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extractor.go
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extractor.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 2022-present Datadog, Inc.
package propagation
import (
"errors"
"fmt"
"net/http"
"strconv"
"github.com/DataDog/datadog-agent/pkg/serverless/trigger/events"
"github.com/DataDog/datadog-agent/pkg/trace/sampler"
"github.com/DataDog/datadog-agent/pkg/util/log"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
)
const (
defaultSamplingPriority sampler.SamplingPriority = sampler.PriorityNone
ddTraceIDHeader = "x-datadog-trace-id"
ddParentIDHeader = "x-datadog-parent-id"
ddSpanIDHeader = "x-datadog-span-id"
ddSamplingPriorityHeader = "x-datadog-sampling-priority"
ddInvocationErrorHeader = "x-datadog-invocation-error"
)
var (
errorUnsupportedExtractionType = errors.New("Unsupported event type for trace context extraction")
errorNoContextFound = errors.New("No trace context found")
errorNoSQSRecordFound = errors.New("No sqs message records found for trace context extraction")
errorNoSNSRecordFound = errors.New("No sns message records found for trace context extraction")
errorNoTraceIDFound = errors.New("No trace ID found")
errorNoParentIDFound = errors.New("No parent ID found")
)
// Extractor inserts trace context into and extracts trace context out of
// different types.
type Extractor struct {
propagator tracer.Propagator
}
// TraceContext stores the propagated trace context values.
type TraceContext struct {
TraceID uint64
ParentID uint64
SamplingPriority sampler.SamplingPriority
}
// TraceContextExtended stores the propagated trace context values plus other
// non-standard header values.
type TraceContextExtended struct {
*TraceContext
SpanID uint64
InvocationError bool
}
// Extract looks in the given events one by one and returns once a proper trace
// context is found.
func (e Extractor) Extract(events ...interface{}) (*TraceContext, error) {
for _, event := range events {
if tc, err := e.extract(event); err == nil {
return tc, nil
}
}
return nil, errorNoContextFound
}
// extract uses dd-trace-go's Propagator type to extract trace context from the
// given event.
func (e Extractor) extract(event interface{}) (*TraceContext, error) {
var carrier tracer.TextMapReader
var err error
switch ev := event.(type) {
case []byte:
carrier, err = rawPayloadCarrier(ev)
case events.SQSEvent:
// look for context in just the first message
if len(ev.Records) > 0 {
return e.extract(ev.Records[0])
}
return nil, errorNoSQSRecordFound
case events.SQSMessage:
if attr, ok := ev.Attributes[awsTraceHeader]; ok {
if tc, err := extractTraceContextfromAWSTraceHeader(attr); err == nil {
// Return early if AWSTraceHeader contains trace context
return tc, nil
}
}
carrier, err = sqsMessageCarrier(ev)
case events.SNSEvent:
// look for context in just the first message
if len(ev.Records) > 0 {
return e.extract(ev.Records[0].SNS)
}
return nil, errorNoSNSRecordFound
case events.SNSEntity:
carrier, err = snsEntityCarrier(ev)
case events.APIGatewayProxyRequest:
carrier, err = headersCarrier(ev.Headers)
case events.APIGatewayV2HTTPRequest:
carrier, err = headersCarrier(ev.Headers)
case events.APIGatewayWebsocketProxyRequest:
carrier, err = headersCarrier(ev.Headers)
case events.APIGatewayCustomAuthorizerRequestTypeRequest:
carrier, err = headersCarrier(ev.Headers)
case events.ALBTargetGroupRequest:
carrier, err = headersCarrier(ev.Headers)
case events.LambdaFunctionURLRequest:
carrier, err = headersCarrier(ev.Headers)
default:
err = errorUnsupportedExtractionType
}
if err != nil {
return nil, err
}
if e.propagator == nil {
e.propagator = tracer.NewPropagator(nil)
}
sc, err := e.propagator.Extract(carrier)
if err != nil {
return nil, err
}
return &TraceContext{
TraceID: sc.TraceID(),
ParentID: sc.SpanID(),
SamplingPriority: getSamplingPriority(sc),
}, nil
}
// ExtractFromLayer is used for extracting context from the request headers
// sent from a tracing layer. Currently, only datadog style headers are
// extracted. If a trace id or parent id are not found, then the embedded
// *TraceContext will be nil.
func (e Extractor) ExtractFromLayer(hdr http.Header) *TraceContextExtended {
tc, err := e.extractTraceContextFromLayer(hdr)
if err != nil {
log.Debugf("unable to find trace context in request headers: %s", err)
}
var spanID uint64
if value, err := convertStrToUint64(hdr.Get(ddSpanIDHeader)); err == nil {
log.Debugf("injecting spanId = %v", value)
spanID = value
}
invocationError := hdr.Get(ddInvocationErrorHeader) == "true"
return &TraceContextExtended{
TraceContext: tc,
SpanID: spanID,
InvocationError: invocationError,
}
}
func (e Extractor) extractTraceContextFromLayer(hdr http.Header) (*TraceContext, error) {
var traceID uint64
if value, err := convertStrToUint64(hdr.Get(ddTraceIDHeader)); err == nil {
log.Debugf("injecting traceID = %v", value)
traceID = value
}
if traceID == 0 {
return nil, errorNoTraceIDFound
}
var parentID uint64
if value, err := convertStrToUint64(hdr.Get(ddParentIDHeader)); err == nil {
log.Debugf("injecting parentId = %v", value)
parentID = value
}
if parentID == 0 {
return nil, errorNoParentIDFound
}
samplingPriority := defaultSamplingPriority
if value, err := strconv.ParseInt(hdr.Get(ddSamplingPriorityHeader), 10, 8); err == nil {
log.Debugf("injecting samplingPriority = %v", value)
samplingPriority = sampler.SamplingPriority(value)
}
return &TraceContext{
TraceID: traceID,
ParentID: parentID,
SamplingPriority: samplingPriority,
}, nil
}
// InjectToLayer is used for injecting context into the response headers sent
// to a tracing layer. Currently, only datadog style headers are injected.
func (e Extractor) InjectToLayer(tc *TraceContext, hdr http.Header) {
if tc != nil {
hdr.Set(ddTraceIDHeader, fmt.Sprintf("%v", tc.TraceID))
hdr.Set(ddSamplingPriorityHeader, fmt.Sprintf("%v", tc.SamplingPriority))
}
}
// getSamplingPriority searches the given ddtrace.SpanContext for sampling
// priority. Note that not all versions of ddtrace export the SamplingPriority
// method, therefore the interface check is required.
func getSamplingPriority(sc ddtrace.SpanContext) (priority sampler.SamplingPriority) {
priority = defaultSamplingPriority
if pc, ok := sc.(interface{ SamplingPriority() (int, bool) }); ok && pc != nil {
if p, ok := pc.SamplingPriority(); ok {
priority = sampler.SamplingPriority(p)
}
}
return
}
// convertStrToUint64 converts a given string to uint64 optionally returning an
// error.
func convertStrToUint64(s string) (uint64, error) {
num, err := strconv.ParseUint(s, 0, 64)
if err != nil {
log.Debugf("Error while converting %s, failing with : %s", s, err)
}
return num, err
}