summaryrefslogtreecommitdiff
path: root/vendor/github.com/uber/jaeger-client-go/sampler.go
blob: ea6984e02b9d87a5fd224e511fecb6c925286901 (plain)
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
// Copyright (c) 2017 Uber Technologies, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package jaeger

import (
	"fmt"
	"math"
	"net/url"
	"sync"
	"sync/atomic"
	"time"

	"github.com/uber/jaeger-client-go/log"
	"github.com/uber/jaeger-client-go/thrift-gen/sampling"
	"github.com/uber/jaeger-client-go/utils"
)

const (
	defaultSamplingRefreshInterval = time.Minute
	defaultMaxOperations           = 2000
)

// Sampler decides whether a new trace should be sampled or not.
type Sampler interface {
	// IsSampled decides whether a trace with given `id` and `operation`
	// should be sampled. This function will also return the tags that
	// can be used to identify the type of sampling that was applied to
	// the root span. Most simple samplers would return two tags,
	// sampler.type and sampler.param, similar to those used in the Configuration
	IsSampled(id TraceID, operation string) (sampled bool, tags []Tag)

	// Close does a clean shutdown of the sampler, stopping any background
	// go-routines it may have started.
	Close()

	// Equal checks if the `other` sampler is functionally equivalent
	// to this sampler.
	// TODO remove this function. This function is used to determine if 2 samplers are equivalent
	// which does not bode well with the adaptive sampler which has to create all the composite samplers
	// for the comparison to occur. This is expensive to do if only one sampler has changed.
	Equal(other Sampler) bool
}

// -----------------------

// ConstSampler is a sampler that always makes the same decision.
type ConstSampler struct {
	Decision bool
	tags     []Tag
}

// NewConstSampler creates a ConstSampler.
func NewConstSampler(sample bool) Sampler {
	tags := []Tag{
		{key: SamplerTypeTagKey, value: SamplerTypeConst},
		{key: SamplerParamTagKey, value: sample},
	}
	return &ConstSampler{Decision: sample, tags: tags}
}

// IsSampled implements IsSampled() of Sampler.
func (s *ConstSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
	return s.Decision, s.tags
}

// Close implements Close() of Sampler.
func (s *ConstSampler) Close() {
	// nothing to do
}

// Equal implements Equal() of Sampler.
func (s *ConstSampler) Equal(other Sampler) bool {
	if o, ok := other.(*ConstSampler); ok {
		return s.Decision == o.Decision
	}
	return false
}

// -----------------------

// ProbabilisticSampler is a sampler that randomly samples a certain percentage
// of traces.
type ProbabilisticSampler struct {
	samplingRate     float64
	samplingBoundary uint64
	tags             []Tag
}

const maxRandomNumber = ^(uint64(1) << 63) // i.e. 0x7fffffffffffffff

// NewProbabilisticSampler creates a sampler that randomly samples a certain percentage of traces specified by the
// samplingRate, in the range between 0.0 and 1.0.
//
// It relies on the fact that new trace IDs are 63bit random numbers themselves, thus making the sampling decision
// without generating a new random number, but simply calculating if traceID < (samplingRate * 2^63).
// TODO remove the error from this function for next major release
func NewProbabilisticSampler(samplingRate float64) (*ProbabilisticSampler, error) {
	if samplingRate < 0.0 || samplingRate > 1.0 {
		return nil, fmt.Errorf("Sampling Rate must be between 0.0 and 1.0, received %f", samplingRate)
	}
	return newProbabilisticSampler(samplingRate), nil
}

func newProbabilisticSampler(samplingRate float64) *ProbabilisticSampler {
	samplingRate = math.Max(0.0, math.Min(samplingRate, 1.0))
	tags := []Tag{
		{key: SamplerTypeTagKey, value: SamplerTypeProbabilistic},
		{key: SamplerParamTagKey, value: samplingRate},
	}
	return &ProbabilisticSampler{
		samplingRate:     samplingRate,
		samplingBoundary: uint64(float64(maxRandomNumber) * samplingRate),
		tags:             tags,
	}
}

