Initial

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

vendor/go.opencensus.io/trace/trace.go

@@ -0,0 +1,598 @@
+// Copyright 2017, OpenCensus Authors
+//
+// 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 trace
+
+import (
+	"context"
+	crand "crypto/rand"
+	"encoding/binary"
+	"fmt"
+	"math/rand"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"go.opencensus.io/internal"
+	"go.opencensus.io/trace/tracestate"
+)
+
+// Span represents a span of a trace.  It has an associated SpanContext, and
+// stores data accumulated while the span is active.
+//
+// Ideally users should interact with Spans by calling the functions in this
+// package that take a Context parameter.
+type Span struct {
+	// data contains information recorded about the span.
+	//
+	// It will be non-nil if we are exporting the span or recording events for it.
+	// Otherwise, data is nil, and the Span is simply a carrier for the
+	// SpanContext, so that the trace ID is propagated.
+	data        *SpanData
+	mu          sync.Mutex // protects the contents of *data (but not the pointer value.)
+	spanContext SpanContext
+
+	// lruAttributes are capped at configured limit. When the capacity is reached an oldest entry
+	// is removed to create room for a new entry.
+	lruAttributes *lruMap
+
+	// annotations are stored in FIFO queue capped by configured limit.
+	annotations *evictedQueue
+
+	// messageEvents are stored in FIFO queue capped by configured limit.
+	messageEvents *evictedQueue
+
+	// links are stored in FIFO queue capped by configured limit.
+	links *evictedQueue
+
+	// spanStore is the spanStore this span belongs to, if any, otherwise it is nil.
+	*spanStore
+	endOnce sync.Once
+
+	executionTracerTaskEnd func() // ends the execution tracer span
+}
+
+// IsRecordingEvents returns true if events are being recorded for this span.
+// Use this check to avoid computing expensive annotations when they will never
+// be used.
+func (s *Span) IsRecordingEvents() bool {
+	if s == nil {
+		return false
+	}
+	return s.data != nil
+}
+
+// TraceOptions contains options associated with a trace span.
+type TraceOptions uint32
+
+// IsSampled returns true if the span will be exported.
+func (sc SpanContext) IsSampled() bool {
+	return sc.TraceOptions.IsSampled()
+}
+
+// setIsSampled sets the TraceOptions bit that determines whether the span will be exported.
+func (sc *SpanContext) setIsSampled(sampled bool) {
+	if sampled {
+		sc.TraceOptions |= 1
+	} else {
+		sc.TraceOptions &= ^TraceOptions(1)
+	}
+}
+
+// IsSampled returns true if the span will be exported.
+func (t TraceOptions) IsSampled() bool {
+	return t&1 == 1
+}
+
+// SpanContext contains the state that must propagate across process boundaries.
+//
+// SpanContext is not an implementation of context.Context.
+// TODO: add reference to external Census docs for SpanContext.
+type SpanContext struct {
+	TraceID      TraceID
+	SpanID       SpanID
+	TraceOptions TraceOptions
+	Tracestate   *tracestate.Tracestate
+}
+
+type contextKey struct{}
+
+// FromContext returns the Span stored in a context, or nil if there isn't one.
+func FromContext(ctx context.Context) *Span {
+	s, _ := ctx.Value(contextKey{}).(*Span)
+	return s
+}
+
+// NewContext returns a new context with the given Span attached.
+func NewContext(parent context.Context, s *Span) context.Context {
+	return context.WithValue(parent, contextKey{}, s)
+}
+
+// All available span kinds. Span kind must be either one of these values.
+const (
+	SpanKindUnspecified = iota
+	SpanKindServer
+	SpanKindClient
+)
+
+// StartOptions contains options concerning how a span is started.
+type StartOptions struct {
+	// Sampler to consult for this Span. If provided, it is always consulted.
+	//
+	// If not provided, then the behavior differs based on whether
+	// the parent of this Span is remote, local, or there is no parent.
