trace

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Version: v1.0.1 Latest Latest
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Published: Oct 1, 2021 License: Apache-2.0 Imports: 20 Imported by: 284

Documentation

Overview

Package trace contains support for OpenTelemetry distributed tracing.

The following assumes a basic familiarity with OpenTelemetry concepts. See https://opentelemetry.io.

Index

Examples

Constants

View Source
const (
	DefaultMaxQueueSize       = 2048
	DefaultBatchTimeout       = 5000 * time.Millisecond
	DefaultExportTimeout      = 30000 * time.Millisecond
	DefaultMaxExportBatchSize = 512
)

Defaults for BatchSpanProcessorOptions.

View Source
const (
	// DefaultAttributeCountLimit is the default maximum allowed span attribute count.
	DefaultAttributeCountLimit = 128

	// DefaultEventCountLimit is the default maximum allowed span event count.
	DefaultEventCountLimit = 128

	// DefaultLinkCountLimit is the default maximum allowed span link count.
	DefaultLinkCountLimit = 128

	// DefaultAttributePerEventCountLimit is the default maximum allowed attribute per span event count.
	DefaultAttributePerEventCountLimit = 128

	// DefaultAttributePerLinkCountLimit is the default maximum allowed attribute per span link count.
	DefaultAttributePerLinkCountLimit = 128
)

Variables

This section is empty.

Functions

This section is empty.

Types

type BatchSpanProcessorOption

type BatchSpanProcessorOption func(o *BatchSpanProcessorOptions)

func WithBatchTimeout

func WithBatchTimeout(delay time.Duration) BatchSpanProcessorOption

func WithBlocking

func WithBlocking() BatchSpanProcessorOption

func WithExportTimeout added in v0.20.0

func WithExportTimeout(timeout time.Duration) BatchSpanProcessorOption

func WithMaxExportBatchSize

func WithMaxExportBatchSize(size int) BatchSpanProcessorOption

func WithMaxQueueSize

func WithMaxQueueSize(size int) BatchSpanProcessorOption

type BatchSpanProcessorOptions

type BatchSpanProcessorOptions struct {
	// MaxQueueSize is the maximum queue size to buffer spans for delayed processing. If the
	// queue gets full it drops the spans. Use BlockOnQueueFull to change this behavior.
	// The default value of MaxQueueSize is 2048.
	MaxQueueSize int

	// BatchTimeout is the maximum duration for constructing a batch. Processor
	// forcefully sends available spans when timeout is reached.
	// The default value of BatchTimeout is 5000 msec.
	BatchTimeout time.Duration

	// ExportTimeout specifies the maximum duration for exporting spans. If the timeout
	// is reached, the export will be cancelled.
	// The default value of ExportTimeout is 30000 msec.
	ExportTimeout time.Duration

	// MaxExportBatchSize is the maximum number of spans to process in a single batch.
	// If there are more than one batch worth of spans then it processes multiple batches
	// of spans one batch after the other without any delay.
	// The default value of MaxExportBatchSize is 512.
	MaxExportBatchSize int

	// BlockOnQueueFull blocks onEnd() and onStart() method if the queue is full
	// AND if BlockOnQueueFull is set to true.
	// Blocking option should be used carefully as it can severely affect the performance of an
	// application.
	BlockOnQueueFull bool
}

type Event added in v1.0.0

type Event struct {
	// Name is the name of this event
	Name string

	// Attributes describe the aspects of the event.
	Attributes []attribute.KeyValue

	// DroppedAttributeCount is the number of attributes that were not
	// recorded due to configured limits being reached.
	DroppedAttributeCount int

	// Time at which this event was recorded.
	Time time.Time
}

Event is a thing that happened during a Span's lifetime.

type IDGenerator added in v0.15.0

type IDGenerator interface {

	// NewIDs returns a new trace and span ID.
	NewIDs(ctx context.Context) (trace.TraceID, trace.SpanID)

	// NewSpanID returns a ID for a new span in the trace with traceID.
	NewSpanID(ctx context.Context, traceID trace.TraceID) trace.SpanID
}

