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model.go
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model.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 2021 Datadog, Inc.
*/
package apm
import (
"encoding/json"
"fmt"
"strconv"
"strings"
"github.com/DataDog/datadog-agent/pkg/trace/event"
"github.com/DataDog/datadog-agent/pkg/trace/obfuscate"
"github.com/DataDog/datadog-agent/pkg/trace/pb"
"github.com/DataDog/datadog-agent/pkg/trace/sampler"
"github.com/DataDog/datadog-agent/pkg/trace/stats"
"github.com/DataDog/datadog-agent/pkg/trace/traceutil"
)
type (
// TraceList is an incoming trace payload
traceList struct {
Traces [][]span `json:"traces"`
}
// Span contains span metadata
span struct {
Service string `json:"service"`
Name string `json:"name"`
Resource string `json:"resource"`
TraceID string `json:"trace_id"`
SpanID string `json:"span_id"`
ParentID string `json:"parent_id"`
Start int64 `json:"start"`
Duration int64 `json:"duration"`
Error int32 `json:"error"`
Meta map[string]string `json:"meta"`
Metrics map[string]float64 `json:"metrics"`
Type string `json:"type"`
}
)
const (
originMetadataKey = "_dd.origin"
computeStatsKey = "_dd.compute_stats"
parentSourceMetadataKey = "_dd.parent_source"
sourceXray = "xray"
envMetadataKey = "env"
)
// ProcessTrace parses, applies tags, and obfuscates a trace
func ProcessTrace(content string, obfuscator *obfuscate.Obfuscator, tags string) ([]*pb.TracePayload, error) {
tracePayloads, err := ParseTrace(content)
if err != nil {
fmt.Printf("Couldn't forward trace: %v", err)
return tracePayloads, err
}
AddTagsToTracePayloads(tracePayloads, tags)
ObfuscatePayload(obfuscator, tracePayloads)
return tracePayloads, nil
}
// ParseTrace reads a trace using the standard log format
func ParseTrace(content string) ([]*pb.TracePayload, error) {
var tl traceList
err := json.Unmarshal([]byte(content), &tl)
traces := []*pb.TracePayload{}
if err != nil {
return traces, fmt.Errorf("couldn't parse trace, %v", err)
}
removedSpans := map[uint64]*pb.Span{}
for _, trace := range tl.Traces {
apiTraces := map[uint64]*pb.APITrace{}
env := "none"
for _, sp := range trace {
// Make sure the span is marked as comming from lambda,
// this will help the backend make sampling decisions
if sp.Meta == nil {
sp.Meta = map[string]string{}
}
sp.Meta[originMetadataKey] = "lambda"
// Instruct the span intake pipeline to compute stats
// in the APM backend.
sp.Meta[computeStatsKey] = "1"
// Use the env tag if it's present in the span metadata
if envValue, ok := sp.Meta[envMetadataKey]; ok {
env = envValue
}
pbSpan := convertSpanToPB(sp)
// We skip root dd-trace spans that are parented to X-Ray,
// since those root spans are placeholders for the X-Ray
// parent span.
if IsParentedToXray(pbSpan) {
removedSpans[pbSpan.SpanID] = pbSpan
continue
}
var apiTrace *pb.APITrace
var ok bool
// Reparent any spans that have been removed
if removedSpans[pbSpan.ParentID] != nil {
pbSpan.ParentID = removedSpans[pbSpan.ParentID].ParentID
}
if apiTrace, ok = apiTraces[pbSpan.TraceID]; !ok {
apiTrace = &pb.APITrace{
TraceID: pbSpan.TraceID,
Spans: []*pb.Span{},
StartTime: 0,
EndTime: 0,
}
apiTraces[apiTrace.TraceID] = apiTrace
}
addToAPITrace(apiTrace, pbSpan)
}
payload := pb.TracePayload{
HostName: "",
Env: env,
Traces: []*pb.APITrace{},
}
for _, apiTrace := range apiTraces {
computeSublayerMetrics(apiTrace.Spans)
payload.Traces = append(payload.Traces, apiTrace)
}
// We dont want to include TracePayloads with empty traces
if len(payload.Traces) == 0 {
continue
}
traces = append(traces, &payload)
}
return traces, nil
}
// IsParentedToXray detects whether the parent of a trace is an X-Ray span
func IsParentedToXray(span *pb.Span) bool {
if span.Meta == nil {
return false
}
source := span.Meta[parentSourceMetadataKey]
return source == sourceXray
}
// AddTagsToTracePayloads takes a single string of tags, eg 'a:b,c:d', and applies them
// to each span in a trace
func AddTagsToTracePayloads(tracePayloads []*pb.TracePayload, tags string) {
tagMap := map[string]string{}
tl := strings.Split(tags, ",")
service := ""
env := ""
for _, tag := range tl {
values := strings.SplitN(tag, ":", 2)
if len(values) < 2 {
continue
}
tag := values[0]
value := values[1]
if strings.ToLower(tag) == "service" {
service = value
} else if strings.ToLower(tag) == "env" {
env = value
} else {
tagMap[tag] = value
}
}
serviceLookup := map[string]string{}
if service != "" {
