-
Notifications
You must be signed in to change notification settings - Fork 415
/
tracer.go
586 lines (534 loc) · 18.2 KB
/
tracer.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
// 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 (
gocontext "context"
"os"
"runtime/pprof"
rt "runtime/trace"
"strconv"
"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/appsec"
"gopkg.in/DataDog/dd-trace-go.v1/internal/log"
"gopkg.in/DataDog/dd-trace-go.v1/internal/traceprof"
"github.com/DataDog/datadog-agent/pkg/obfuscate"
)
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 *config
// stats specifies the concentrator used to compute statistics, when client-side
// stats are enabled.
stats *concentrator
// traceWriter is responsible for sending finished traces to their
// destination, such as the Trace Agent or Datadog Forwarder.
traceWriter traceWriter
// out receives finishedTrace with spans to be added to the payload.
out chan *finishedTrace
// flush receives a channel onto which it will confirm after a flush has been
// triggered and completed.
flush chan 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
// Records the number of dropped P0 traces and spans.
droppedP0Traces, droppedP0Spans uint64
// partialTrace the number of partially dropped traces.
partialTraces uint64
// rulesSampling holds an instance of the rules sampler used to apply either trace sampling,
// or single span sampling rules on spans. These are user-defined
// rules for applying a sampling rate to spans that match the designated service
// or operation name.
rulesSampling *rulesSampler
// obfuscator holds the obfuscator used to obfuscate resources in aggregated stats.
// obfuscator may be nil if disabled.
obfuscator *obfuscate.Obfuscator
}
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
}
t := newTracer(opts...)
if !t.config.enabled {
return
}
internal.SetGlobalTracer(t)
if t.config.logStartup {
logStartup(t)
}
}
// 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)
}
// SetUser associates user information to the current trace which the
// provided span belongs to. The options can be used to tune which user
// bit of information gets monitored. In case of distributed traces,
// the user id can be propagated across traces using the WithPropagation() option.
// See https://docs.datadoghq.com/security_platform/application_security/setup_and_configure/?tab=set_user#add-user-information-to-traces
func SetUser(s Span, id string, opts ...UserMonitoringOption) {
if s == nil {
return
}
sp, ok := s.(*span)
if !ok || sp.context == nil {
return
}
sp = sp.context.trace.root
var cfg UserMonitoringConfig
for _, fn := range opts {
fn(&cfg)
}
sp.setUser(id, cfg)
}
// payloadQueueSize is the buffer size of the trace channel.
const payloadQueueSize = 1000
func newUnstartedTracer(opts ...StartOption) *tracer {
c := newConfig(opts...)
sampler := newPrioritySampler()
var writer traceWriter
if c.logToStdout {
writer = newLogTraceWriter(c)
} else {
writer = newAgentTraceWriter(c, sampler)
}
traces, spans, err := samplingRulesFromEnv()
if err != nil {
log.Warn("DIAGNOSTICS Error(s) parsing sampling rules: found errors:%s", err)
}
if traces != nil {
c.traceRules = traces
}
if spans != nil {
c.spanRules = spans
}
t := &tracer{
config: c,
traceWriter: writer,
out: make(chan *finishedTrace, payloadQueueSize),
stop: make(chan struct{}),
flush: make(chan chan<- struct{}),
rulesSampling: newRulesSampler(c.traceRules, c.spanRules),
prioritySampling: sampler,
pid: strconv.Itoa(os.Getpid()),
stats: newConcentrator(c, defaultStatsBucketSize),
obfuscator: obfuscate.NewObfuscator(obfuscate.Config{
SQL: obfuscate.SQLConfig{
TableNames: c.agent.HasFlag("table_names"),
ReplaceDigits: c.agent.HasFlag("quantize_sql_tables") || c.agent.HasFlag("replace_sql_digits"),
KeepSQLAlias: c.agent.HasFlag("keep_sql_alias"),
DollarQuotedFunc: c.agent.HasFlag("dollar_quoted_func"),
Cache: c.agent.HasFlag("sql_cache"),
},
}),
}
return t
}
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)
}()
t.stats.Start()
appsec.Start()
return t
}
// Flush flushes any buffered traces. Flush is in effect only if a tracer
// is started. Users do not have to call Flush in order to ensure that
// traces reach Datadog. It is a convenience method dedicated to a specific
// use case described below.