+	// In the case of a remote parent or no parent, the
+	// default sampler (see Config) will be consulted. Otherwise,
+	// when there is a non-remote parent, no new sampling decision will be made:
+	// we will preserve the sampling of the parent.
+	Sampler Sampler
+
+	// SpanKind represents the kind of a span. If none is set,
+	// SpanKindUnspecified is used.
+	SpanKind int
+}
+
+// StartOption apply changes to StartOptions.
+type StartOption func(*StartOptions)
+
+// WithSpanKind makes new spans to be created with the given kind.
+func WithSpanKind(spanKind int) StartOption {
+	return func(o *StartOptions) {
+		o.SpanKind = spanKind
+	}
+}
+
+// WithSampler makes new spans to be be created with a custom sampler.
+// Otherwise, the global sampler is used.
+func WithSampler(sampler Sampler) StartOption {
+	return func(o *StartOptions) {
+		o.Sampler = sampler
+	}
+}
+
+// StartSpan starts a new child span of the current span in the context. If
+// there is no span in the context, creates a new trace and span.
+//
+// Returned context contains the newly created span. You can use it to
+// propagate the returned span in process.
+func StartSpan(ctx context.Context, name string, o ...StartOption) (context.Context, *Span) {
+	var opts StartOptions
+	var parent SpanContext
+	if p := FromContext(ctx); p != nil {
+		p.addChild()
+		parent = p.spanContext
+	}
+	for _, op := range o {
+		op(&opts)
+	}
+	span := startSpanInternal(name, parent != SpanContext{}, parent, false, opts)
+
+	ctx, end := startExecutionTracerTask(ctx, name)
+	span.executionTracerTaskEnd = end
+	return NewContext(ctx, span), span
+}
+
+// StartSpanWithRemoteParent starts a new child span of the span from the given parent.
+//
+// If the incoming context contains a parent, it ignores. StartSpanWithRemoteParent is
+// preferred for cases where the parent is propagated via an incoming request.
+//
+// Returned context contains the newly created span. You can use it to
+// propagate the returned span in process.
+func StartSpanWithRemoteParent(ctx context.Context, name string, parent SpanContext, o ...StartOption) (context.Context, *Span) {
+	var opts StartOptions
+	for _, op := range o {
+		op(&opts)
+	}
+	span := startSpanInternal(name, parent != SpanContext{}, parent, true, opts)
+	ctx, end := startExecutionTracerTask(ctx, name)
+	span.executionTracerTaskEnd = end
+	return NewContext(ctx, span), span
+}
+
+func startSpanInternal(name string, hasParent bool, parent SpanContext, remoteParent bool, o StartOptions) *Span {
+	span := &Span{}
+	span.spanContext = parent
+
+	cfg := config.Load().(*Config)
+
+	if !hasParent {
+		span.spanContext.TraceID = cfg.IDGenerator.NewTraceID()
+	}
+	span.spanContext.SpanID = cfg.IDGenerator.NewSpanID()
+	sampler := cfg.DefaultSampler
+
+	if !hasParent || remoteParent || o.Sampler != nil {
+		// If this span is the child of a local span and no Sampler is set in the
+		// options, keep the parent's TraceOptions.
+		//
+		// Otherwise, consult the Sampler in the options if it is non-nil, otherwise
+		// the default sampler.