serviceLookup = buildServiceLookup(tracePayloads, service)
}
for _, tracePayload := range tracePayloads {
if env != "" && env != "none" {
tracePayload.Env = env
}
for _, trace := range tracePayload.Traces {
for _, span := range trace.Spans {
// do not add tags from Lambda function if it's an inferred span and
// it does not belong to the AWS Lambda service
if value, ok := span.Meta["_inferred_span.tag_source"]; ok && value == "self" {
continue
}
if serviceLookup[span.Service] != "" {
span.Service = serviceLookup[span.Service]
}
for tag, value := range tagMap {
span.Meta[tag] = value
}
if serviceLookup[span.Service] != "" && span.Meta["service"] != "" {
span.Meta["service"] = serviceLookup[span.Service]
}
}
}
}
}
// ObfuscatePayload applies obfuscator rules to the trace payloads
func ObfuscatePayload(obfuscator *obfuscate.Obfuscator, tracePayloads []*pb.TracePayload) {
for _, tracePayload := range tracePayloads {
// Obfuscate the traces in the payload
for _, trace := range tracePayload.Traces {
for _, span := range trace.Spans {
obfuscator.Obfuscate(span)
}
}
}
}
func buildServiceLookup(tracePayloads []*pb.TracePayload, service string) map[string]string {
remappedServices := map[string]string{}
for _, tracePayload := range tracePayloads {
for _, trace := range tracePayload.Traces {
for _, span := range trace.Spans {
if span.Name == "aws.lambda" || span.Service == "aws.lambda" {
remappedServices[span.Service] = service
}
}
}
}
for _, tracePayload := range tracePayloads {
for _, trace := range tracePayload.Traces {
for _, span := range trace.Spans {
for k := range remappedServices {
if strings.HasPrefix(span.Service, k) && span.Service != k && span.Service != "" {
remappedServices[span.Service] = strings.Replace(span.Service, k, service, 1)
}
}
}
}
}
return remappedServices
}
func convertSpanToPB(sp span) *pb.Span {
return &pb.Span{
Service: sp.Service,
Name: sp.Name,
Resource: sp.Resource,
TraceID: decodeAPMId(sp.TraceID),
SpanID: decodeAPMId(sp.SpanID),
ParentID: decodeAPMId(sp.ParentID),
Start: sp.Start,
Duration: sp.Duration,
Error: sp.Error,
Meta: sp.Meta,
Metrics: sp.Metrics,
Type: sp.Type,
}
}
func addToAPITrace(apiTrace *pb.APITrace, sp *pb.Span) {
apiTrace.Spans = append(apiTrace.Spans, sp)
endTime := sp.Start + sp.Duration
if apiTrace.EndTime > endTime {
apiTrace.EndTime = endTime
}
if apiTrace.StartTime == 0 || apiTrace.StartTime > sp.Start {
apiTrace.StartTime = sp.Start
}
}
func decodeAPMId(id string) uint64 {
if len(id) > 16 {
id = id[len(id)-16:]
}
val, err := strconv.ParseUint(id, 16, 64)
if err != nil {
return 0
}
return val
}
// GetAnalyzedSpans finds all the analyzed spans in a trace, including top level spans
// and spans marked as anaylzed by the tracer.
// A span is considered top-level if:
// - it's a root span
// - its parent is unknown (other part of the code, distributed trace)
// - its parent belongs to another service (in that case it's a "local root"
// being the highest ancestor of other spans belonging to this service and
// attached to it).
func GetAnalyzedSpans(sps []*pb.Span) []*pb.Span {
// build a lookup map
spanIDToIdx := make(map[uint64]int, len(sps))
for i, span := range sps {
spanIDToIdx[span.SpanID] = i
}
top := []*pb.Span{}
extractor := event.NewMetricBasedExtractor()
// iterate on each span and mark them as top-level if relevant
for _, span := range sps {
// The tracer can mark a span to be analysed, with a value 0-1, where 1 is always keep, and 0 is always reject.
// Values between 0-1 are used by the agent to prioritise which spans are sampled or not. Since we can't
// reliably apply sampling decisions in a serverless environment, we keep any analyzed span with a priority
// greater than 0, and let the backend make the sampling decision instead.
priority, extracted := extractor.Extract(span, sampler.PriorityUserKeep)
shouldExtract := priority > 0 && extracted
if span.ParentID != 0 {
if parentIdx, ok := spanIDToIdx[span.ParentID]; ok && sps[parentIdx].Service == span.Service && !shouldExtract {
continue
}
}
top = append(top, span)
}
return top
}
func computeSublayerMetrics(t pb.Trace) {
root := traceutil.GetRoot(t)
traceutil.ComputeTopLevel(t)
subtraces := stats.ExtractSubtraces(t, root)
sublayers := make(map[*pb.Span][]stats.SublayerValue)
for _, subtrace := range subtraces {
subtraceSublayers := stats.ComputeSublayers(subtrace.Trace)
sublayers[subtrace.Root] = subtraceSublayers
stats.SetSublayersOnSpan(subtrace.Root, subtraceSublayers)
}
}