//
// Flush is of use in Lambda environments, where starting and stopping
// the tracer on each invokation may create too much latency. In this
// scenario, a tracer may be started and stopped by the parent process
// whereas the invokation can make use of Flush to ensure any created spans
// reach the agent.
func Flush() {
if t, ok := internal.GetGlobalTracer().(*tracer); ok {
t.flushSync()
}
}
// flushSync triggers a flush and waits for it to complete.
func (t *tracer) flushSync() {
done := make(chan struct{})
t.flush <- done
<-done
}
// 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) {
for {
select {
case trace := <-t.out:
t.sampleFinishedTrace(trace)
if len(trace.spans) != 0 {
t.traceWriter.add(trace.spans)
}
case <-tick:
t.config.statsd.Incr("datadog.tracer.flush_triggered", []string{"reason:scheduled"}, 1)
t.traceWriter.flush()
case done := <-t.flush:
t.config.statsd.Incr("datadog.tracer.flush_triggered", []string{"reason:invoked"}, 1)
t.traceWriter.flush()
// TODO(x): In reality, the traceWriter.flush() call is not synchronous
// when using the agent traceWriter. However, this functionnality is used
// in Lambda so for that purpose this mechanism should suffice.
done <- struct{}{}
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.out:
t.sampleFinishedTrace(trace)
if len(trace.spans) != 0 {
t.traceWriter.add(trace.spans)
}
default:
break loop
}
}
return
}
}
}
// finishedTrace holds information about a trace that has finished, including its spans.
type finishedTrace struct {
spans []*span
decision samplingDecision
}
// sampleFinishedTrace applies single-span sampling to the provided trace, which is considered to be finished.
func (t *tracer) sampleFinishedTrace(info *finishedTrace) {
if info.decision == decisionKeep {
return
}
if !t.rulesSampling.HasSpanRules() {
info.spans = nil
return
}
// if trace sampling decision is drop, we still want to send single spans
// unless there are no single span sampling rules defined
var kept []*span
for _, span := range info.spans {
if t.rulesSampling.SampleSpan(span) {
kept = append(kept, span)
}
}
atomic.AddUint64(&t.droppedP0Spans, uint64(len(info.spans)-len(kept)))
info.spans = kept
if len(kept) == 0 {
atomic.AddUint64(&t.droppedP0Traces, 1)
return // no spans matched the rules and were sampled
}
atomic.AddUint64(&t.partialTraces, 1)
}
func (t *tracer) pushTrace(trace *finishedTrace) {
select {
case <-t.stop:
return
default:
}
select {
case t.out <- trace:
default:
log.Error("payload queue full, dropping %d traces", len(trace.spans))
}
}
// 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
// The default pprof context is taken from the start options and is
// not nil when using StartSpanFromContext()
pprofContext := opts.Context
if opts.Parent != nil {
if ctx, ok := opts.Parent.(*spanContext); ok {
context = ctx
if pprofContext == nil && ctx.span != nil {
// Inherit the context.Context from parent span if it was propagated
// using ChildOf() rather than StartSpanFromContext(), see
// applyPPROFLabels() below.
pprofContext = ctx.span.pprofCtxActive
}
}
}
if pprofContext == nil {
// For root span's without context, there is no pprofContext, but we need
// one to avoid a panic() in pprof.WithLabels(). Using context.Background()
// is not ideal here, as it will cause us to remove all labels from the
// goroutine when the span finishes. However, the alternatives of not
// applying labels for such spans or to leave the endpoint/hotspot labels
// on the goroutine after it finishes are even less appealing. We'll have
// to properly document this for users.