// SamplingRate returns the sampling probability this sampled was constructed with.
func (s *ProbabilisticSampler) SamplingRate() float64 {
	return s.samplingRate
}

// IsSampled implements IsSampled() of Sampler.
func (s *ProbabilisticSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
	return s.samplingBoundary >= id.Low, s.tags
}

// Close implements Close() of Sampler.
func (s *ProbabilisticSampler) Close() {
	// nothing to do
}

// Equal implements Equal() of Sampler.
func (s *ProbabilisticSampler) Equal(other Sampler) bool {
	if o, ok := other.(*ProbabilisticSampler); ok {
		return s.samplingBoundary == o.samplingBoundary
	}
	return false
}

// -----------------------

type rateLimitingSampler struct {
	maxTracesPerSecond float64
	rateLimiter        utils.RateLimiter
	tags               []Tag
}

// NewRateLimitingSampler creates a sampler that samples at most maxTracesPerSecond. The distribution of sampled
// traces follows burstiness of the service, i.e. a service with uniformly distributed requests will have those
// requests sampled uniformly as well, but if requests are bursty, especially sub-second, then a number of
// sequential requests can be sampled each second.
func NewRateLimitingSampler(maxTracesPerSecond float64) Sampler {
	tags := []Tag{
		{key: SamplerTypeTagKey, value: SamplerTypeRateLimiting},
		{key: SamplerParamTagKey, value: maxTracesPerSecond},
	}
	return &rateLimitingSampler{
		maxTracesPerSecond: maxTracesPerSecond,
		rateLimiter:        utils.NewRateLimiter(maxTracesPerSecond, math.Max(maxTracesPerSecond, 1.0)),
		tags:               tags,
	}
}

// IsSampled implements IsSampled() of Sampler.
func (s *rateLimitingSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
	return s.rateLimiter.CheckCredit(1.0), s.tags
}

func (s *rateLimitingSampler) Close() {
	// nothing to do
}

func (s *rateLimitingSampler) Equal(other Sampler) bool {
	if o, ok := other.(*rateLimitingSampler); ok {
		return s.maxTracesPerSecond == o.maxTracesPerSecond
	}
	return false
}

// -----------------------

// GuaranteedThroughputProbabilisticSampler is a sampler that leverages both probabilisticSampler and
// rateLimitingSampler. The rateLimitingSampler is used as a guaranteed lower bound sampler such that
// every operation is sampled at least once in a time interval defined by the lowerBound. ie a lowerBound
// of 1.0 / (60 * 10) will sample an operation at least once every 10 minutes.
//
// The probabilisticSampler is given higher priority when tags are emitted, ie. if IsSampled() for both
// samplers return true, the tags for probabilisticSampler will be used.
type GuaranteedThroughputProbabilisticSampler struct {
	probabilisticSampler *ProbabilisticSampler
	lowerBoundSampler    Sampler
	tags                 []Tag
	samplingRate         float64
	lowerBound           float64
}

// NewGuaranteedThroughputProbabilisticSampler returns a delegating sampler that applies both
// probabilisticSampler and rateLimitingSampler.
func NewGuaranteedThroughputProbabilisticSampler(
	lowerBound, samplingRate float64,
) (*GuaranteedThroughputProbabilisticSampler, error) {
	return newGuaranteedThroughputProbabilisticSampler(lowerBound, samplingRate), nil
}

func newGuaranteedThroughputProbabilisticSampler(lowerBound, samplingRate float64) *GuaranteedThroughputProbabilisticSampler {
	s := &GuaranteedThroughputProbabilisticSampler{
		lowerBoundSampler: NewRateLimitingSampler(lowerBound),
		lowerBound:        lowerBound,
	}
	s.setProbabilisticSampler(samplingRate)
	return s
}

func (s *GuaranteedThroughputProbabilisticSampler) setProbabilisticSampler(samplingRate float64) {
	if s.probabilisticSampler == nil || s.samplingRate != samplingRate {
		s.probabilisticSampler = newProbabilisticSampler(samplingRate)
		s.samplingRate = s.probabilisticSampler.SamplingRate()
		s.tags = []Tag{
			{key: SamplerTypeTagKey, value: SamplerTypeLowerBound},
			{key: SamplerParamTagKey, value: s.samplingRate},
		}
	}
}