IDGenerator allows custom generators for TraceID and SpanID.

type Link struct {
	// SpanContext of the linked Span.
	SpanContext trace.SpanContext

	// Attributes describe the aspects of the link.
	Attributes []attribute.KeyValue

	// DroppedAttributeCount is the number of attributes that were not
	// recorded due to configured limits being reached.
	DroppedAttributeCount int
}

Link is the relationship between two Spans. The relationship can be within the same Trace or across different Traces.

type ParentBasedSamplerOption added in v0.12.0

type ParentBasedSamplerOption interface {
	// contains filtered or unexported methods
}

ParentBasedSamplerOption configures the sampler for a particular sampling case.

func WithLocalParentNotSampled added in v0.12.0

func WithLocalParentNotSampled(s Sampler) ParentBasedSamplerOption

WithLocalParentNotSampled sets the sampler for the case of local parent which is not sampled.

func WithLocalParentSampled added in v0.12.0

func WithLocalParentSampled(s Sampler) ParentBasedSamplerOption

WithLocalParentSampled sets the sampler for the case of sampled local parent.

func WithRemoteParentNotSampled added in v0.12.0

func WithRemoteParentNotSampled(s Sampler) ParentBasedSamplerOption

WithRemoteParentNotSampled sets the sampler for the case of remote parent which is not sampled.

func WithRemoteParentSampled added in v0.12.0

func WithRemoteParentSampled(s Sampler) ParentBasedSamplerOption

WithRemoteParentSampled sets the sampler for the case of sampled remote parent.

type ReadOnlySpan added in v0.16.0

type ReadOnlySpan interface {
	// Name returns the name of the span.
	Name() string
	// SpanContext returns the unique SpanContext that identifies the span.
	SpanContext() trace.SpanContext
	// Parent returns the unique SpanContext that identifies the parent of the
	// span if one exists. If the span has no parent the returned SpanContext
	// will be invalid.
	Parent() trace.SpanContext
	// SpanKind returns the role the span plays in a Trace.
	SpanKind() trace.SpanKind
	// StartTime returns the time the span started recording.
	StartTime() time.Time
	// EndTime returns the time the span stopped recording. It will be zero if
	// the span has not ended.
	EndTime() time.Time
	// Attributes returns the defining attributes of the span.
	Attributes() []attribute.KeyValue
	// Links returns all the links the span has to other spans.
	Links() []Link
	// Events returns all the events that occurred within in the spans
	// lifetime.
	Events() []Event
	// Status returns the spans status.
	Status() Status
	// InstrumentationLibrary returns information about the instrumentation
	// library that created the span.
	InstrumentationLibrary() instrumentation.Library
	// Resource returns information about the entity that produced the span.
	Resource() *resource.Resource
	// DroppedAttributes returns the number of attributes dropped by the span
	// due to limits being reached.
	DroppedAttributes() int
	// DroppedLinks returns the number of links dropped by the span due to
	// limits being reached.
	DroppedLinks() int
	// DroppedEvents returns the number of events dropped by the span due to
	// limits being reached.
	DroppedEvents() int
	// ChildSpanCount returns the count of spans that consider the span a
	// direct parent.
	ChildSpanCount() int
	// contains filtered or unexported methods
}

ReadOnlySpan allows reading information from the data structure underlying a trace.Span. It is used in places where reading information from a span is necessary but changing the span isn't necessary or allowed.

Warning: methods may be added to this interface in minor releases.

type ReadWriteSpan added in v0.16.0

type ReadWriteSpan interface {
	trace.Span
	ReadOnlySpan
}

ReadWriteSpan exposes the same methods as trace.Span and in addition allows reading information from the underlying data structure. This interface exposes the union of the methods of trace.Span (which is a "write-only" span) and ReadOnlySpan. New methods for writing or reading span information should be added under trace.Span or ReadOnlySpan, respectively.

