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sampler_remote.go
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sampler_remote.go
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// Copyright The OpenTelemetry Authors
// Copyright (c) 2021 The Jaeger Authors.
// 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 jaegerremote // import "github.com/dillonstreator/opentelemetry-go-contrib/samplers/jaegerremote"
import (
"bytes"
"fmt"
"io"
"net/http"
"net/url"
"sync"
"sync/atomic"
"time"
"github.com/gogo/protobuf/jsonpb"
jaeger_api_v2 "github.com/dillonstreator/opentelemetry-go-contrib/samplers/jaegerremote/internal/proto-gen/jaeger-idl/proto/api_v2"
"go.opentelemetry.io/otel/sdk/trace"
)
const (
defaultRemoteSamplingTimeout = 10 * time.Second
defaultSamplingRefreshInterval = time.Minute
defaultSamplingMaxOperations = 256
defaultSamplingOperationNameLateBinding = true
)
// SamplingStrategyFetcher is used to fetch sampling strategy updates from remote server.
type SamplingStrategyFetcher interface {
Fetch(service string) ([]byte, error)
}
// samplingStrategyParser is used to parse sampling strategy updates. The output object
// should be of the type that is recognized by the SamplerUpdaters.
type samplingStrategyParser interface {
Parse(response []byte) (interface{}, error)
}
// samplerUpdater is used by Sampler to apply sampling strategies,
// retrieved from remote config server, to the current sampler. The updater can modify
// the sampler in-place if sampler supports it, or create a new one.
//
// If the strategy does not contain configuration for the sampler in question,
// updater must return modifiedSampler=nil to give other updaters a chance to inspect
// the sampling strategy response.
//
// Sampler invokes the updaters while holding a lock on the main sampler.
type samplerUpdater interface {
Update(sampler trace.Sampler, strategy interface{}) (modified trace.Sampler, err error)
}
// Sampler 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 Sampler 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 // used to serialize access to samplerConfig.sampler
config
serviceName string
doneChan chan *sync.WaitGroup
}
// New creates a sampler that periodically pulls
// the sampling strategy from an HTTP sampling server (e.g. jaeger-agent).
func New(
serviceName string,
opts ...Option,
) *Sampler {
options := newConfig(opts...)
sampler := &Sampler{
config: options,
serviceName: serviceName,
doneChan: make(chan *sync.WaitGroup),
}
go sampler.pollController()
return sampler
}
// ShouldSample returns a sampling choice based on the passed sampling
// parameters.
func (s *Sampler) ShouldSample(p trace.SamplingParameters) trace.SamplingResult {
s.RLock()
defer s.RUnlock()
return s.sampler.ShouldSample(p)
}
// Close does a clean shutdown of the sampler, stopping any background
// go-routines it may have started.
func (s *Sampler) Close() {
if swapped := atomic.CompareAndSwapInt64(&s.closed, 0, 1); !swapped {
s.logger.Info("repeated attempt to close the sampler is ignored")
return
}
var wg sync.WaitGroup
wg.Add(1)
s.doneChan <- &wg
wg.Wait()
}
// Description returns a human-readable name for the Sampler.
func (s *Sampler) Description() string {
return "JaegerRemoteSampler{}"
}
func (s *Sampler) pollController() {
ticker := time.NewTicker(s.samplingRefreshInterval)
defer ticker.Stop()
s.pollControllerWithTicker(ticker)
}
func (s *Sampler) pollControllerWithTicker(ticker *time.Ticker) {
s.UpdateSampler()
for {
select {
case <-ticker.C:
s.UpdateSampler()
case wg := <-s.doneChan:
wg.Done()
return
}
}
}
func (s *Sampler) setSampler(sampler trace.Sampler) {
s.Lock()
defer s.Unlock()
s.sampler = sampler
}
// UpdateSampler forces the sampler to fetch sampling strategy from backend server.
// This function is called automatically on a timer, but can also be safely called manually, e.g. from tests.
func (s *Sampler) UpdateSampler() {
res, err := s.samplingFetcher.Fetch(s.serviceName)
if err != nil {
s.logger.Error(err, "failed to fetch sampling strategy")
return
}
strategy, err := s.samplingParser.Parse(res)
if err != nil {
s.logger.Error(err, "failed to parse sampling strategy response")
return
}
s.Lock()
defer s.Unlock()
if err := s.updateSamplerViaUpdaters(strategy); err != nil {
s.logger.Error(err, "failed to handle sampling strategy response", "response", res)
return
}
}
// NB: this function should only be called while holding a Write lock.
