forked from DataDog/dd-trace-go
/
tracer.go
416 lines (373 loc) · 12 KB
/
tracer.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 2016-2020 Datadog, Inc.
package tracer
import (
"os"
"strconv"
"sync"
"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/log"
"github.com/DataDog/datadog-go/statsd"
)
var _ ddtrace.Tracer = (*tracer)(nil)
// tracer creates, buffers and submits Spans which are used to time blocks of
// computation. They are accumulated and streamed into an internal payload,
// which is flushed to the agent whenever its size exceeds a specific threshold
// or when a certain interval of time has passed, whichever happens first.
//
// tracer operates based on a worker loop which responds to various request
// channels. It additionally holds two buffers which accumulates error and trace
// queues to be processed by the payload encoder.
type tracer struct {
*config
*payload
// payloadChan receives traces to be added to the payload.
payloadChan chan []*span
// climit limits the number of concurrent outgoing connections
climit chan struct{}
// stop causes the tracer to shut down when closed.
stop chan struct{}
// stopOnce ensures the tracer is stopped exactly once.
stopOnce sync.Once
// wg waits for all goroutines to exit when stopping.
wg sync.WaitGroup
// prioritySampling holds an instance of the priority sampler.
prioritySampling *prioritySampler
// pid of the process
pid string
// These integers track metrics about spans and traces as they are started,
// finished, and dropped
spansStarted, spansFinished, tracesDropped int64
// rulesSampling holds an instance of the rules sampler. These are user-defined
// rules for applying a sampling rate to spans that match the designated service
// or operation name.
rulesSampling *rulesSampler
}
const (
// flushInterval is the interval at which the payload contents will be flushed
// to the transport.
flushInterval = 2 * time.Second
// payloadMaxLimit is the maximum payload size allowed and should indicate the
// maximum size of the package that the agent can receive.
payloadMaxLimit = 9.5 * 1024 * 1024 // 9.5 MB
// payloadSizeLimit specifies the maximum allowed size of the payload before
// it will trigger a flush to the transport.
payloadSizeLimit = payloadMaxLimit / 2
// concurrentConnectionLimit specifies the maximum number of concurrent outgoing
// connections allowed.
concurrentConnectionLimit = 100
)
// statsInterval is the interval at which health metrics will be sent with the
// statsd client; replaced in tests.
var statsInterval = 10 * time.Second
// Start starts the tracer with the given set of options. It will stop and replace
// any running tracer, meaning that calling it several times will result in a restart
// of the tracer by replacing the current instance with a new one.
func Start(opts ...StartOption) {
if internal.Testing {
return // mock tracer active
}
internal.SetGlobalTracer(newTracer(opts...))
}
// Stop stops the started tracer. Subsequent calls are valid but become no-op.
func Stop() {
internal.SetGlobalTracer(&internal.NoopTracer{})
log.Flush()
}
// Span is an alias for ddtrace.Span. It is here to allow godoc to group methods returning
// ddtrace.Span. It is recommended and is considered more correct to refer to this type as
// ddtrace.Span instead.
type Span = ddtrace.Span
// StartSpan starts a new span with the given operation name and set of options.
// If the tracer is not started, calling this function is a no-op.
func StartSpan(operationName string, opts ...StartSpanOption) Span {
return internal.GetGlobalTracer().StartSpan(operationName, opts...)
}
// Extract extracts a SpanContext from the carrier. The carrier is expected
// to implement TextMapReader, otherwise an error is returned.
// If the tracer is not started, calling this function is a no-op.
func Extract(carrier interface{}) (ddtrace.SpanContext, error) {
return internal.GetGlobalTracer().Extract(carrier)
}
// Inject injects the given SpanContext into the carrier. The carrier is
// expected to implement TextMapWriter, otherwise an error is returned.