Warning: methods may be added to this interface in minor releases.

type Sampler

type Sampler interface {

	// ShouldSample returns a SamplingResult based on a decision made from the
	// passed parameters.
	ShouldSample(parameters SamplingParameters) SamplingResult

	// Description returns information describing the Sampler.
	Description() string
}

Sampler decides whether a trace should be sampled and exported.

func AlwaysSample

func AlwaysSample() Sampler

AlwaysSample returns a Sampler that samples every trace. Be careful about using this sampler in a production application with significant traffic: a new trace will be started and exported for every request.

func NeverSample

func NeverSample() Sampler

NeverSample returns a Sampler that samples no traces.

func ParentBased added in v0.12.0

func ParentBased(root Sampler, samplers ...ParentBasedSamplerOption) Sampler

ParentBased returns a composite sampler which behaves differently, based on the parent of the span. If the span has no parent, the root(Sampler) is used to make sampling decision. If the span has a parent, depending on whether the parent is remote and whether it is sampled, one of the following samplers will apply: - remoteParentSampled(Sampler) (default: AlwaysOn) - remoteParentNotSampled(Sampler) (default: AlwaysOff) - localParentSampled(Sampler) (default: AlwaysOn) - localParentNotSampled(Sampler) (default: AlwaysOff)

func TraceIDRatioBased added in v0.12.0

func TraceIDRatioBased(fraction float64) Sampler

TraceIDRatioBased samples a given fraction of traces. Fractions >= 1 will always sample. Fractions < 0 are treated as zero. To respect the parent trace's `SampledFlag`, the `TraceIDRatioBased` sampler should be used as a delegate of a `Parent` sampler.

type SamplingDecision

type SamplingDecision uint8

SamplingDecision indicates whether a span is dropped, recorded and/or sampled.

const (
	// Drop will not record the span and all attributes/events will be dropped
	Drop SamplingDecision = iota

	// Record indicates the span's `IsRecording() == true`, but `Sampled` flag
	// *must not* be set
	RecordOnly

	// RecordAndSample has span's `IsRecording() == true` and `Sampled` flag
	// *must* be set
	RecordAndSample
)

Valid sampling decisions

type SamplingParameters

type SamplingParameters struct {
	ParentContext context.Context
	TraceID       trace.TraceID
	Name          string
	Kind          trace.SpanKind
	Attributes    []attribute.KeyValue
	Links         []trace.Link
}

SamplingParameters contains the values passed to a Sampler.

type SamplingResult

type SamplingResult struct {
	Decision   SamplingDecision
	Attributes []attribute.KeyValue
	Tracestate trace.TraceState
}

SamplingResult conveys a SamplingDecision, set of Attributes and a Tracestate.

type SpanExporter added in v0.20.0

type SpanExporter interface {

	// ExportSpans exports a batch of spans.
	//
	// This function is called synchronously, so there is no concurrency
	// safety requirement. However, due to the synchronous calling pattern,
	// it is critical that all timeouts and cancellations contained in the
	// passed context must be honored.
	//
	// Any retry logic must be contained in this function. The SDK that
	// calls this function will not implement any retry logic. All errors
	// returned by this function are considered unrecoverable and will be
	// reported to a configured error Handler.
	ExportSpans(ctx context.Context, spans []ReadOnlySpan) error

	// Shutdown notifies the exporter of a pending halt to operations. The
	// exporter is expected to preform any cleanup or synchronization it
	// requires while honoring all timeouts and cancellations contained in
	// the passed context.
	Shutdown(ctx context.Context) error
}

SpanExporter handles the delivery of spans to external receivers. This is the final component in the trace export pipeline.

type SpanLimits added in v0.18.0

type SpanLimits struct {
	// AttributeCountLimit is the maximum allowed span attribute count.
	AttributeCountLimit int

	// EventCountLimit is the maximum allowed span event count.
	EventCountLimit int

	// LinkCountLimit is the maximum allowed span link count.
	LinkCountLimit int

	// AttributePerEventCountLimit is the maximum allowed attribute per span event count.
	AttributePerEventCountLimit int