func (s *Sampler) updateSamplerViaUpdaters(strategy interface{}) error {
for _, updater := range s.updaters {
sampler, err := updater.Update(s.sampler, strategy)
if err != nil {
return err
}
if sampler != nil {
s.sampler = sampler
return nil
}
}
return fmt.Errorf("unsupported sampling strategy %+v", strategy)
}
// -----------------------
// probabilisticSamplerUpdater is used by Sampler to parse sampling configuration.
type probabilisticSamplerUpdater struct{}
// Update implements Update of samplerUpdater.
func (u *probabilisticSamplerUpdater) Update(sampler trace.Sampler, strategy interface{}) (trace.Sampler, error) {
type response interface {
GetProbabilisticSampling() *jaeger_api_v2.ProbabilisticSamplingStrategy
}
var _ response = new(jaeger_api_v2.SamplingStrategyResponse) // sanity signature check
if resp, ok := strategy.(response); ok {
if probabilistic := resp.GetProbabilisticSampling(); probabilistic != nil {
if ps, ok := sampler.(*probabilisticSampler); ok {
if err := ps.Update(probabilistic.SamplingRate); err != nil {
return nil, err
}
return sampler, nil
}
return newProbabilisticSampler(probabilistic.SamplingRate), nil
}
}
return nil, nil
}
// -----------------------
// rateLimitingSamplerUpdater is used by Sampler to parse sampling configuration.
type rateLimitingSamplerUpdater struct{}
// Update implements Update of samplerUpdater.
func (u *rateLimitingSamplerUpdater) Update(sampler trace.Sampler, strategy interface{}) (trace.Sampler, error) {
type response interface {
GetRateLimitingSampling() *jaeger_api_v2.RateLimitingSamplingStrategy
}
var _ response = new(jaeger_api_v2.SamplingStrategyResponse) // sanity signature check
if resp, ok := strategy.(response); ok {
if rateLimiting := resp.GetRateLimitingSampling(); rateLimiting != nil {
rateLimit := float64(rateLimiting.MaxTracesPerSecond)
if rl, ok := sampler.(*rateLimitingSampler); ok {
rl.Update(rateLimit)
return rl, nil
}
return newRateLimitingSampler(rateLimit), nil
}
}
return nil, nil
}
// -----------------------
// perOperationSamplerUpdater is used by Sampler to parse sampling configuration.
// Fields have the same meaning as in perOperationSamplerParams.
type perOperationSamplerUpdater struct {
MaxOperations int
OperationNameLateBinding bool
}
// Update implements Update of samplerUpdater.
func (u *perOperationSamplerUpdater) Update(sampler trace.Sampler, strategy interface{}) (trace.Sampler, error) {
type response interface {
GetOperationSampling() *jaeger_api_v2.PerOperationSamplingStrategies
}
var _ response = new(jaeger_api_v2.SamplingStrategyResponse) // sanity signature check
if p, ok := strategy.(response); ok {
if operations := p.GetOperationSampling(); operations != nil {
if as, ok := sampler.(*perOperationSampler); ok {
as.update(operations)
return as, nil
}
return newPerOperationSampler(perOperationSamplerParams{
MaxOperations: u.MaxOperations,
OperationNameLateBinding: u.OperationNameLateBinding,
Strategies: operations,
}), nil
}
}
return nil, nil
}
// -----------------------
type httpSamplingStrategyFetcher struct {
serverURL string
httpClient http.Client
}
func newHTTPSamplingStrategyFetcher(serverURL string) *httpSamplingStrategyFetcher {
return &httpSamplingStrategyFetcher{
serverURL: serverURL,
httpClient: http.Client{
Timeout: defaultRemoteSamplingTimeout,
},
}
}
func (f *httpSamplingStrategyFetcher) Fetch(serviceName string) ([]byte, error) {
v := url.Values{}
v.Set("service", serviceName)
uri := f.serverURL + "?" + v.Encode()
resp, err := f.httpClient.Get(uri)
if err != nil {
return nil, err
}
defer resp.Body.Close()
body, err := io.ReadAll(resp.Body)
if err != nil {
return nil, err
}
if resp.StatusCode >= 400 {
return nil, fmt.Errorf("status code: %d, body: %c", resp.StatusCode, body)
}
return body, nil
}
// -----------------------
type samplingStrategyParserImpl struct{}
func (p *samplingStrategyParserImpl) Parse(response []byte) (interface{}, error) {
strategy := new(jaeger_api_v2.SamplingStrategyResponse)
// Official Jaeger Remote Sampling protocol contains enums encoded as strings.
// Legacy protocol contains enums as numbers.
// Gogo's jsonpb module can parse either format.
// Cf. https://github.com/open-telemetry/opentelemetry-go-contrib/issues/3184
if err := jsonpb.Unmarshal(bytes.NewReader(response), strategy); err != nil {
return nil, err
}
return strategy, nil
}