// If the tracer is not started, calling this function is a no-op.
func Inject(ctx ddtrace.SpanContext, carrier interface{}) error {
return internal.GetGlobalTracer().Inject(ctx, carrier)
}
// payloadQueueSize is the buffer size of the trace channel.
const payloadQueueSize = 1000
func newUnstartedTracer(opts ...StartOption) *tracer {
c := new(config)
defaults(c)
for _, fn := range opts {
fn(c)
}
if c.transport == nil {
c.transport = newTransport(c.agentAddr, c.httpClient)
}
if c.propagator == nil {
c.propagator = NewPropagator(nil)
}
if c.logger != nil {
log.UseLogger(c.logger)
}
if c.debug {
log.SetLevel(log.LevelDebug)
}
if c.statsd == nil {
client, err := statsd.New(c.dogstatsdAddr, statsd.WithMaxMessagesPerPayload(40), statsd.WithTags(statsTags(c)))
if err != nil {
log.Warn("Runtime and health metrics disabled: %v", err)
c.statsd = &statsd.NoOpClient{}
} else {
c.statsd = client
}
}
return &tracer{
config: c,
payload: newPayload(),
payloadChan: make(chan []*span, payloadQueueSize),
stop: make(chan struct{}),
rulesSampling: newRulesSampler(c.samplingRules),
climit: make(chan struct{}, concurrentConnectionLimit),
prioritySampling: newPrioritySampler(),
pid: strconv.Itoa(os.Getpid()),
}
}
func newTracer(opts ...StartOption) *tracer {
t := newUnstartedTracer(opts...)
c := t.config
t.config.statsd.Incr("datadog.tracer.started", nil, 1)
if c.runtimeMetrics {
log.Debug("Runtime metrics enabled.")
t.wg.Add(1)
go func() {
defer t.wg.Done()
t.reportRuntimeMetrics(defaultMetricsReportInterval)
}()
}
t.wg.Add(1)
go func() {
defer t.wg.Done()
tick := t.config.tickChan
if tick == nil {
ticker := time.NewTicker(flushInterval)
defer ticker.Stop()
tick = ticker.C
}
t.worker(tick)
}()
t.wg.Add(1)
go func() {
defer t.wg.Done()
t.reportHealthMetrics(statsInterval)
}()
return t
}
// worker receives finished traces to be added into the payload, as well
// as periodically flushes traces to the transport.
func (t *tracer) worker(tick <-chan time.Time) {
defer t.config.statsd.Close()
for {
select {
case trace := <-t.payloadChan:
t.pushPayload(trace)
case <-tick:
t.config.statsd.Incr("datadog.tracer.flush_triggered", []string{"reason:scheduled"}, 1)
t.flush()
case <-t.stop:
loop:
// the loop ensures that the payload channel is fully drained
// before the final flush to ensure no traces are lost (see #526)
for {
select {
case trace := <-t.payloadChan:
t.pushPayload(trace)
default:
break loop
}
}
t.config.statsd.Incr("datadog.tracer.flush_triggered", []string{"reason:shutdown"}, 1)
t.flush()
t.config.statsd.Incr("datadog.tracer.stopped", nil, 1)
return
}
}
}
func (t *tracer) pushTrace(trace []*span) {
select {
case <-t.stop:
return
default:
}
select {
case t.payloadChan <- trace:
default:
log.Error("payload queue full, dropping %d traces", len(trace))
}
}
// StartSpan creates, starts, and returns a new Span with the given `operationName`.
func (t *tracer) StartSpan(operationName string, options ...ddtrace.StartSpanOption) ddtrace.Span {
var opts ddtrace.StartSpanConfig
for _, fn := range options {
fn(&opts)
}
var startTime int64
if opts.StartTime.IsZero() {
startTime = now()
} else {
startTime = opts.StartTime.UnixNano()
}
var context *spanContext
if opts.Parent != nil {
if ctx, ok := opts.Parent.(*spanContext); ok {
context = ctx
}
}
id := opts.SpanID
if id == 0 {
id = random.Uint64()
}
// span defaults
span := &span{
Name: operationName,
Service: t.config.serviceName,
Resource: operationName,
SpanID: id,
TraceID: id,
Start: startTime,
taskEnd: startExecutionTracerTask(operationName),
}
if context != nil {
// this is a child span
span.TraceID = context.traceID
span.ParentID = context.spanID
if p, ok := context.samplingPriority(); ok {
span.setMetric(keySamplingPriority, float64(p))
}
if context.span != nil {
// local parent, inherit service
context.span.RLock()
span.Service = context.span.Service
context.span.RUnlock()
} else {
// remote parent
if context.origin != "" {
// mark origin
span.setMeta(keyOrigin, context.origin)
}
}
}
span.context = newSpanContext(span, context)
if context == nil || context.span == nil {
// this is either a root span or it has a remote parent, we should add the PID.
