b3

Documentation

Overview

This package implements the B3 propagator specification as defined at https://github.com/openzipkin/b3-propagation

Index

• type B3
  • func (b3 B3) Extract(ctx context.Context, carrier propagation.TextMapCarrier) context.Context
  • func (b3 B3) Fields() []string
  • func (b3 B3) Inject(ctx context.Context, carrier propagation.TextMapCarrier)
• type Encoding

Examples

• B3
• B3 (InjectEncoding)

Types

type B3

type B3 struct {
	// InjectEncoding are the B3 encodings used when injecting trace
	// information. If no encoding is specified (i.e. `B3Unspecified`)
	// `B3MultipleHeader` will be used as the default.
	InjectEncoding Encoding
}

B3 propagator serializes SpanContext to/from B3 Headers. This propagator supports both versions of B3 headers,

1. Single Header: b3: {TraceId}-{SpanId}-{SamplingState}-{ParentSpanId}
2. Multiple Headers: x-b3-traceid: {TraceId} x-b3-parentspanid: {ParentSpanId} x-b3-spanid: {SpanId} x-b3-sampled: {SamplingState} x-b3-flags: {DebugFlag}

Example

package main

import (
	"go.opentelemetry.io/contrib/propagators/b3"
	"go.opentelemetry.io/otel"
)

func main() {
	b3 := b3.B3{}
	// Register the B3 propagator globally.
	otel.SetTextMapPropagator(b3)
}

Example (InjectEncoding)

package main

import (
	"go.opentelemetry.io/contrib/propagators/b3"
	"go.opentelemetry.io/otel"
)

func main() {
	// Create a B3 propagator configured to inject context with both multiple
	// and single header B3 HTTP encoding.
	b3 := b3.B3{
		InjectEncoding: b3.B3MultipleHeader | b3.B3SingleHeader,
	}
	otel.SetTextMapPropagator(b3)
}

func (B3) Extract

func (b3 B3) Extract(ctx context.Context, carrier propagation.TextMapCarrier) context.Context

Extract extracts a context from the carrier if it contains B3 headers.

func (B3) Fields

func (b3 B3) Fields() []string

func (B3) Inject

func (b3 B3) Inject(ctx context.Context, carrier propagation.TextMapCarrier)

Inject injects a context into the carrier as B3 headers. The parent span ID is omitted because it is not tracked in the SpanContext.

type Encoding

type Encoding uint8

Encoding is a bitmask representation of the B3 encoding type.

const (
	// B3MultipleHeader is a B3 encoding that uses multiple headers to
	// transmit tracing information all prefixed with `x-b3-`.
	B3MultipleHeader Encoding = 1 << iota
	// B3SingleHeader is a B3 encoding that uses a single header named `b3`
	// to transmit tracing information.
	B3SingleHeader
	// B3Unspecified is an unspecified B3 encoding.
	B3Unspecified Encoding = 0
)