) / 2
+	numNew := maxLogs - numOld
+	s.logs[numOld+s.numDroppedLogs%numNew] = lr
+	s.numDroppedLogs++
+}
+
+// rotateLogBuffer rotates the records in the buffer: records 0 to pos-1 move at
+// the end (i.e. pos circular left shifts).
+func rotateLogBuffer(buf []opentracing.LogRecord, pos int) {
+	// This algorithm is described in:
+	//    http://www.cplusplus.com/reference/algorithm/rotate
+	for first, middle, next := 0, pos, pos; first != middle; {
+		buf[first], buf[next] = buf[next], buf[first]
+		first++
+		next++
+		if next == len(buf) {
+			next = middle
+		} else if first == middle {
+			middle = next
+		}
+	}
+}
+
+func fixLogs(logs []opentracing.LogRecord, numDroppedLogs int) {
+	// We dropped some log events, which means that we used part of Logs as a
+	// circular buffer (see appendLog). De-circularize it.
+	numOld := (len(logs) - 1) / 2
+	numNew := len(logs) - numOld
+	rotateLogBuffer(logs[numOld:], numDroppedLogs%numNew)
+
+	// Replace the log in the middle (the oldest "new" log) with information
+	// about the dropped logs. This means that we are effectively dropping one
+	// more "new" log.
+	numDropped := numDroppedLogs + 1
+	logs[numOld] = opentracing.LogRecord{
+		// Keep the timestamp of the last dropped event.
+		Timestamp: logs[numOld].Timestamp,
+		Fields: []log.Field{
+			log.String("event", "dropped Span logs"),
+			log.Int("dropped_log_count", numDropped),
+			log.String("component", "jaeger-client"),
+		},
+	}
+}
+
+func (s *Span) fixLogsIfDropped() {
+	if s.numDroppedLogs == 0 {
+		return
+	}
+	fixLogs(s.logs, s.numDroppedLogs)
+	s.numDroppedLogs = 0
+}
+
+// SetBaggageItem implements SetBaggageItem() of opentracing.SpanContext.
+// The call is proxied via tracer.baggageSetter to allow policies to be applied
+// before allowing to set/replace baggage keys.
+// The setter eventually stores a new SpanContext with extended baggage:
+//
+//     span.context = span.context.WithBaggageItem(key, value)
+//
+//  See SpanContext.WithBaggageItem() for explanation why it's done this way.
+func (s *Span) SetBaggageItem(key, value string) opentracing.Span {
+	s.Lock()
+	defer s.Unlock()
+	s.tracer.setBaggage(s, key, value)
+	return s
+}
+
+// BaggageItem implements BaggageItem() of opentracing.SpanContext
+func (s *Span) BaggageItem(key string) string {
+	s.RLock()
+	defer s.RUnlock()
+	return s.context.baggage[key]
+}
+
+// Finish implements opentracing.Span API
+// After finishing the Span object it returns back to the allocator unless the reporter retains it again,
+// so after that, the Span object should no longer be used because it won't be valid anymore.
+func (s *Span) Finish() {
+	s.FinishWithOptions(opentracing.FinishOptions{})
+}
+
+// FinishWithOptions implements opentracing.Span API
+func (s *Span) FinishWithOptions(options opentracing.FinishOptions) {
+	if options.FinishTime.IsZero() {
+		options.FinishTime = s.tracer.timeNow()
+	}
+	s.observer.OnFinish(options)
+	s.Lock()
+	s.duration = options.FinishTime.Sub(s.startTime)
+	ctx := s.context
+	s.Unlock()
+	if !ctx.isSamplingFinalized() {
+		decision := s.tracer.sampler.OnFinishSpan(s)
+		s.applySamplingDecision(decision, true)
+	}
+	if ctx.IsSampled() {
+		s.Lock()
+		s.fixLogsIfDropped()
+		if len(options.LogRecords) > 0 || len(options.BulkLogData) > 0 {
+			// Note: bulk logs are not subject to maxLogsPerSpan limit
+			if options.LogRecords != nil {
+				s.logs = append(s.logs, options.LogRecords...)