// IsSampled implements IsSampled() of Sampler.
func (s *GuaranteedThroughputProbabilisticSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
	if sampled, tags := s.probabilisticSampler.IsSampled(id, operation); sampled {
		s.lowerBoundSampler.IsSampled(id, operation)
		return true, tags
	}
	sampled, _ := s.lowerBoundSampler.IsSampled(id, operation)
	return sampled, s.tags
}

// Close implements Close() of Sampler.
func (s *GuaranteedThroughputProbabilisticSampler) Close() {
	s.probabilisticSampler.Close()
	s.lowerBoundSampler.Close()
}

// Equal implements Equal() of Sampler.
func (s *GuaranteedThroughputProbabilisticSampler) Equal(other Sampler) bool {
	// NB The Equal() function is expensive and will be removed. See adaptiveSampler.Equal() for
	// more information.
	return false
}

// this function should only be called while holding a Write lock
func (s *GuaranteedThroughputProbabilisticSampler) update(lowerBound, samplingRate float64) {
	s.setProbabilisticSampler(samplingRate)
	if s.lowerBound != lowerBound {
		s.lowerBoundSampler = NewRateLimitingSampler(lowerBound)
		s.lowerBound = lowerBound
	}
}

// -----------------------

type adaptiveSampler struct {
	sync.RWMutex

	samplers       map[string]*GuaranteedThroughputProbabilisticSampler
	defaultSampler *ProbabilisticSampler
	lowerBound     float64
	maxOperations  int
}

// NewAdaptiveSampler returns a delegating sampler that applies both probabilisticSampler and
// rateLimitingSampler via the guaranteedThroughputProbabilisticSampler. This sampler keeps track of all
// operations and delegates calls to the respective guaranteedThroughputProbabilisticSampler.
func NewAdaptiveSampler(strategies *sampling.PerOperationSamplingStrategies, maxOperations int) (Sampler, error) {
	return newAdaptiveSampler(strategies, maxOperations), nil
}

func newAdaptiveSampler(strategies *sampling.PerOperationSamplingStrategies, maxOperations int) Sampler {
	samplers := make(map[string]*GuaranteedThroughputProbabilisticSampler)
	for _, strategy := range strategies.PerOperationStrategies {
		sampler := newGuaranteedThroughputProbabilisticSampler(
			strategies.DefaultLowerBoundTracesPerSecond,
			strategy.ProbabilisticSampling.SamplingRate,
		)
		samplers[strategy.Operation] = sampler
	}
	return &adaptiveSampler{
		samplers:       samplers,
		defaultSampler: newProbabilisticSampler(strategies.DefaultSamplingProbability),
		lowerBound:     strategies.DefaultLowerBoundTracesPerSecond,
		maxOperations:  maxOperations,
	}
}

func (s *adaptiveSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
	s.RLock()
	sampler, ok := s.samplers[operation]
	if ok {
		defer s.RUnlock()
		return sampler.IsSampled(id, operation)
	}
	s.RUnlock()
	s.Lock()
	defer s.Unlock()

	// Check if sampler has already been created
	sampler, ok = s.samplers[operation]
	if ok {
		return sampler.IsSampled(id, operation)
	}
	// Store only up to maxOperations of unique ops.
	if len(s.samplers) >= s.maxOperations {
		return s.defaultSampler.IsSampled(id, operation)
	}
	newSampler := newGuaranteedThroughputProbabilisticSampler(s.lowerBound, s.defaultSampler.SamplingRate())
	s.samplers[operation] = newSampler
	return newSampler.IsSampled(id, operation)
}

func (s *adaptiveSampler) Close() {
	s.Lock()
	defer s.Unlock()
	for _, sampler := range s.samplers {
		sampler.Close()
	}
	s.defaultSampler.Close()
}

