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span.go
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span.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.
//go:generate msgp -unexported -marshal=false -o=span_msgp.go -tests=false
package tracer
import (
"context"
"fmt"
"math"
"os"
"reflect"
"runtime"
"runtime/pprof"
"strconv"
"strings"
"sync"
"sync/atomic"
"time"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal"
"gopkg.in/DataDog/dd-trace-go.v1/internal/globalconfig"
"gopkg.in/DataDog/dd-trace-go.v1/internal/log"
"gopkg.in/DataDog/dd-trace-go.v1/internal/samplernames"
"github.com/DataDog/datadog-agent/pkg/obfuscate"
"github.com/tinylib/msgp/msgp"
"golang.org/x/xerrors"
)
type (
// spanList implements msgp.Encodable on top of a slice of spans.
spanList []*span
// spanLists implements msgp.Decodable on top of a slice of spanList.
// This type is only used in tests.
spanLists []spanList
)
var (
_ ddtrace.Span = (*span)(nil)
_ msgp.Encodable = (*spanList)(nil)
_ msgp.Decodable = (*spanLists)(nil)
)
// errorConfig holds customization options for setting error tags.
type errorConfig struct {
noDebugStack bool
stackFrames uint
stackSkip uint
}
// span represents a computation. Callers must call Finish when a span is
// complete to ensure it's submitted.
type span struct {
sync.RWMutex `msg:"-"`
Name string `msg:"name"` // operation name
Service string `msg:"service"` // service name (i.e. "grpc.server", "http.request")
Resource string `msg:"resource"` // resource name (i.e. "/user?id=123", "SELECT * FROM users")
Type string `msg:"type"` // protocol associated with the span (i.e. "web", "db", "cache")
Start int64 `msg:"start"` // span start time expressed in nanoseconds since epoch
Duration int64 `msg:"duration"` // duration of the span expressed in nanoseconds
Meta map[string]string `msg:"meta,omitempty"` // arbitrary map of metadata
Metrics map[string]float64 `msg:"metrics,omitempty"` // arbitrary map of numeric metrics
SpanID uint64 `msg:"span_id"` // identifier of this span
TraceID uint64 `msg:"trace_id"` // identifier of the root span
ParentID uint64 `msg:"parent_id"` // identifier of the span's direct parent
Error int32 `msg:"error"` // error status of the span; 0 means no errors
noDebugStack bool `msg:"-"` // disables debug stack traces
finished bool `msg:"-"` // true if the span has been submitted to a tracer.
context *spanContext `msg:"-"` // span propagation context
pprofCtxActive context.Context `msg:"-"` // contains pprof.WithLabel labels to tell the profiler more about this span
pprofCtxRestore context.Context `msg:"-"` // contains pprof.WithLabel labels of the parent span (if any) that need to be restored when this span finishes
taskEnd func() // ends execution tracer (runtime/trace) task, if started
}
// Context yields the SpanContext for this Span. Note that the return
// value of Context() is still valid after a call to Finish(). This is
// called the span context and it is different from Go's context.
func (s *span) Context() ddtrace.SpanContext { return s.context }
// SetBaggageItem sets a key/value pair as baggage on the span. Baggage items
// are propagated down to descendant spans and injected cross-process. Use with
// care as it adds extra load onto your tracing layer.
func (s *span) SetBaggageItem(key, val string) {
s.context.setBaggageItem(key, val)
}
// BaggageItem gets the value for a baggage item given its key. Returns the
// empty string if the value isn't found in this Span.
func (s *span) BaggageItem(key string) string {
return s.context.baggageItem(key)
}
// SetTag adds a set of key/value metadata to the span.
func (s *span) SetTag(key string, value interface{}) {
s.Lock()
defer s.Unlock()
// We don't lock spans when flushing, so we could have a data race when
// modifying a span as it's being flushed. This protects us against that
// race, since spans are marked `finished` before we flush them.
if s.finished {
return
}
switch key {
case ext.Error:
s.setTagError(value, errorConfig{
noDebugStack: s.noDebugStack,
})
return
}
if v, ok := value.(bool); ok {
s.setTagBool(key, v)
return
}
if v, ok := value.(string); ok {
s.setMeta(key, v)
return
}
if v, ok := toFloat64(value); ok {
s.setMetric(key, v)
return
}
if v, ok := value.(fmt.Stringer); ok {
defer func() {
if e := recover(); e != nil {
if v := reflect.ValueOf(value); v.Kind() == reflect.Ptr && v.IsNil() {
// If .String() panics due to a nil receiver, we want to catch this
// and replace the string value with "<nil>", just as Sprintf does.
