/
textmap.go
428 lines (388 loc) · 12 KB
/
textmap.go
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// Unless explicitly stated otherwise all files in this repository are licensed
// under the Apache License Version 2.0.
// This product includes software developed at Datadog (https://www.datadoghq.com/).
// Copyright 2016 Datadog, Inc.
package tracer
import (
"fmt"
"math"
"net/http"
"os"
"strconv"
"strings"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
"gopkg.in/DataDog/dd-trace-go.v1/internal/log"
"gopkg.in/DataDog/dd-trace-go.v1/internal/samplernames"
)
// HTTPHeadersCarrier wraps an http.Header as a TextMapWriter and TextMapReader, allowing
// it to be used using the provided Propagator implementation.
type HTTPHeadersCarrier http.Header
var _ TextMapWriter = (*HTTPHeadersCarrier)(nil)
var _ TextMapReader = (*HTTPHeadersCarrier)(nil)
// Set implements TextMapWriter.
func (c HTTPHeadersCarrier) Set(key, val string) {
http.Header(c).Set(key, val)
}
// ForeachKey implements TextMapReader.
func (c HTTPHeadersCarrier) ForeachKey(handler func(key, val string) error) error {
for k, vals := range c {
for _, v := range vals {
if err := handler(k, v); err != nil {
return err
}
}
}
return nil
}
// TextMapCarrier allows the use of a regular map[string]string as both TextMapWriter
// and TextMapReader, making it compatible with the provided Propagator.
type TextMapCarrier map[string]string
var _ TextMapWriter = (*TextMapCarrier)(nil)
var _ TextMapReader = (*TextMapCarrier)(nil)
// Set implements TextMapWriter.
func (c TextMapCarrier) Set(key, val string) {
c[key] = val
}
// ForeachKey conforms to the TextMapReader interface.
func (c TextMapCarrier) ForeachKey(handler func(key, val string) error) error {
for k, v := range c {
if err := handler(k, v); err != nil {
return err
}
}
return nil
}
const (
headerPropagationStyleInject = "DD_PROPAGATION_STYLE_INJECT"
headerPropagationStyleExtract = "DD_PROPAGATION_STYLE_EXTRACT"
)
const (
// DefaultBaggageHeaderPrefix specifies the prefix that will be used in
// HTTP headers or text maps to prefix baggage keys.
DefaultBaggageHeaderPrefix = "ot-baggage-"
// DefaultTraceIDHeader specifies the key that will be used in HTTP headers
// or text maps to store the trace ID.
DefaultTraceIDHeader = "x-datadog-trace-id"
// DefaultParentIDHeader specifies the key that will be used in HTTP headers
// or text maps to store the parent ID.
DefaultParentIDHeader = "x-datadog-parent-id"
// DefaultPriorityHeader specifies the key that will be used in HTTP headers
// or text maps to store the sampling priority value.
DefaultPriorityHeader = "x-datadog-sampling-priority"
)
// originHeader specifies the name of the header indicating the origin of the trace.
// It is used with the Synthetics product and usually has the value "synthetics".
const originHeader = "x-datadog-origin"
// traceTagsHeader holds the propagated trace tags
const traceTagsHeader = "x-datadog-tags"
// PropagatorConfig defines the configuration for initializing a propagator.
type PropagatorConfig struct {
// BaggagePrefix specifies the prefix that will be used to store baggage
// items in a map. It defaults to DefaultBaggageHeaderPrefix.
BaggagePrefix string
// TraceHeader specifies the map key that will be used to store the trace ID.
// It defaults to DefaultTraceIDHeader.
TraceHeader string
// ParentHeader specifies the map key that will be used to store the parent ID.
// It defaults to DefaultParentIDHeader.
ParentHeader string
// PriorityHeader specifies the map key that will be used to store the sampling priority.
// It defaults to DefaultPriorityHeader.
PriorityHeader string
// MaxTagsHeaderLen specifies the maximum length of trace tags header value.
MaxTagsHeaderLen int
// B3 specifies if B3 headers should be added for trace propagation
B3 bool
}
// NewPropagator returns a new propagator which uses TextMap to inject
// and extract values. It propagates trace and span IDs and baggage.