func (s *adaptiveSampler) Equal(other Sampler) bool {
	// NB The Equal() function is overly expensive for adaptiveSampler since it's composed of multiple
	// samplers which all need to be initialized before this function can be called for a comparison.
	// Therefore, adaptiveSampler uses the update() function to only alter the samplers that need
	// changing. Hence this function always returns false so that the update function can be called.
	// Once the Equal() function is removed from the Sampler API, this will no longer be needed.
	return false
}

func (s *adaptiveSampler) update(strategies *sampling.PerOperationSamplingStrategies) {
	s.Lock()
	defer s.Unlock()
	newSamplers := map[string]*GuaranteedThroughputProbabilisticSampler{}
	for _, strategy := range strategies.PerOperationStrategies {
		operation := strategy.Operation
		samplingRate := strategy.ProbabilisticSampling.SamplingRate
		lowerBound := strategies.DefaultLowerBoundTracesPerSecond
		if sampler, ok := s.samplers[operation]; ok {
			sampler.update(lowerBound, samplingRate)
			newSamplers[operation] = sampler
		} else {
			sampler := newGuaranteedThroughputProbabilisticSampler(
				lowerBound,
				samplingRate,
			)
			newSamplers[operation] = sampler
		}
	}
	s.lowerBound = strategies.DefaultLowerBoundTracesPerSecond
	if s.defaultSampler.SamplingRate() != strategies.DefaultSamplingProbability {
		s.defaultSampler = newProbabilisticSampler(strategies.DefaultSamplingProbability)
	}
	s.samplers = newSamplers
}

// -----------------------

// RemotelyControlledSampler is a delegating sampler that polls a remote server
// for the appropriate sampling strategy, constructs a corresponding sampler and
// delegates to it for sampling decisions.
type RemotelyControlledSampler struct {
	// These fields must be first in the struct because `sync/atomic` expects 64-bit alignment.
	// Cf. https://github.com/uber/jaeger-client-go/issues/155, https://goo.gl/zW7dgq
	closed int64 // 0 - not closed, 1 - closed

	sync.RWMutex
	samplerOptions

	serviceName string
	manager     sampling.SamplingManager
	doneChan    chan *sync.WaitGroup
}

type httpSamplingManager struct {
	serverURL string
}

func (s *httpSamplingManager) GetSamplingStrategy(serviceName string) (*sampling.SamplingStrategyResponse, error) {
	var out sampling.SamplingStrategyResponse
	v := url.Values{}
	v.Set("service", serviceName)
	if err := utils.GetJSON(s.serverURL+"?"+v.Encode(), &out); err != nil {
		return nil, err
	}
	return &out, nil
}

// NewRemotelyControlledSampler creates a sampler that periodically pulls
// the sampling strategy from an HTTP sampling server (e.g. jaeger-agent).
func NewRemotelyControlledSampler(
	serviceName string,
	opts ...SamplerOption,
) *RemotelyControlledSampler {
	options := applySamplerOptions(opts...)
	sampler := &RemotelyControlledSampler{
		samplerOptions: options,
		serviceName:    serviceName,
		manager:        &httpSamplingManager{serverURL: options.samplingServerURL},
		doneChan:       make(chan *sync.WaitGroup),
	}
	go sampler.pollController()
	return sampler
}

func applySamplerOptions(opts ...SamplerOption) samplerOptions {
	options := samplerOptions{}
	for _, option := range opts {
		option(&options)
	}
	if options.sampler == nil {
		options.sampler = newProbabilisticSampler(0.001)
	}
	if options.logger == nil {
		options.logger = log.NullLogger
	}
	if options.maxOperations <= 0 {
		options.maxOperations = defaultMaxOperations
	}
	if options.samplingServerURL == "" {
		options.samplingServerURL = DefaultSamplingServerURL
	}
	if options.metrics == nil {
		options.metrics = NewNullMetrics()
	}
	if options.samplingRefreshInterval <= 0 {
		options.samplingRefreshInterval = defaultSamplingRefreshInterval
	}
	return options
}