+			}
+			for _, ld := range options.BulkLogData {
+				s.logs = append(s.logs, ld.ToLogRecord())
+			}
+		}
+		s.Unlock()
+	}
+	// call reportSpan even for non-sampled traces, to return span to the pool
+	// and update metrics counter
+	s.tracer.reportSpan(s)
+}
+
+// Context implements opentracing.Span API
+func (s *Span) Context() opentracing.SpanContext {
+	s.Lock()
+	defer s.Unlock()
+	return s.context
+}
+
+// Tracer implements opentracing.Span API
+func (s *Span) Tracer() opentracing.Tracer {
+	return s.tracer
+}
+
+func (s *Span) String() string {
+	s.RLock()
+	defer s.RUnlock()
+	return s.context.String()
+}
+
+// OperationName allows retrieving current operation name.
+func (s *Span) OperationName() string {
+	s.RLock()
+	defer s.RUnlock()
+	return s.operationName
+}
+
+// Retain increases object counter to increase the lifetime of the object
+func (s *Span) Retain() *Span {
+	atomic.AddInt32(&s.referenceCounter, 1)
+	return s
+}
+
+// Release decrements object counter and return to the
+// allocator manager  when counter will below zero
+func (s *Span) Release() {
+	if atomic.AddInt32(&s.referenceCounter, -1) == -1 {
+		s.tracer.spanAllocator.Put(s)
+	}
+}
+
+// reset span state and release unused data
+func (s *Span) reset() {
+	s.firstInProcess = false
+	s.context = emptyContext
+	s.operationName = ""
+	s.tracer = nil
+	s.startTime = time.Time{}
+	s.duration = 0
+	s.observer = nil
+	atomic.StoreInt32(&s.referenceCounter, 0)
+
+	// Note: To reuse memory we can save the pointers on the heap
+	s.tags = s.tags[:0]
+	s.logs = s.logs[:0]
+	s.numDroppedLogs = 0
+	s.references = s.references[:0]
+}
+
+func (s *Span) serviceName() string {
+	return s.tracer.serviceName
+}
+
+func (s *Span) applySamplingDecision(decision SamplingDecision, lock bool) {
+	var ctx SpanContext
+	if lock {
+		ctx = s.SpanContext()
+	} else {
+		ctx = s.context
+	}
+
+	if !decision.Retryable {
+		ctx.samplingState.setFinal()
+	}
+	if decision.Sample {
+		ctx.samplingState.setSampled()
+		if len(decision.Tags) > 0 {
+			if lock {
+				s.Lock()
+				defer s.Unlock()
+			}
+			for _, tag := range decision.Tags {
+				s.appendTagNoLocking(tag.key, tag.value)
+			}
+		}
+	}
+}
+
+// setSamplingPriority returns true if the flag was updated successfully, false otherwise.
+// The behavior of setSamplingPriority is surprising
+// If noDebugFlagOnForcedSampling is set
+//     setSamplingPriority(..., 1) always sets only flagSampled
+// If noDebugFlagOnForcedSampling is unset, and isDebugAllowed passes
+//     setSamplingPriority(..., 1) sets both flagSampled and flagDebug
+// However,
+//     setSamplingPriority(..., 0) always only resets flagSampled
+//
+// This means that doing a setSamplingPriority(..., 1) followed by setSamplingPriority(..., 0) can
+// leave flagDebug set
+func setSamplingPriority(state *samplingState, operationName string, tracer *Tracer, value interface{}) bool {
+	val, ok := value.(uint16)
+	if !ok {
+		return false
+	}
+	if val == 0 {
+		state.unsetSampled()
+		state.setFinal()
+		return true
+	}
+	if tracer.options.noDebugFlagOnForcedSampling {
+		state.setSampled()
+		state.setFinal()
+		return true
+	} else if tracer.isDebugAllowed(operationName) {
+		state.setDebugAndSampled()
+		state.setFinal()
+		return true
+	}
+	return false
+}
+
+// EnableFirehose enables firehose flag on the span context
+func EnableFirehose(s *Span) {
+	s.Lock()
+	defer s.Unlock()
+	s.context.samplingState.setFirehose()
+}