	// AttributePerLinkCountLimit is the maximum allowed attribute per span link count.
	AttributePerLinkCountLimit int
}

SpanLimits represents the limits of a span.

type SpanProcessor

type SpanProcessor interface {

	// OnStart is called when a span is started. It is called synchronously
	// and should not block.
	OnStart(parent context.Context, s ReadWriteSpan)

	// OnEnd is called when span is finished. It is called synchronously and
	// hence not block.
	OnEnd(s ReadOnlySpan)

	// Shutdown is called when the SDK shuts down. Any cleanup or release of
	// resources held by the processor should be done in this call.
	//
	// Calls to OnStart, OnEnd, or ForceFlush after this has been called
	// should be ignored.
	//
	// All timeouts and cancellations contained in ctx must be honored, this
	// should not block indefinitely.
	Shutdown(ctx context.Context) error

	// ForceFlush exports all ended spans to the configured Exporter that have not yet
	// been exported.  It should only be called when absolutely necessary, such as when
	// using a FaaS provider that may suspend the process after an invocation, but before
	// the Processor can export the completed spans.
	ForceFlush(ctx context.Context) error
}

SpanProcessor is a processing pipeline for spans in the trace signal. SpanProcessors registered with a TracerProvider and are called at the start and end of a Span's lifecycle, and are called in the order they are registered.

Example (Annotated)
package main

import (
	"context"
	"fmt"

	"go.opentelemetry.io/otel/attribute"
)

/*
Sometimes information about a runtime environment can change dynamically or be
delayed from startup. Instead of continuously recreating and distributing a
TracerProvider with an immutable Resource or delaying the startup of your
application on a slow-loading piece of information, annotate the created spans
dynamically using a SpanProcessor.
*/

var (
	// owner represents the owner of the application. In this example it is
	// stored as a simple string, but in real-world use this may be the
	// response to an asynchronous request.
	owner    = "unknown"
	ownerKey = attribute.Key("owner")
)

// Annotator is a SpanProcessor that adds attributes to all started spans.
type Annotator struct {
	// AttrsFunc is called when a span is started. The attributes it returns
	// are set on the Span being started.
	AttrsFunc func() []attribute.KeyValue
}

func (a Annotator) OnStart(_ context.Context, s ReadWriteSpan) { s.SetAttributes(a.AttrsFunc()...) }
func (a Annotator) Shutdown(context.Context) error             { return nil }
func (a Annotator) ForceFlush(context.Context) error           { return nil }
func (a Annotator) OnEnd(s ReadOnlySpan) {
	attr := s.Attributes()[0]
	fmt.Printf("%s: %s\n", attr.Key, attr.Value.AsString())
}

func main() {
	a := Annotator{
		AttrsFunc: func() []attribute.KeyValue {
			return []attribute.KeyValue{ownerKey.String(owner)}
		},
	}
	tracer := NewTracerProvider(WithSpanProcessor(a)).Tracer("annotated")

	// Simulate the situation where we want to annotate spans with an owner,
	// but at startup we do not now this information. Instead of waiting for
	// the owner to be known before starting and blocking here, start doing
	// work and update when the information becomes available.
	ctx := context.Background()
	_, s0 := tracer.Start(ctx, "span0")

	// Simulate an asynchronous call to determine the owner succeeding. We now
	// know that the owner of this application has been determined to be
	// Alice. Make sure all subsequent spans are annotated appropriately.
	owner = "alice"

	_, s1 := tracer.Start(ctx, "span1")
	s0.End()
	s1.End()

}
Output:

owner: unknown
owner: alice
Example (Filtered)
package main

import (
	"context"
	"time"
)

// DurationFilter is a SpanProcessor that filters spans that have lifetimes
// outside of a defined range.
type DurationFilter struct {
	// Next is the next SpanProcessor in the chain.
	Next SpanProcessor

