Instana tracer implementation

vendor/github.com/opentracing/basictracer-go/tracer.go

@@ -0,0 +1,262 @@
+package basictracer
+
+import (
+	"time"
+
+	opentracing "github.com/opentracing/opentracing-go"
+)
+
+// Tracer extends the opentracing.Tracer interface with methods to
+// probe implementation state, for use by basictracer consumers.
+type Tracer interface {
+	opentracing.Tracer
+
+	// Options gets the Options used in New() or NewWithOptions().
+	Options() Options
+}
+
+// Options allows creating a customized Tracer via NewWithOptions. The object
+// must not be updated when there is an active tracer using it.
+type Options struct {
+	// ShouldSample is a function which is called when creating a new Span and
+	// determines whether that Span is sampled. The randomized TraceID is supplied
+	// to allow deterministic sampling decisions to be made across different nodes.
+	// For example,
+	//
+	//   func(traceID uint64) { return traceID % 64 == 0 }
+	//
+	// samples every 64th trace on average.
+	ShouldSample func(traceID uint64) bool
+	// TrimUnsampledSpans turns potentially expensive operations on unsampled
+	// Spans into no-ops. More precisely, tags and log events are silently
+	// discarded. If NewSpanEventListener is set, the callbacks will still fire.
+	TrimUnsampledSpans bool
+	// Recorder receives Spans which have been finished.
+	Recorder SpanRecorder
+	// NewSpanEventListener can be used to enhance the tracer by effectively
+	// attaching external code to trace events. See NetTraceIntegrator for a
+	// practical example, and event.go for the list of possible events.
+	NewSpanEventListener func() func(SpanEvent)
+	// DropAllLogs turns log events on all Spans into no-ops.
+	// If NewSpanEventListener is set, the callbacks will still fire.
+	DropAllLogs bool
+	// MaxLogsPerSpan limits the number of Logs in a span (if set to a nonzero
+	// value). If a span has more logs than this value, logs are dropped as
+	// necessary (and replaced with a log describing how many were dropped).
+	//
+	// About half of the MaxLogPerSpan logs kept are the oldest logs, and about
+	// half are the newest logs.
+	//
+	// If NewSpanEventListener is set, the callbacks will still fire for all log
+	// events. This value is ignored if DropAllLogs is true.
+	MaxLogsPerSpan int
+	// DebugAssertSingleGoroutine internally records the ID of the goroutine
+	// creating each Span and verifies that no operation is carried out on
+	// it on a different goroutine.
+	// Provided strictly for development purposes.
+	// Passing Spans between goroutine without proper synchronization often
+	// results in use-after-Finish() errors. For a simple example, consider the
+	// following pseudocode:
+	//
+	//  func (s *Server) Handle(req http.Request) error {
+	//    sp := s.StartSpan("server")
+	//    defer sp.Finish()
+	//    wait := s.queueProcessing(opentracing.ContextWithSpan(context.Background(), sp), req)
+	//    select {
+	//    case resp := <-wait:
+	//      return resp.Error
+	//    case <-time.After(10*time.Second):
+	//      sp.LogEvent("timed out waiting for processing")
+	//      return ErrTimedOut
+	//    }
+	//  }
+	//
+	// This looks reasonable at first, but a request which spends more than ten
+	// seconds in the queue is abandoned by the main goroutine and its trace
+	// finished, leading to use-after-finish when the request is finally
+	// processed. Note also that even joining on to a finished Span via
+	// StartSpanWithOptions constitutes an illegal operation.
+	//
+	// Code bases which do not require (or decide they do not want) Spans to
+	// be passed across goroutine boundaries can run with this flag enabled in
+	// tests to increase their chances of spotting wrong-doers.
+	DebugAssertSingleGoroutine bool
+	// DebugAssertUseAfterFinish is provided strictly for development purposes.
+	// When set, it attempts to exacerbate issues emanating from use of Spans
+	// after calling Finish by running additional assertions.
+	DebugAssertUseAfterFinish bool
+	// EnableSpanPool enables the use of a pool, so that the tracer reuses spans
+	// after Finish has been called on it. Adds a slight performance gain as it
+	// reduces allocations. However, if you have any use-after-finish race
+	// conditions the code may panic.
+	EnableSpanPool bool
+}
+
+// DefaultOptions returns an Options object with a 1 in 64 sampling rate and
+// all options disabled. A Recorder needs to be set manually before using the
+// returned object with a Tracer.
+func DefaultOptions() Options {
+	return Options{
+		ShouldSample:   func(traceID uint64) bool { return traceID%64 == 0 },
+		MaxLogsPerSpan: 100,
+	}
+}
+
+// NewWithOptions creates a customized Tracer.
+func NewWithOptions(opts Options) opentracing.Tracer {
+	rval := &tracerImpl{options: opts}
+	rval.textPropagator = &textMapPropagator{rval}
+	rval.binaryPropagator = &binaryPropagator{rval}
+	rval.accessorPropagator = &accessorPropagator{rval}
+	return rval
+}
+
+// New creates and returns a standard Tracer which defers completed Spans to
+// `recorder`.