// To use the defaults, nil may be provided in place of the config.
func NewPropagator(cfg *PropagatorConfig) Propagator {
if cfg == nil {
cfg = new(PropagatorConfig)
}
if cfg.BaggagePrefix == "" {
cfg.BaggagePrefix = DefaultBaggageHeaderPrefix
}
if cfg.TraceHeader == "" {
cfg.TraceHeader = DefaultTraceIDHeader
}
if cfg.ParentHeader == "" {
cfg.ParentHeader = DefaultParentIDHeader
}
if cfg.PriorityHeader == "" {
cfg.PriorityHeader = DefaultPriorityHeader
}
return &chainedPropagator{
injectors: getPropagators(cfg, headerPropagationStyleInject),
extractors: getPropagators(cfg, headerPropagationStyleExtract),
}
}
// chainedPropagator implements Propagator and applies a list of injectors and extractors.
// When injecting, all injectors are called to propagate the span context.
// When extracting, it tries each extractor, selecting the first successful one.
type chainedPropagator struct {
injectors []Propagator
extractors []Propagator
}
// getPropagators returns a list of propagators based on the list found in the
// given environment variable. If the list doesn't contain any valid values the
// default propagator will be returned. Any invalid values in the list will log
// a warning and be ignored.
func getPropagators(cfg *PropagatorConfig, env string) []Propagator {
dd := &propagator{cfg}
ps := os.Getenv(env)
defaultPs := []Propagator{dd}
if cfg.B3 {
defaultPs = append(defaultPs, &propagatorB3{})
}
if ps == "" {
return defaultPs
}
var list []Propagator
if cfg.B3 {
list = append(list, &propagatorB3{})
}
for _, v := range strings.Split(ps, ",") {
switch strings.ToLower(v) {
case "datadog":
list = append(list, dd)
case "b3":
if !cfg.B3 {
// propagatorB3 hasn't already been added, add a new one.
list = append(list, &propagatorB3{})
}
default:
log.Warn("unrecognized propagator: %s\n", v)
}
}
if len(list) == 0 {
// return the default
return defaultPs
}
return list
}
// Inject defines the Propagator to propagate SpanContext data
// out of the current process. The implementation propagates the
// TraceID and the current active SpanID, as well as the Span baggage.
func (p *chainedPropagator) Inject(spanCtx ddtrace.SpanContext, carrier interface{}) error {
for _, v := range p.injectors {
err := v.Inject(spanCtx, carrier)
if err != nil {
return err
}
}
return nil
}
// Extract implements Propagator.
func (p *chainedPropagator) Extract(carrier interface{}) (ddtrace.SpanContext, error) {
for _, v := range p.extractors {
ctx, err := v.Extract(carrier)
if ctx != nil {
// first extractor returns
log.Debug("Extracted span context: %#v", ctx)
return ctx, nil
}
if err == ErrSpanContextNotFound {
continue
}
return nil, err
}
return nil, ErrSpanContextNotFound
}
// propagator implements Propagator and injects/extracts span contexts
// using datadog headers. Only TextMap carriers are supported.
type propagator struct {
cfg *PropagatorConfig
}
func (p *propagator) Inject(spanCtx ddtrace.SpanContext, carrier interface{}) error {
switch c := carrier.(type) {
case TextMapWriter:
return p.injectTextMap(spanCtx, c)
default:
return ErrInvalidCarrier
}
}
func (p *propagator) injectTextMap(spanCtx ddtrace.SpanContext, writer TextMapWriter) error {
ctx, ok := spanCtx.(*spanContext)
if !ok || ctx.traceID == 0 || ctx.spanID == 0 {
return ErrInvalidSpanContext
}
// propagate the TraceID and the current active SpanID
writer.Set(p.cfg.TraceHeader, strconv.FormatUint(ctx.traceID, 10))
writer.Set(p.cfg.ParentHeader, strconv.FormatUint(ctx.spanID, 10))
if sp, ok := ctx.samplingPriority(); ok {
writer.Set(p.cfg.PriorityHeader, strconv.Itoa(sp))
}
if ctx.origin != "" {
writer.Set(originHeader, ctx.origin)
}
// propagate OpenTracing baggage
for k, v := range ctx.baggage {
writer.Set(p.cfg.BaggagePrefix+k, v)
}
// propagate trace tags
var sb strings.Builder
if ctx.trace != nil {
ctx.trace.mu.RLock()
for k, v := range ctx.trace.tags {
if !strings.HasPrefix(k, "_dd.p.") {