+		if o.Sampler != nil {
+			sampler = o.Sampler
+		}
+		span.spanContext.setIsSampled(sampler(SamplingParameters{
+			ParentContext:   parent,
+			TraceID:         span.spanContext.TraceID,
+			SpanID:          span.spanContext.SpanID,
+			Name:            name,
+			HasRemoteParent: remoteParent}).Sample)
+	}
+
+	if !internal.LocalSpanStoreEnabled && !span.spanContext.IsSampled() {
+		return span
+	}
+
+	span.data = &SpanData{
+		SpanContext:     span.spanContext,
+		StartTime:       time.Now(),
+		SpanKind:        o.SpanKind,
+		Name:            name,
+		HasRemoteParent: remoteParent,
+	}
+	span.lruAttributes = newLruMap(cfg.MaxAttributesPerSpan)
+	span.annotations = newEvictedQueue(cfg.MaxAnnotationEventsPerSpan)
+	span.messageEvents = newEvictedQueue(cfg.MaxMessageEventsPerSpan)
+	span.links = newEvictedQueue(cfg.MaxLinksPerSpan)
+
+	if hasParent {
+		span.data.ParentSpanID = parent.SpanID
+	}
+	if internal.LocalSpanStoreEnabled {
+		var ss *spanStore
+		ss = spanStoreForNameCreateIfNew(name)
+		if ss != nil {
+			span.spanStore = ss
+			ss.add(span)
+		}
+	}
+
+	return span
+}
+
+// End ends the span.
+func (s *Span) End() {
+	if s == nil {
+		return
+	}
+	if s.executionTracerTaskEnd != nil {
+		s.executionTracerTaskEnd()
+	}
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.endOnce.Do(func() {
+		exp, _ := exporters.Load().(exportersMap)
+		mustExport := s.spanContext.IsSampled() && len(exp) > 0
+		if s.spanStore != nil || mustExport {
+			sd := s.makeSpanData()
+			sd.EndTime = internal.MonotonicEndTime(sd.StartTime)
+			if s.spanStore != nil {
+				s.spanStore.finished(s, sd)
+			}
+			if mustExport {
+				for e := range exp {
+					e.ExportSpan(sd)
+				}
+			}
+		}
+	})
+}
+
+// makeSpanData produces a SpanData representing the current state of the Span.
+// It requires that s.data is non-nil.
+func (s *Span) makeSpanData() *SpanData {
+	var sd SpanData
+	s.mu.Lock()
+	sd = *s.data
+	if s.lruAttributes.len() > 0 {
+		sd.Attributes = s.lruAttributesToAttributeMap()
+		sd.DroppedAttributeCount = s.lruAttributes.droppedCount
+	}
+	if len(s.annotations.queue) > 0 {
+		sd.Annotations = s.interfaceArrayToAnnotationArray()
+		sd.DroppedAnnotationCount = s.annotations.droppedCount
+	}
+	if len(s.messageEvents.queue) > 0 {
+		sd.MessageEvents = s.interfaceArrayToMessageEventArray()
+		sd.DroppedMessageEventCount = s.messageEvents.droppedCount
+	}
+	if len(s.links.queue) > 0 {
+		sd.Links = s.interfaceArrayToLinksArray()
+		sd.DroppedLinkCount = s.links.droppedCount
+	}
+	s.mu.Unlock()
+	return &sd
+}
+
+// SpanContext returns the SpanContext of the span.
+func (s *Span) SpanContext() SpanContext {
+	if s == nil {
+		return SpanContext{}
+	}
+	return s.spanContext
+}
+
+// SetName sets the name of the span, if it is recording events.
+func (s *Span) SetName(name string) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.mu.Lock()
+	s.data.Name = name
+	s.mu.Unlock()
+}
+
+// SetStatus sets the status of the span, if it is recording events.
