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// 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 (
"encoding/json"
"fmt"
"io/ioutil"
"net/http"
"net/url"
"sync"
"sync/atomic"
"time"
"github.com/uber/jaeger-client-go/log"
"github.com/uber/jaeger-client-go/thrift-gen/sampling"
)
const (
defaultRemoteSamplingTimeout = 10 * time.Second
defaultSamplingRefreshInterval = time.Minute
)
// 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 RemotelyControlledSampler 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.
//
// RemotelyControlledSampler invokes the updaters while holding a lock on the main sampler.
type SamplerUpdater interface {
Update(sampler SamplerV2, strategy interface{}) (modified SamplerV2, err error)
}
// 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 // used to serialize access to samplerOptions.sampler
samplerOptions
serviceName string
doneChan chan *sync.WaitGroup
}
// 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 := new(samplerOptions).applyOptionsAndDefaults(opts...)
sampler := &RemotelyControlledSampler{
samplerOptions: *options,
serviceName: serviceName,
doneChan: make(chan *sync.WaitGroup),
}
go sampler.pollController()
return sampler
}
// IsSampled implements IsSampled() of Sampler.
// TODO (breaking change) remove when Sampler V1 is removed
func (s *RemotelyControlledSampler) IsSampled(id TraceID, operation string) (bool, []Tag) {
return false, nil
}
// OnCreateSpan implements OnCreateSpan of SamplerV2.
func (s *RemotelyControlledSampler) OnCreateSpan(span *Span) SamplingDecision {
s.RLock()
defer s.RUnlock()
return s.sampler.OnCreateSpan(span)
}
// OnSetOperationName implements OnSetOperationName of SamplerV2.
func (s *RemotelyControlledSampler) OnSetOperationName(span *Span, operationName string) SamplingDecision {
s.RLock()
defer s.RUnlock()
return s.sampler.OnSetOperationName(span, operationName)
}
// OnSetTag implements OnSetTag of SamplerV2.
func (s *RemotelyControlledSampler) OnSetTag(span *Span, key string, value interface{}) SamplingDecision {
s.RLock()
defer s.RUnlock()
return s.sampler.OnSetTag(span, key, value)
}
// OnFinishSpan implements OnFinishSpan of SamplerV2.
func (s *RemotelyControlledSampler) OnFinishSpan(span *Span) SamplingDecision {
s.RLock()
defer s.RUnlock()
return s.sampler.OnFinishSpan(span)
}
// 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 PerOperationSampler.Equal() for
// more information.
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
}
}
}
// Sampler returns the currently active sampler.
func (s *RemotelyControlledSampler) Sampler() SamplerV2 {
s.RLock()
defer s.RUnlock()
return s.sampler
}
func (s *RemotelyControlledSampler) setSampler(sampler SamplerV2) {
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 *RemotelyControlledSampler) UpdateSampler() {
res, err := s.samplingFetcher.Fetch(s.serviceName)
if err != nil {
s.metrics.SamplerQueryFailure.Inc(1)
s.logger.Infof("failed to fetch sampling strategy: %v", err)
return
}
strategy, err := s.samplingParser.Parse(res)
if err != nil {
s.metrics.SamplerUpdateFailure.Inc(1)
s.logger.Infof("failed to parse sampling strategy response: %v", err)
return
}
s.Lock()
defer s.Unlock()
s.metrics.SamplerRetrieved.Inc(1)
if err := s.updateSamplerViaUpdaters(strategy); err != nil {
s.metrics.SamplerUpdateFailure.Inc(1)
s.logger.Infof("failed 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) 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.logger.Debugf("sampler updated: %+v", sampler)
s.sampler = sampler
return nil
}
}
return fmt.Errorf("unsupported sampling strategy %+v", strategy)
}
// -----------------------
// ProbabilisticSamplerUpdater is used by RemotelyControlledSampler to parse sampling configuration.
type ProbabilisticSamplerUpdater struct{}
// Update implements Update of SamplerUpdater.
func (u *ProbabilisticSamplerUpdater) Update(sampler SamplerV2, strategy interface{}) (SamplerV2, error) {
type response interface {
GetProbabilisticSampling() *sampling.ProbabilisticSamplingStrategy
}
var _ response = new(sampling.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 RemotelyControlledSampler to parse sampling configuration.
type RateLimitingSamplerUpdater struct{}
// Update implements Update of SamplerUpdater.
func (u *RateLimitingSamplerUpdater) Update(sampler SamplerV2, strategy interface{}) (SamplerV2, error) {
type response interface {
GetRateLimitingSampling() *sampling.RateLimitingSamplingStrategy
}
var _ response = new(sampling.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
}
// -----------------------
// AdaptiveSamplerUpdater is used by RemotelyControlledSampler to parse sampling configuration.
// Fields have the same meaning as in PerOperationSamplerParams.
type AdaptiveSamplerUpdater struct {
MaxOperations int
OperationNameLateBinding bool
}
// Update implements Update of SamplerUpdater.
func (u *AdaptiveSamplerUpdater) Update(sampler SamplerV2, strategy interface{}) (SamplerV2, error) {
type response interface {
GetOperationSampling() *sampling.PerOperationSamplingStrategies
}
var _ response = new(sampling.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
logger log.DebugLogger
httpClient http.Client
}
func newHTTPSamplingStrategyFetcher(serverURL string, logger log.DebugLogger) *httpSamplingStrategyFetcher {
customTransport := http.DefaultTransport.(*http.Transport).Clone()
customTransport.ResponseHeaderTimeout = defaultRemoteSamplingTimeout
return &httpSamplingStrategyFetcher{
serverURL: serverURL,
logger: logger,
httpClient: http.Client{
Transport: customTransport,
},
}
}
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 func() {
if err := resp.Body.Close(); err != nil {
f.logger.Error(fmt.Sprintf("failed to close HTTP response body: %+v", err))
}
}()
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, err
}
if resp.StatusCode >= 400 {
return nil, fmt.Errorf("StatusCode: %d, Body: %s", resp.StatusCode, body)
}
return body, nil
}
// -----------------------
type samplingStrategyParser struct{}
func (p *samplingStrategyParser) Parse(response []byte) (interface{}, error) {
strategy := new(sampling.SamplingStrategyResponse)
if err := json.Unmarshal(response, strategy); err != nil {
return nil, err
}
return strategy, nil
}