span.setMeta(ext.Pid, t.pid)
if t.hostname != "" {
span.setMeta(keyHostname, t.hostname)
}
if _, ok := opts.Tags[ext.ServiceName]; !ok && t.config.runtimeMetrics {
// this is a root span in the global service; runtime metrics should
// be linked to it:
span.setMeta("language", "go")
}
}
// add tags from options
for k, v := range opts.Tags {
span.SetTag(k, v)
}
// add global tags
for k, v := range t.config.globalTags {
span.SetTag(k, v)
}
if t.config.version != "" && span.Service == t.config.serviceName {
span.SetTag(ext.Version, t.config.version)
}
if context == nil {
// this is a brand new trace, sample it
t.sample(span)
}
return span
}
// Stop stops the tracer.
func (t *tracer) Stop() {
t.stopOnce.Do(func() {
close(t.stop)
})
t.wg.Wait()
}
// Inject uses the configured or default TextMap Propagator.
func (t *tracer) Inject(ctx ddtrace.SpanContext, carrier interface{}) error {
return t.config.propagator.Inject(ctx, carrier)
}
// Extract uses the configured or default TextMap Propagator.
func (t *tracer) Extract(carrier interface{}) (ddtrace.SpanContext, error) {
return t.config.propagator.Extract(carrier)
}
// flush will push any currently buffered traces to the server.
func (t *tracer) flush() {
if t.payload.itemCount() == 0 {
return
}
t.wg.Add(1)
t.climit <- struct{}{}
go func(p *payload) {
defer func(start time.Time) {
<-t.climit
t.wg.Done()
t.config.statsd.Timing("datadog.tracer.flush_duration", time.Since(start), nil, 1)
}(time.Now())
size, count := p.size(), p.itemCount()
log.Debug("Sending payload: size: %d traces: %d\n", size, count)
rc, err := t.config.transport.send(p)
if err != nil {
t.config.statsd.Count("datadog.tracer.traces_dropped", int64(count), []string{"reason:send_failed"}, 1)
log.Error("lost %d traces: %v", count, err)
} else {
t.config.statsd.Count("datadog.tracer.flush_bytes", int64(size), nil, 1)
t.config.statsd.Count("datadog.tracer.flush_traces", int64(count), nil, 1)
if err := t.prioritySampling.readRatesJSON(rc); err != nil {
t.config.statsd.Incr("datadog.tracer.decode_error", nil, 1)
}
}
}(t.payload)
t.payload = newPayload()
}
// pushPayload pushes the trace onto the payload. If the payload becomes
// larger than the threshold as a result, it sends a flush request.
func (t *tracer) pushPayload(trace []*span) {
if err := t.payload.push(trace); err != nil {
t.config.statsd.Incr("datadog.tracer.traces_dropped", []string{"reason:encoding_error"}, 1)
log.Error("error encoding msgpack: %v", err)
}
if t.payload.size() > payloadSizeLimit {
t.config.statsd.Incr("datadog.tracer.flush_triggered", []string{"reason:size"}, 1)
t.flush()
}
}
// sampleRateMetricKey is the metric key holding the applied sample rate. Has to be the same as the Agent.
const sampleRateMetricKey = "_sample_rate"
// Sample samples a span with the internal sampler.
func (t *tracer) sample(span *span) {
if _, ok := span.context.samplingPriority(); ok {
// sampling decision was already made
return
}
sampler := t.config.sampler
if !sampler.Sample(span) {
span.context.drop = true
return
}
if rs, ok := sampler.(RateSampler); ok && rs.Rate() < 1 {
span.setMetric(sampleRateMetricKey, rs.Rate())
}
if t.rulesSampling.apply(span) {
return
}
t.prioritySampling.apply(span)
}