pprofContext = gocontext.Background()
}
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),
noDebugStack: t.config.noDebugStack,
}
if t.config.hostname != "" {
span.setMeta(keyHostname, t.config.hostname)
}
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 _, 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.serviceMappings != nil {
if newSvc, ok := t.config.serviceMappings[span.Service]; ok {
span.Service = newSvc
}
}
if context == nil || context.span == nil || context.span.Service != span.Service {
span.setMetric(keyTopLevel, 1)
// all top level spans are measured. So the measured tag is redundant.
delete(span.Metrics, keyMeasured)
}
if t.config.version != "" {
if t.config.universalVersion || (!t.config.universalVersion && span.Service == t.config.serviceName) {
span.setMeta(ext.Version, t.config.version)
}
}
if t.config.env != "" {
span.setMeta(ext.Environment, t.config.env)
}
if _, ok := span.context.samplingPriority(); !ok {
// if not already sampled or a brand new trace, sample it
t.sample(span)
}
if t.config.profilerHotspots || t.config.profilerEndpoints {
t.applyPPROFLabels(pprofContext, span)
}
if t.config.serviceMappings != nil {
if newSvc, ok := t.config.serviceMappings[span.Service]; ok {
span.Service = newSvc
}
}
if log.DebugEnabled() {
// avoid allocating the ...interface{} argument if debug logging is disabled
log.Debug("Started Span: %v, Operation: %s, Resource: %s, Tags: %v, %v",
span, span.Name, span.Resource, span.Meta, span.Metrics)
}
return span
}
// applyPPROFLabels applies pprof labels for the profiler's code hotspots and
// endpoint filtering feature to span. When span finishes, any pprof labels
// found in ctx are restored.
func (t *tracer) applyPPROFLabels(ctx gocontext.Context, span *span) {
var labels []string
if t.config.profilerHotspots {
labels = append(labels, traceprof.SpanID, strconv.FormatUint(span.SpanID, 10))
}
// nil checks might not be needed, but better be safe than sorry
if span.context.trace != nil && span.context.trace.root != nil {
localRootSpan := span.context.trace.root
if t.config.profilerHotspots {
labels = append(labels, traceprof.LocalRootSpanID, strconv.FormatUint(localRootSpan.SpanID, 10))
}
if t.config.profilerEndpoints && spanResourcePIISafe(localRootSpan) {
labels = append(labels, traceprof.TraceEndpoint, localRootSpan.Resource)
}
}
if len(labels) > 0 {
span.pprofCtxRestore = ctx
span.pprofCtxActive = pprof.WithLabels(ctx, pprof.Labels(labels...))
pprof.SetGoroutineLabels(span.pprofCtxActive)
}
}
// spanResourcePIISafe returns true if s.Resource can be considered to not
// include PII with reasonable confidence. E.g. SQL queries may contain PII,
// but http, rpc or custom (s.Type == "") span resource names generally do not.
func spanResourcePIISafe(s *span) bool {
return s.Type == ext.SpanTypeWeb || s.Type == ext.AppTypeRPC || s.Type == ""
}
// Stop stops the tracer.
func (t *tracer) Stop() {
t.stopOnce.Do(func() {
close(t.stop)
t.config.statsd.Incr("datadog.tracer.stopped", nil, 1)
})
t.stats.Stop()
t.wg.Wait()
t.traceWriter.stop()
t.config.statsd.Close()
appsec.Stop()
}
// 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)
}
// 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.trace.drop()
return
}
if rs, ok := sampler.(RateSampler); ok && rs.Rate() < 1 {
span.setMetric(sampleRateMetricKey, rs.Rate())
}
if t.rulesSampling.SampleTrace(span) {
return
}
t.prioritySampling.apply(span)
}
func startExecutionTracerTask(name string) func() {
if !rt.IsEnabled() {
return func() {}
}
_, task := rt.NewTask(gocontext.TODO(), name)
return task.End
}