// Other panics should not be handled.
s.setMeta(key, "<nil>")
return
}
panic(e)
}
}()
s.setMeta(key, v.String())
return
}
// not numeric, not a string, not a fmt.Stringer, not a bool, and not an error
s.setMeta(key, fmt.Sprint(value))
}
// setSamplingPriority locks then span, then updates the sampling priority.
// It also updates the trace's sampling priority.
func (s *span) setSamplingPriority(priority int, sampler samplernames.SamplerName, rate float64) {
s.Lock()
defer s.Unlock()
s.setSamplingPriorityLocked(priority, sampler, rate)
}
// setSamplingPriorityLocked updates the sampling priority.
// It also updates the trace's sampling priority.
func (s *span) setSamplingPriorityLocked(priority int, sampler samplernames.SamplerName, rate float64) {
// We don't lock spans when flushing, so we could have a data race when
// modifying a span as it's being flushed. This protects us against that
// race, since spans are marked `finished` before we flush them.
if s.finished {
return
}
s.setMetric(keySamplingPriority, float64(priority))
s.context.setSamplingPriority(s.Service, priority, sampler, rate)
}
// setTagError sets the error tag. It accounts for various valid scenarios.
// This method is not safe for concurrent use.
func (s *span) setTagError(value interface{}, cfg errorConfig) {
setError := func(yes bool) {
if yes {
if s.Error == 0 {
// new error
atomic.AddInt64(&s.context.errors, 1)
}
s.Error = 1
} else {
if s.Error > 0 {
// flip from active to inactive
atomic.AddInt64(&s.context.errors, -1)
}
s.Error = 0
}
}
if s.finished {
return
}
switch v := value.(type) {
case bool:
// bool value as per Opentracing spec.
setError(v)
case error:
// if anyone sets an error value as the tag, be nice here
// and provide all the benefits.
setError(true)
s.setMeta(ext.ErrorMsg, v.Error())
s.setMeta(ext.ErrorType, reflect.TypeOf(v).String())
if !cfg.noDebugStack {
s.setMeta(ext.ErrorStack, takeStacktrace(cfg.stackFrames, cfg.stackSkip))
}
switch v.(type) {
case xerrors.Formatter:
s.setMeta(ext.ErrorDetails, fmt.Sprintf("%+v", v))
case fmt.Formatter:
// pkg/errors approach
s.setMeta(ext.ErrorDetails, fmt.Sprintf("%+v", v))
}
case nil:
// no error
setError(false)
default:
// in all other cases, let's assume that setting this tag
// is the result of an error.
setError(true)
}
}
// defaultStackLength specifies the default maximum size of a stack trace.
const defaultStackLength = 32
// takeStacktrace takes a stack trace of maximum n entries, skipping the first skip entries.
// If n is 0, up to 20 entries are retrieved.
func takeStacktrace(n, skip uint) string {
if n == 0 {
n = defaultStackLength
}
var builder strings.Builder
pcs := make([]uintptr, n)
// +2 to exclude runtime.Callers and takeStacktrace
numFrames := runtime.Callers(2+int(skip), pcs)
if numFrames == 0 {
return ""
}
frames := runtime.CallersFrames(pcs[:numFrames])
for i := 0; ; i++ {
frame, more := frames.Next()
if i != 0 {
builder.WriteByte('\n')
}
builder.WriteString(frame.Function)
builder.WriteByte('\n')
builder.WriteByte('\t')
builder.WriteString(frame.File)
builder.WriteByte(':')
builder.WriteString(strconv.Itoa(frame.Line))
if !more {
break
}
}
return builder.String()
}
// setMeta sets a string tag. This method is not safe for concurrent use.
func (s *span) setMeta(key, v string) {
if s.Meta == nil {
s.Meta = make(map[string]string, 1)
}
delete(s.Metrics, key)
switch key {
case ext.SpanName:
s.Name = v
case ext.ServiceName:
s.Service = v
case ext.ResourceName:
s.Resource = v
case ext.SpanType:
s.Type = v
default:
s.Meta[key] = v
}
}
// setTagBool sets a boolean tag on the span.