	// Min is the duration under which spans are dropped.
	Min time.Duration
	// Max is the duration over which spans are dropped.
	Max time.Duration
}

func (f DurationFilter) OnStart(parent context.Context, s ReadWriteSpan) {
	f.Next.OnStart(parent, s)
}
func (f DurationFilter) Shutdown(ctx context.Context) error   { return f.Next.Shutdown(ctx) }
func (f DurationFilter) ForceFlush(ctx context.Context) error { return f.Next.ForceFlush(ctx) }
func (f DurationFilter) OnEnd(s ReadOnlySpan) {
	if f.Min > 0 && s.EndTime().Sub(s.StartTime()) < f.Min {
		// Drop short lived spans.
		return
	}
	if f.Max > 0 && s.EndTime().Sub(s.StartTime()) > f.Max {
		// Drop long lived spans.
		return
	}
	f.Next.OnEnd(s)
}

// InstrumentationBlacklist is a SpanProcessor that drops all spans from
// certain instrumentation.
type InstrumentationBlacklist struct {
	// Next is the next SpanProcessor in the chain.
	Next SpanProcessor

	// Blacklist is the set of instrumentation names for which spans will be
	// dropped.
	Blacklist map[string]bool
}

func (f InstrumentationBlacklist) OnStart(parent context.Context, s ReadWriteSpan) {
	f.Next.OnStart(parent, s)
}
func (f InstrumentationBlacklist) Shutdown(ctx context.Context) error { return f.Next.Shutdown(ctx) }
func (f InstrumentationBlacklist) ForceFlush(ctx context.Context) error {
	return f.Next.ForceFlush(ctx)
}
func (f InstrumentationBlacklist) OnEnd(s ReadOnlySpan) {
	if f.Blacklist != nil && f.Blacklist[s.InstrumentationLibrary().Name] {
		// Drop spans from this instrumentation
		return
	}
	f.Next.OnEnd(s)
}

type noopExporter struct{}

func (noopExporter) ExportSpans(context.Context, []ReadOnlySpan) error { return nil }
func (noopExporter) Shutdown(context.Context) error                    { return nil }

func main() {
	exportSP := NewSimpleSpanProcessor(noopExporter{})

	// Build a SpanProcessor chain to filter out all spans from the pernicious
	// "naughty-instrumentation" dependency and only allow spans shorter than
	// an minute and longer than a second to be exported with the exportSP.
	filter := DurationFilter{
		Next: InstrumentationBlacklist{
			Next: exportSP,
			Blacklist: map[string]bool{
				"naughty-instrumentation": true,
			},
		},
		Min: time.Second,
		Max: time.Minute,
	}

	_ = NewTracerProvider(WithSpanProcessor(filter))
	// ...
}
Output:

func NewBatchSpanProcessor

func NewBatchSpanProcessor(exporter SpanExporter, options ...BatchSpanProcessorOption) SpanProcessor

NewBatchSpanProcessor creates a new SpanProcessor that will send completed span batches to the exporter with the supplied options.

If the exporter is nil, the span processor will preform no action.

func NewSimpleSpanProcessor

func NewSimpleSpanProcessor(exporter SpanExporter) SpanProcessor

NewSimpleSpanProcessor returns a new SpanProcessor that will synchronously send completed spans to the exporter immediately.

This SpanProcessor is not recommended for production use. The synchronous nature of this SpanProcessor make it good for testing, debugging, or showing examples of other feature, but it will be slow and have a high computation resource usage overhead. The BatchSpanProcessor is recommended for production use instead.

type Status added in v1.0.0

type Status struct {
	// Code is an identifier of a Spans state classification.
	Code codes.Code
	// Description is a user hint about why that status was set. It is only
	// applicable when Code is Error.
	Description string
}

Status is the classified state of a Span.

type TracerProvider added in v0.12.0

type TracerProvider struct {
	// contains filtered or unexported fields
}

func NewTracerProvider added in v0.12.0

func NewTracerProvider(opts ...TracerProviderOption) *TracerProvider

NewTracerProvider returns a new and configured TracerProvider.