continue
}
if err := isValidPropagatableTraceTag(k, v); err != nil {
log.Warn("won't propagate tag '%s' (err: %s)", k, err.Error())
continue
}
if sb.Len()+len(k)+len(v) > p.cfg.MaxTagsHeaderLen {
sb.Reset()
log.Warn("won't propagate trace tags (err: max trace tags header len (%d) reached)", p.cfg.MaxTagsHeaderLen)
break
}
if sb.Len() > 0 {
sb.WriteByte(',')
}
sb.WriteString(k)
sb.WriteByte('=')
sb.WriteString(v)
}
ctx.trace.mu.RUnlock()
if sb.Len() > 0 {
writer.Set(traceTagsHeader, sb.String())
}
}
return nil
}
func (p *propagator) Extract(carrier interface{}) (ddtrace.SpanContext, error) {
switch c := carrier.(type) {
case TextMapReader:
return p.extractTextMap(c)
default:
return nil, ErrInvalidCarrier
}
}
func (p *propagator) extractTextMap(reader TextMapReader) (ddtrace.SpanContext, error) {
var ctx spanContext
err := reader.ForeachKey(func(k, v string) error {
var err error
key := strings.ToLower(k)
switch key {
case p.cfg.TraceHeader:
ctx.traceID, err = parseUint64(v)
if err != nil {
return ErrSpanContextCorrupted
}
case p.cfg.ParentHeader:
ctx.spanID, err = parseUint64(v)
if err != nil {
return ErrSpanContextCorrupted
}
case p.cfg.PriorityHeader:
priority, err := strconv.Atoi(v)
if err != nil {
return ErrSpanContextCorrupted
}
ctx.setSamplingPriority("", priority, samplernames.Upstream, math.NaN())
case originHeader:
ctx.origin = v
case traceTagsHeader:
if ctx.trace == nil {
ctx.trace = newTrace()
}
ctx.trace.tags, err = parsePropagatableTraceTags(v)
ctx.trace.upstreamServices = ctx.trace.tags[keyUpstreamServices]
if err != nil {
log.Warn("did not extract trace tags (err: %s)", err.Error())
}
default:
if strings.HasPrefix(key, p.cfg.BaggagePrefix) {
ctx.setBaggageItem(strings.TrimPrefix(key, p.cfg.BaggagePrefix), v)
}
}
return nil
})
if err != nil {
return nil, err
}
if ctx.traceID == 0 || ctx.spanID == 0 {
return nil, ErrSpanContextNotFound
}
return &ctx, nil
}
const (
b3TraceIDHeader = "x-b3-traceid"
b3SpanIDHeader = "x-b3-spanid"
b3SampledHeader = "x-b3-sampled"
)
// propagatorB3 implements Propagator and injects/extracts span contexts
// using B3 headers. Only TextMap carriers are supported.
type propagatorB3 struct{}
func (p *propagatorB3) Inject(spanCtx ddtrace.SpanContext, carrier interface{}) error {
switch c := carrier.(type) {
case TextMapWriter:
return p.injectTextMap(spanCtx, c)
default:
return ErrInvalidCarrier
}
}
func (*propagatorB3) injectTextMap(spanCtx ddtrace.SpanContext, writer TextMapWriter) error {
ctx, ok := spanCtx.(*spanContext)
if !ok || ctx.traceID == 0 || ctx.spanID == 0 {
return ErrInvalidSpanContext
}
writer.Set(b3TraceIDHeader, fmt.Sprintf("%016x", ctx.traceID))
writer.Set(b3SpanIDHeader, fmt.Sprintf("%016x", ctx.spanID))
if p, ok := ctx.samplingPriority(); ok {
if p >= ext.PriorityAutoKeep {
writer.Set(b3SampledHeader, "1")
} else {
writer.Set(b3SampledHeader, "0")
}
}
return nil
}
func (p *propagatorB3) Extract(carrier interface{}) (ddtrace.SpanContext, error) {
switch c := carrier.(type) {
case TextMapReader:
return p.extractTextMap(c)
default:
return nil, ErrInvalidCarrier
}
}
func (*propagatorB3) extractTextMap(reader TextMapReader) (ddtrace.SpanContext, error) {
var ctx spanContext
err := reader.ForeachKey(func(k, v string) error {
var err error
key := strings.ToLower(k)
switch key {
case b3TraceIDHeader:
if len(v) > 16 {
v = v[len(v)-16:]
}
ctx.traceID, err = strconv.ParseUint(v, 16, 64)
if err != nil {
return ErrSpanContextCorrupted
}
case b3SpanIDHeader:
ctx.spanID, err = strconv.ParseUint(v, 16, 64)
if err != nil {
return ErrSpanContextCorrupted
}
case b3SampledHeader:
priority, err := strconv.Atoi(v)
if err != nil {
return ErrSpanContextCorrupted
}
ctx.setSamplingPriority("", priority, samplernames.Upstream, math.NaN())
default:
}
return nil
})
if err != nil {
return nil, err
}
if ctx.traceID == 0 || ctx.spanID == 0 {
return nil, ErrSpanContextNotFound
}
return &ctx, nil
}