func (s *span) setTagBool(key string, v bool) {
switch key {
case ext.AnalyticsEvent:
if v {
s.setMetric(ext.EventSampleRate, 1.0)
} else {
s.setMetric(ext.EventSampleRate, 0.0)
}
case ext.ManualDrop:
if v {
s.setSamplingPriorityLocked(ext.PriorityUserReject, samplernames.Manual, math.NaN())
}
case ext.ManualKeep:
if v {
s.setSamplingPriorityLocked(ext.PriorityUserKeep, samplernames.Manual, math.NaN())
}
default:
if v {
s.setMeta(key, "true")
} else {
s.setMeta(key, "false")
}
}
}
// setMetric sets a numeric tag, in our case called a metric. This method
// is not safe for concurrent use.
func (s *span) setMetric(key string, v float64) {
if s.Metrics == nil {
s.Metrics = make(map[string]float64, 1)
}
delete(s.Meta, key)
switch key {
case ext.ManualKeep:
if v == float64(samplernames.AppSec) {
s.setSamplingPriorityLocked(ext.PriorityUserKeep, samplernames.AppSec, math.NaN())
}
case ext.SamplingPriority:
// ext.SamplingPriority is deprecated in favor of ext.ManualKeep and ext.ManualDrop.
// We have it here for backward compatibility.
s.setSamplingPriorityLocked(int(v), samplernames.Manual, math.NaN())
default:
s.Metrics[key] = v
}
}
// Finish closes this Span (but not its children) providing the duration
// of its part of the tracing session.
func (s *span) Finish(opts ...ddtrace.FinishOption) {
t := now()
if len(opts) > 0 {
cfg := ddtrace.FinishConfig{
NoDebugStack: s.noDebugStack,
}
for _, fn := range opts {
fn(&cfg)
}
if !cfg.FinishTime.IsZero() {
t = cfg.FinishTime.UnixNano()
}
if cfg.Error != nil {
s.Lock()
s.setTagError(cfg.Error, errorConfig{
noDebugStack: cfg.NoDebugStack,
stackFrames: cfg.StackFrames,
stackSkip: cfg.SkipStackFrames,
})
s.Unlock()
}
}
if s.taskEnd != nil {
s.taskEnd()
}
s.finish(t)
if s.pprofCtxRestore != nil {
// Restore the labels of the parent span so any CPU samples after this
// point are attributed correctly.
pprof.SetGoroutineLabels(s.pprofCtxRestore)
}
}
// SetOperationName sets or changes the operation name.
func (s *span) SetOperationName(operationName string) {
s.Lock()
defer s.Unlock()
s.Name = operationName
}
func (s *span) finish(finishTime int64) {
s.Lock()
defer s.Unlock()
// We don't lock spans when flushing, so we could have a data race when
// modifying a span as it's being flushed. This protects us against that
// race, since spans are marked `finished` before we flush them.
if s.finished {
// already finished
return
}
if s.Duration == 0 {
s.Duration = finishTime - s.Start
}
if s.Duration < 0 {
s.Duration = 0
}
s.finished = true
keep := true
if t, ok := internal.GetGlobalTracer().(*tracer); ok {
// we have an active tracer
if t.config.canComputeStats() && shouldComputeStats(s) {
// the agent supports computed stats
select {
case t.stats.In <- newAggregableSpan(s, t.obfuscator):
// ok
default:
log.Error("Stats channel full, disregarding span.")
}
}
if t.config.canDropP0s() {
// the agent supports dropping p0's in the client
keep = shouldKeep(s)
}
}
if keep {
// a single kept span keeps the whole trace.
s.context.trace.keep()
}
s.context.finish()
}
// newAggregableSpan creates a new summary for the span s, within an application
// version version.
func newAggregableSpan(s *span, obfuscator *obfuscate.Obfuscator) *aggregableSpan {
var statusCode uint32
if sc, ok := s.Meta["http.status_code"]; ok && sc != "" {
if c, err := strconv.Atoi(sc); err == nil {
statusCode = uint32(c)
}
}
key := aggregation{
Name: s.Name,
Resource: obfuscatedResource(obfuscator, s.Type, s.Resource),
Service: s.Service,
Type: s.Type,
Synthetics: strings.HasPrefix(s.Meta[keyOrigin], "synthetics"),
StatusCode: statusCode,
}
return &aggregableSpan{
key: key,
Start: s.Start,
Duration: s.Duration,
TopLevel: s.Metrics[keyTopLevel] == 1,
Error: s.Error,
}
}
// textNonParsable specifies the text that will be assigned to resources for which the resource
// can not be parsed due to an obfuscation error.