// IsSampled implements IsSampled() of Sampler.
func (s *RemotelyControlledSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
	s.RLock()
	defer s.RUnlock()
	return s.sampler.IsSampled(id, operation)
}

// Close implements Close() of Sampler.
func (s *RemotelyControlledSampler) Close() {
	if swapped := atomic.CompareAndSwapInt64(&s.closed, 0, 1); !swapped {
		s.logger.Error("Repeated attempt to close the sampler is ignored")
		return
	}

	var wg sync.WaitGroup
	wg.Add(1)
	s.doneChan <- &wg
	wg.Wait()
}

// Equal implements Equal() of Sampler.
func (s *RemotelyControlledSampler) Equal(other Sampler) bool {
	// NB The Equal() function is expensive and will be removed. See adaptiveSampler.Equal() for
	// more information.
	if o, ok := other.(*RemotelyControlledSampler); ok {
		s.RLock()
		o.RLock()
		defer s.RUnlock()
		defer o.RUnlock()
		return s.sampler.Equal(o.sampler)
	}
	return false
}

func (s *RemotelyControlledSampler) pollController() {
	ticker := time.NewTicker(s.samplingRefreshInterval)
	defer ticker.Stop()
	s.pollControllerWithTicker(ticker)
}

func (s *RemotelyControlledSampler) pollControllerWithTicker(ticker *time.Ticker) {
	for {
		select {
		case <-ticker.C:
			s.updateSampler()
		case wg := <-s.doneChan:
			wg.Done()
			return
		}
	}
}

func (s *RemotelyControlledSampler) getSampler() Sampler {
	s.Lock()
	defer s.Unlock()
	return s.sampler
}

func (s *RemotelyControlledSampler) setSampler(sampler Sampler) {
	s.Lock()
	defer s.Unlock()
	s.sampler = sampler
}

func (s *RemotelyControlledSampler) updateSampler() {
	res, err := s.manager.GetSamplingStrategy(s.serviceName)
	if err != nil {
		s.metrics.SamplerQueryFailure.Inc(1)
		s.logger.Infof("Unable to query sampling strategy: %v", err)
		return
	}
	s.Lock()
	defer s.Unlock()

	s.metrics.SamplerRetrieved.Inc(1)
	if strategies := res.GetOperationSampling(); strategies != nil {
		s.updateAdaptiveSampler(strategies)
	} else {
		err = s.updateRateLimitingOrProbabilisticSampler(res)
	}
	if err != nil {
		s.metrics.SamplerUpdateFailure.Inc(1)
		s.logger.Infof("Unable to handle sampling strategy response %+v. Got error: %v", res, err)
		return
	}
	s.metrics.SamplerUpdated.Inc(1)
}

// NB: this function should only be called while holding a Write lock
func (s *RemotelyControlledSampler) updateAdaptiveSampler(strategies *sampling.PerOperationSamplingStrategies) {
	if adaptiveSampler, ok := s.sampler.(*adaptiveSampler); ok {
		adaptiveSampler.update(strategies)
	} else {
		s.sampler = newAdaptiveSampler(strategies, s.maxOperations)
	}
}

// NB: this function should only be called while holding a Write lock
func (s *RemotelyControlledSampler) updateRateLimitingOrProbabilisticSampler(res *sampling.SamplingStrategyResponse) error {
	var newSampler Sampler
	if probabilistic := res.GetProbabilisticSampling(); probabilistic != nil {
		newSampler = newProbabilisticSampler(probabilistic.SamplingRate)
	} else if rateLimiting := res.GetRateLimitingSampling(); rateLimiting != nil {
		newSampler = NewRateLimitingSampler(float64(rateLimiting.MaxTracesPerSecond))
	} else {
		return fmt.Errorf("Unsupported sampling strategy type %v", res.GetStrategyType())
	}
	if !s.sampler.Equal(newSampler) {
		s.sampler = newSampler
	}
	return nil
}