basictracer

README

basictracer-go

The Go incarnation of the cross-platform "BasicTracer" reference implementation for OpenTracing.

Status

In early development: there will be backwards-incompatible changes so caveat emptor for now!

Documentation

Index

• Variables
• func New(recorder SpanRecorder) opentracing.Tracer
• func NewWithOptions(opts Options) opentracing.Tracer
• type Context
• type DelegatingCarrier
• type EventBaggage
• type EventCreate
• type EventFinish
• type EventLog
• type EventTag
• type Options
  • func DefaultOptions() Options
• type RawSpan
• type Span
• type SpanEvent
• type SpanRecorder
• type Tracer

Variables

var Delegator delegatorType

Delegator is the format to use for DelegatingCarrier.

var NetTraceIntegrator = func() func(SpanEvent) {
	var tr trace.Trace
	return func(e SpanEvent) {
		switch t := e.(type) {
		case EventCreate:
			tr = trace.New("tracing", t.OperationName)
		case EventFinish:
			tr.Finish()
		case EventLog:
			if t.Payload != nil {
				tr.LazyPrintf("%s (payload %v)", t.Event, t.Payload)
			} else {
				tr.LazyPrintf("%s", t.Event)
			}
		}
	}
}

NetTraceIntegrator can be passed into a basictracer as NewSpanEventListener and causes all traces to be registered with the net/trace endpoint.

Functions

func New

func New(recorder SpanRecorder) opentracing.Tracer

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 NewWithOptions

func NewWithOptions(opts Options) opentracing.Tracer

NewWithOptions creates a customized Tracer.

Types

type Context

type Context struct {
	// A probabilistically unique identifier for a [multi-span] trace.
	TraceID uint64

	// A probabilistically unique identifier for a span.
	SpanID uint64

	// The SpanID of this Context's parent, or 0 if there is no parent.
	ParentSpanID uint64

	// Whether the trace is sampled.
	Sampled bool
}

Context holds the basic Span metadata.

type DelegatingCarrier

type DelegatingCarrier interface {
	SetState(traceID, spanID uint64, sampled bool)
	State() (traceID, spanID uint64, sampled bool)
	SetBaggageItem(key, value string)
	GetBaggage(func(key, value string))
}

DelegatingCarrier is a flexible carrier interface which can be implemented by types which have a means of storing the trace metadata and already know how to serialize themselves (for example, protocol buffers).

type EventBaggage

type EventBaggage struct {
	Key, Value string
}

EventBaggage is received when SetBaggageItem is called.

type EventCreate

type EventCreate struct{ OperationName string }

EventCreate is emitted when a Span is created.

type EventFinish

type EventFinish RawSpan

EventFinish is received when Finish is called.

type EventLog

type EventLog opentracing.LogData

EventLog is received when Log (or one of its derivatives) is called.

type EventTag

type EventTag struct {
	Key   string
	Value interface{}
}

EventTag is received when SetTag is called.

type Options

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(uint64) bool
	// TrimUnsampledSpans turns potentially expensive operations on unsampled
	// Spans into no-ops. More precisely, tags, baggage items, and log events
	// are silently discarded. If NewSpanEventListener is set, the callbacks
	// will still fire in that case.
	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)
	// 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(), ctx), 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
}

Options allows creating a customized Tracer via NewWithOptions. The object must not be updated when there is an active tracer using it.

func DefaultOptions

func DefaultOptions() Options

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.

type RawSpan

type RawSpan struct {
	// The RawSpan embeds its Context. Those recording the RawSpan
	// should also record the contents of its Context.
	Context

	// The name of the "operation" this span is an instance of. (Called a "span
	// name" in some implementations)
	Operation string

	// We store <start, duration> rather than <start, end> so that only
	// one of the timestamps has global clock uncertainty issues.
	Start    time.Time
	Duration time.Duration

	// Essentially an extension mechanism. Can be used for many purposes,
	// not to be enumerated here.
	Tags opentracing.Tags

	// The span's "microlog".
	Logs []opentracing.LogData

	// The span's associated baggage.
	Baggage map[string]string // initialized on first use
}

RawSpan encapsulates all state associated with a (finished) Span.

type Span

type Span interface {
	opentracing.Span

	// Context contains trace identifiers
	Context() Context

	// Operation names the work done by this span instance
	Operation() string

	// Start indicates when the span began
	Start() time.Time
}

Span provides access to the essential details of the span, for use by basictracer consumers. These methods may only be called prior to (*opentracing.Span).Finish().

type SpanEvent

type SpanEvent interface{}

A SpanEvent is emitted when a mutating command is called on a Span.

type SpanRecorder

type SpanRecorder interface {
	// Implementations must determine whether and where to store `span`.
	RecordSpan(span RawSpan)
}

A SpanRecorder handles all of the `RawSpan` data generated via an associated `Tracer` (see `NewStandardTracer`) instance. It also names the containing process and provides access to a straightforward tag map.

type Tracer

type Tracer interface {
	opentracing.Tracer

	// Options gets the Options used in New() or NewWithOptions().
	Options() Options
}

Tracer extends the opentracing.Tracer interface with methods to probe implementation state, for use by basictracer consumers.