const textNonParsable = "Non-parsable SQL query"
// obfuscatedResource returns the obfuscated version of the given resource. It is
// obfuscated using the given obfuscator for the given span type typ.
func obfuscatedResource(o *obfuscate.Obfuscator, typ, resource string) string {
if o == nil {
return resource
}
switch typ {
case "sql", "cassandra":
oq, err := o.ObfuscateSQLString(resource)
if err != nil {
log.Error("Error obfuscating stats group resource %q: %v", resource, err)
return textNonParsable
}
return oq.Query
case "redis":
return o.QuantizeRedisString(resource)
default:
return resource
}
}
// shouldKeep reports whether the trace should be kept.
// a single span being kept implies the whole trace being kept.
func shouldKeep(s *span) bool {
if p, ok := s.context.samplingPriority(); ok && p > 0 {
// positive sampling priorities stay
return true
}
if atomic.LoadInt64(&s.context.errors) > 0 {
// traces with any span containing an error get kept
return true
}
if v, ok := s.Metrics[ext.EventSampleRate]; ok {
return sampledByRate(s.TraceID, v)
}
return false
}
// shouldComputeStats mentions whether this span needs to have stats computed for.
// Warning: callers must guard!
func shouldComputeStats(s *span) bool {
if v, ok := s.Metrics[keyMeasured]; ok && v == 1 {
return true
}
if v, ok := s.Metrics[keyTopLevel]; ok && v == 1 {
return true
}
return false
}
// String returns a human readable representation of the span. Not for
// production, just debugging.
func (s *span) String() string {
lines := []string{
fmt.Sprintf("Name: %s", s.Name),
fmt.Sprintf("Service: %s", s.Service),
fmt.Sprintf("Resource: %s", s.Resource),
fmt.Sprintf("TraceID: %d", s.TraceID),
fmt.Sprintf("SpanID: %d", s.SpanID),
fmt.Sprintf("ParentID: %d", s.ParentID),
fmt.Sprintf("Start: %s", time.Unix(0, s.Start)),
fmt.Sprintf("Duration: %s", time.Duration(s.Duration)),
fmt.Sprintf("Error: %d", s.Error),
fmt.Sprintf("Type: %s", s.Type),
"Tags:",
}
s.RLock()
for key, val := range s.Meta {
lines = append(lines, fmt.Sprintf("\t%s:%s", key, val))
}
for key, val := range s.Metrics {
lines = append(lines, fmt.Sprintf("\t%s:%f", key, val))
}
s.RUnlock()
return strings.Join(lines, "\n")
}
// Format implements fmt.Formatter.
func (s *span) Format(f fmt.State, c rune) {
switch c {
case 's':
fmt.Fprint(f, s.String())
case 'v':
if svc := globalconfig.ServiceName(); svc != "" {
fmt.Fprintf(f, "dd.service=%s ", svc)
}
if tr, ok := internal.GetGlobalTracer().(*tracer); ok {
if tr.config.env != "" {
fmt.Fprintf(f, "dd.env=%s ", tr.config.env)
}
if tr.config.version != "" {
fmt.Fprintf(f, "dd.version=%s ", tr.config.version)
}
} else {
if env := os.Getenv("DD_ENV"); env != "" {
fmt.Fprintf(f, "dd.env=%s ", env)
}
if v := os.Getenv("DD_VERSION"); v != "" {
fmt.Fprintf(f, "dd.version=%s ", v)
}
}
fmt.Fprintf(f, `dd.trace_id="%d" dd.span_id="%d"`, s.TraceID, s.SpanID)
default:
fmt.Fprintf(f, "%%!%c(ddtrace.Span=%v)", c, s)
}
}
const (
keySamplingPriority = "_sampling_priority_v1"
keySamplingPriorityRate = "_dd.agent_psr"
keyUpstreamServices = "_dd.p.upstream_services"
keyOrigin = "_dd.origin"
keyHostname = "_dd.hostname"
keyRulesSamplerAppliedRate = "_dd.rule_psr"
keyRulesSamplerLimiterRate = "_dd.limit_psr"
keyMeasured = "_dd.measured"
// keyTopLevel is the key of top level metric indicating if a span is top level.
// A top level span is a local root (parent span of the local trace) or the first span of each service.
keyTopLevel = "_dd.top_level"
)