+func (s *Span) SetStatus(status Status) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.mu.Lock()
+	s.data.Status = status
+	s.mu.Unlock()
+}
+
+func (s *Span) interfaceArrayToLinksArray() []Link {
+	linksArr := make([]Link, 0)
+	for _, value := range s.links.queue {
+		linksArr = append(linksArr, value.(Link))
+	}
+	return linksArr
+}
+
+func (s *Span) interfaceArrayToMessageEventArray() []MessageEvent {
+	messageEventArr := make([]MessageEvent, 0)
+	for _, value := range s.messageEvents.queue {
+		messageEventArr = append(messageEventArr, value.(MessageEvent))
+	}
+	return messageEventArr
+}
+
+func (s *Span) interfaceArrayToAnnotationArray() []Annotation {
+	annotationArr := make([]Annotation, 0)
+	for _, value := range s.annotations.queue {
+		annotationArr = append(annotationArr, value.(Annotation))
+	}
+	return annotationArr
+}
+
+func (s *Span) lruAttributesToAttributeMap() map[string]interface{} {
+	attributes := make(map[string]interface{})
+	for _, key := range s.lruAttributes.keys() {
+		value, ok := s.lruAttributes.get(key)
+		if ok {
+			keyStr := key.(string)
+			attributes[keyStr] = value
+		}
+	}
+	return attributes
+}
+
+func (s *Span) copyToCappedAttributes(attributes []Attribute) {
+	for _, a := range attributes {
+		s.lruAttributes.add(a.key, a.value)
+	}
+}
+
+func (s *Span) addChild() {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.mu.Lock()
+	s.data.ChildSpanCount++
+	s.mu.Unlock()
+}
+
+// AddAttributes sets attributes in the span.
+//
+// Existing attributes whose keys appear in the attributes parameter are overwritten.
+func (s *Span) AddAttributes(attributes ...Attribute) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.mu.Lock()
+	s.copyToCappedAttributes(attributes)
+	s.mu.Unlock()
+}
+
+// copyAttributes copies a slice of Attributes into a map.
+func copyAttributes(m map[string]interface{}, attributes []Attribute) {
+	for _, a := range attributes {
+		m[a.key] = a.value
+	}
+}
+
+func (s *Span) lazyPrintfInternal(attributes []Attribute, format string, a ...interface{}) {
+	now := time.Now()
+	msg := fmt.Sprintf(format, a...)
+	var m map[string]interface{}
+	s.mu.Lock()
+	if len(attributes) != 0 {
+		m = make(map[string]interface{})
+		copyAttributes(m, attributes)
+	}
+	s.annotations.add(Annotation{
+		Time:       now,
+		Message:    msg,
+		Attributes: m,
+	})
+	s.mu.Unlock()
+}
+
+func (s *Span) printStringInternal(attributes []Attribute, str string) {
+	now := time.Now()
+	var a map[string]interface{}
+	s.mu.Lock()
+	if len(attributes) != 0 {
+		a = make(map[string]interface{})
+		copyAttributes(a, attributes)
+	}
+	s.annotations.add(Annotation{
+		Time:       now,
+		Message:    str,
+		Attributes: a,
+	})
+	s.mu.Unlock()
+}
+
+// Annotate adds an annotation with attributes.
+// Attributes can be nil.
+func (s *Span) Annotate(attributes []Attribute, str string) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.printStringInternal(attributes, str)
+}
+
+// Annotatef adds an annotation with attributes.
+func (s *Span) Annotatef(attributes []Attribute, format string, a ...interface{}) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.lazyPrintfInternal(attributes, format, a...)
+}
+
+// AddMessageSendEvent adds a message send event to the span.
+//
+// messageID is an identifier for the message, which is recommended to be
+// unique in this span and the same between the send event and the receive
+// event (this allows to identify a message between the sender and receiver).
+// For example, this could be a sequence id.
+func (s *Span) AddMessageSendEvent(messageID, uncompressedByteSize, compressedByteSize int64) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	now := time.Now()
+	s.mu.Lock()
+	s.messageEvents.add(MessageEvent{
+		Time:                 now,
+		EventType:            MessageEventTypeSent,
+		MessageID:            messageID,
+		UncompressedByteSize: uncompressedByteSize,
+		CompressedByteSize:   compressedByteSize,
+	})
+	s.mu.Unlock()
+}
+
+// AddMessageReceiveEvent adds a message receive event to the span.
+//
+// messageID is an identifier for the message, which is recommended to be
+// unique in this span and the same between the send event and the receive
+// event (this allows to identify a message between the sender and receiver).
+// For example, this could be a sequence id.