By default the returned TracerProvider is configured with:

- a ParentBased(AlwaysSample) Sampler
- a random number IDGenerator
- the resource.Default() Resource
- the default SpanLimits.

The passed opts are used to override these default values and configure the returned TracerProvider appropriately.

func (*TracerProvider) ForceFlush added in v0.19.0

func (p *TracerProvider) ForceFlush(ctx context.Context) error

ForceFlush immediately exports all spans that have not yet been exported for all the registered span processors.

func (*TracerProvider) RegisterSpanProcessor added in v0.12.0

func (p *TracerProvider) RegisterSpanProcessor(s SpanProcessor)

RegisterSpanProcessor adds the given SpanProcessor to the list of SpanProcessors

func (*TracerProvider) Shutdown added in v0.14.0

func (p *TracerProvider) Shutdown(ctx context.Context) error

Shutdown shuts down the span processors in the order they were registered.

func (*TracerProvider) Tracer added in v0.12.0

func (p *TracerProvider) Tracer(name string, opts ...trace.TracerOption) trace.Tracer

Tracer returns a Tracer with the given name and options. If a Tracer for the given name and options does not exist it is created, otherwise the existing Tracer is returned.

If name is empty, DefaultTracerName is used instead.

This method is safe to be called concurrently.

func (*TracerProvider) UnregisterSpanProcessor added in v0.12.0

func (p *TracerProvider) UnregisterSpanProcessor(s SpanProcessor)

UnregisterSpanProcessor removes the given SpanProcessor from the list of SpanProcessors

type TracerProviderOption added in v0.12.0

type TracerProviderOption interface {
	// contains filtered or unexported methods
}

func WithBatcher

WithBatcher registers the exporter with the TracerProvider using a BatchSpanProcessor configured with the passed opts.

func WithIDGenerator added in v0.15.0

func WithIDGenerator(g IDGenerator) TracerProviderOption

WithIDGenerator returns a TracerProviderOption that will configure the IDGenerator g as a TracerProvider's IDGenerator. The configured IDGenerator is used by the Tracers the TracerProvider creates to generate new Span and Trace IDs.

If this option is not used, the TracerProvider will use a random number IDGenerator by default.

func WithResource

func WithResource(r *resource.Resource) TracerProviderOption

WithResource returns a TracerProviderOption that will configure the Resource r as a TracerProvider's Resource. The configured Resource is referenced by all the Tracers the TracerProvider creates. It represents the entity producing telemetry.

If this option is not used, the TracerProvider will use the resource.Default() Resource by default.

func WithSampler added in v0.19.0

func WithSampler(s Sampler) TracerProviderOption

WithSampler returns a TracerProviderOption that will configure the Sampler s as a TracerProvider's Sampler. The configured Sampler is used by the Tracers the TracerProvider creates to make their sampling decisions for the Spans they create.

If this option is not used, the TracerProvider will use a ParentBased(AlwaysSample) Sampler by default.

func WithSpanLimits added in v0.19.0

func WithSpanLimits(sl SpanLimits) TracerProviderOption

WithSpanLimits returns a TracerProviderOption that will configure the SpanLimits sl as a TracerProvider's SpanLimits. The configured SpanLimits are used used by the Tracers the TracerProvider and the Spans they create to limit tracing resources used.

If this option is not used, the TracerProvider will use the default SpanLimits.

func WithSpanProcessor added in v0.12.0

func WithSpanProcessor(sp SpanProcessor) TracerProviderOption

WithSpanProcessor registers the SpanProcessor with a TracerProvider.

func WithSyncer

func WithSyncer(e SpanExporter) TracerProviderOption

WithSyncer registers the exporter with the TracerProvider using a SimpleSpanProcessor.

This is not recommended for production use. The synchronous nature of the SimpleSpanProcessor that will wrap the exporter make it good for testing, debugging, or showing examples of other feature, but it will be slow and have a high computation resource usage overhead. The WithBatcher option is recommended for production use instead.

Directories

Path Synopsis
Package tracetest is a testing helper package for the SDK.
Package tracetest is a testing helper package for the SDK.

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