+// Spans created by this Tracer support the ext.SamplingPriority tag: Setting
+// ext.SamplingPriority causes the Span to be Sampled from that point on.
+func New(recorder SpanRecorder) opentracing.Tracer {
+	opts := DefaultOptions()
+	opts.Recorder = recorder
+	return NewWithOptions(opts)
+}
+
+// Implements the `Tracer` interface.
+type tracerImpl struct {
+	options            Options
+	textPropagator     *textMapPropagator
+	binaryPropagator   *binaryPropagator
+	accessorPropagator *accessorPropagator
+}
+
+func (t *tracerImpl) StartSpan(
+	operationName string,
+	opts ...opentracing.StartSpanOption,
+) opentracing.Span {
+	sso := opentracing.StartSpanOptions{}
+	for _, o := range opts {
+		o.Apply(&sso)
+	}
+	return t.StartSpanWithOptions(operationName, sso)
+}
+
+func (t *tracerImpl) getSpan() *spanImpl {
+	if t.options.EnableSpanPool {
+		sp := spanPool.Get().(*spanImpl)
+		sp.reset()
+		return sp
+	}
+	return &spanImpl{}
+}
+
+func (t *tracerImpl) StartSpanWithOptions(
+	operationName string,
+	opts opentracing.StartSpanOptions,
+) opentracing.Span {
+	// Start time.
+	startTime := opts.StartTime
+	if startTime.IsZero() {
+		startTime = time.Now()
+	}
+
+	// Tags.
+	tags := opts.Tags
+
+	// Build the new span. This is the only allocation: We'll return this as
+	// an opentracing.Span.
+	sp := t.getSpan()
+	// Look for a parent in the list of References.
+	//
+	// TODO: would be nice if basictracer did something with all
+	// References, not just the first one.
+ReferencesLoop:
+	for _, ref := range opts.References {
+		switch ref.Type {
+		case opentracing.ChildOfRef,
+			opentracing.FollowsFromRef:
+
+			refCtx := ref.ReferencedContext.(SpanContext)
+			sp.raw.Context.TraceID = refCtx.TraceID
+			sp.raw.Context.SpanID = randomID()
+			sp.raw.Context.Sampled = refCtx.Sampled
+			sp.raw.ParentSpanID = refCtx.SpanID
+
+			if l := len(refCtx.Baggage); l > 0 {
+				sp.raw.Context.Baggage = make(map[string]string, l)
+				for k, v := range refCtx.Baggage {
+					sp.raw.Context.Baggage[k] = v
+				}
+			}
+			break ReferencesLoop
+		}
+	}
+	if sp.raw.Context.TraceID == 0 {
+		// No parent Span found; allocate new trace and span ids and determine
+		// the Sampled status.
+		sp.raw.Context.TraceID, sp.raw.Context.SpanID = randomID2()
+		sp.raw.Context.Sampled = t.options.ShouldSample(sp.raw.Context.TraceID)
+	}
+
+	return t.startSpanInternal(
+		sp,
+		operationName,
+		startTime,
+		tags,
+	)
+}
+
+func (t *tracerImpl) startSpanInternal(
+	sp *spanImpl,
+	operationName string,
+	startTime time.Time,
+	tags opentracing.Tags,
+) opentracing.Span {
+	sp.tracer = t
+	if t.options.NewSpanEventListener != nil {
+		sp.event = t.options.NewSpanEventListener()
+	}
+	sp.raw.Operation = operationName
+	sp.raw.Start = startTime
+	sp.raw.Duration = -1
+	sp.raw.Tags = tags
+	if t.options.DebugAssertSingleGoroutine {
+		sp.SetTag(debugGoroutineIDTag, curGoroutineID())
+	}
+	defer sp.onCreate(operationName)
+	return sp
+}
+
+type delegatorType struct{}
+
+// Delegator is the format to use for DelegatingCarrier.
+var Delegator delegatorType
+
+func (t *tracerImpl) Inject(sc opentracing.SpanContext, format interface{}, carrier interface{}) error {
+	switch format {
+	case opentracing.TextMap, opentracing.HTTPHeaders:
+		return t.textPropagator.Inject(sc, carrier)
+	case opentracing.Binary:
+		return t.binaryPropagator.Inject(sc, carrier)
+	}
+	if _, ok := format.(delegatorType); ok {
+		return t.accessorPropagator.Inject(sc, carrier)
+	}
+	return opentracing.ErrUnsupportedFormat
+}
+
+func (t *tracerImpl) Extract(format interface{}, carrier interface{}) (opentracing.SpanContext, error) {
+	switch format {
+	case opentracing.TextMap, opentracing.HTTPHeaders:
+		return t.textPropagator.Extract(carrier)
+	case opentracing.Binary:
+		return t.binaryPropagator.Extract(carrier)
+	}
+	if _, ok := format.(delegatorType); ok {
+		return t.accessorPropagator.Extract(carrier)
+	}
+	return nil, opentracing.ErrUnsupportedFormat
+}
+
+func (t *tracerImpl) Options() Options {
+	return t.options
+}