+func (s *Span) AddMessageReceiveEvent(messageID, uncompressedByteSize, compressedByteSize int64) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	now := time.Now()
+	s.mu.Lock()
+	s.messageEvents.add(MessageEvent{
+		Time:                 now,
+		EventType:            MessageEventTypeRecv,
+		MessageID:            messageID,
+		UncompressedByteSize: uncompressedByteSize,
+		CompressedByteSize:   compressedByteSize,
+	})
+	s.mu.Unlock()
+}
+
+// AddLink adds a link to the span.
+func (s *Span) AddLink(l Link) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.mu.Lock()
+	s.links.add(l)
+	s.mu.Unlock()
+}
+
+func (s *Span) String() string {
+	if s == nil {
+		return "<nil>"
+	}
+	if s.data == nil {
+		return fmt.Sprintf("span %s", s.spanContext.SpanID)
+	}
+	s.mu.Lock()
+	str := fmt.Sprintf("span %s %q", s.spanContext.SpanID, s.data.Name)
+	s.mu.Unlock()
+	return str
+}
+
+var config atomic.Value // access atomically
+
+func init() {
+	gen := &defaultIDGenerator{}
+	// initialize traceID and spanID generators.
+	var rngSeed int64
+	for _, p := range []interface{}{
+		&rngSeed, &gen.traceIDAdd, &gen.nextSpanID, &gen.spanIDInc,
+	} {
+		binary.Read(crand.Reader, binary.LittleEndian, p)
+	}
+	gen.traceIDRand = rand.New(rand.NewSource(rngSeed))
+	gen.spanIDInc |= 1
+
+	config.Store(&Config{
+		DefaultSampler:             ProbabilitySampler(defaultSamplingProbability),
+		IDGenerator:                gen,
+		MaxAttributesPerSpan:       DefaultMaxAttributesPerSpan,
+		MaxAnnotationEventsPerSpan: DefaultMaxAnnotationEventsPerSpan,
+		MaxMessageEventsPerSpan:    DefaultMaxMessageEventsPerSpan,
+		MaxLinksPerSpan:            DefaultMaxLinksPerSpan,
+	})
+}
+
+type defaultIDGenerator struct {
+	sync.Mutex
+
+	// Please keep these as the first fields
+	// so that these 8 byte fields will be aligned on addresses
+	// divisible by 8, on both 32-bit and 64-bit machines when
+	// performing atomic increments and accesses.
+	// See:
+	// * https://github.com/census-instrumentation/opencensus-go/issues/587
+	// * https://github.com/census-instrumentation/opencensus-go/issues/865
+	// * https://golang.org/pkg/sync/atomic/#pkg-note-BUG
+	nextSpanID uint64
+	spanIDInc  uint64
+
+	traceIDAdd  [2]uint64
+	traceIDRand *rand.Rand
+}
+
+// NewSpanID returns a non-zero span ID from a randomly-chosen sequence.
+func (gen *defaultIDGenerator) NewSpanID() [8]byte {
+	var id uint64
+	for id == 0 {
+		id = atomic.AddUint64(&gen.nextSpanID, gen.spanIDInc)
+	}
+	var sid [8]byte
+	binary.LittleEndian.PutUint64(sid[:], id)
+	return sid
+}
+
+// NewTraceID returns a non-zero trace ID from a randomly-chosen sequence.
+// mu should be held while this function is called.
+func (gen *defaultIDGenerator) NewTraceID() [16]byte {
+	var tid [16]byte
+	// Construct the trace ID from two outputs of traceIDRand, with a constant
+	// added to each half for additional entropy.
+	gen.Lock()
+	binary.LittleEndian.PutUint64(tid[0:8], gen.traceIDRand.Uint64()+gen.traceIDAdd[0])
+	binary.LittleEndian.PutUint64(tid[8:16], gen.traceIDRand.Uint64()+gen.traceIDAdd[1])
+	gen.Unlock()
+	return tid
+}