/
rules_sampler.go
593 lines (540 loc) · 19.8 KB
/
rules_sampler.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 Datadog, Inc.
package tracer
import (
"encoding/json"
"fmt"
"math"
"os"
"regexp"
"strconv"
"strings"
"sync"
"time"
"golang.org/x/time/rate"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
"gopkg.in/DataDog/dd-trace-go.v1/internal/log"
"gopkg.in/DataDog/dd-trace-go.v1/internal/samplernames"
)
// rulesSampler holds instances of trace sampler and single span sampler, that are configured with the given set of rules.
type rulesSampler struct {
// traceRulesSampler samples trace spans based on a user-defined set of rules and might impact sampling decision of the trace.
traces *traceRulesSampler
// singleSpanRulesSampler samples individual spans based on a separate user-defined set of rules and
// cannot impact the trace sampling decision.
spans *singleSpanRulesSampler
}
// newRulesSampler configures a *rulesSampler instance using the given set of rules.
// Rules are split between trace and single span sampling rules according to their type.
// Such rules are user-defined through environment variable or WithSamplingRules option.
// Invalid rules or environment variable values are tolerated, by logging warnings and then ignoring them.
func newRulesSampler(traceRules, spanRules []SamplingRule) *rulesSampler {
return &rulesSampler{
traces: newTraceRulesSampler(traceRules),
spans: newSingleSpanRulesSampler(spanRules),
}
}
func (r *rulesSampler) SampleTrace(s *span) bool { return r.traces.apply(s) }
func (r *rulesSampler) SampleSpan(s *span) bool { return r.spans.apply(s) }
func (r *rulesSampler) HasSpanRules() bool { return r.spans.enabled() }
func (r *rulesSampler) TraceRateLimit() (float64, bool) { return r.traces.limit() }
// SamplingRule is used for applying sampling rates to spans that match
// the service name, operation name or both.
// For basic usage, consider using the helper functions ServiceRule, NameRule, etc.
type SamplingRule struct {
// Service specifies the regex pattern that a span service name must match.
Service *regexp.Regexp
// Name specifies the regex pattern that a span operation name must match.
Name *regexp.Regexp
// Rate specifies the sampling rate that should be applied to spans that match
// service and/or name of the rule.
Rate float64
// MaxPerSecond specifies max number of spans per second that can be sampled per the rule.
// If not specified, the default is no limit.
MaxPerSecond float64
ruleType SamplingRuleType
exactService string
exactName string
limiter *rateLimiter
}
// match returns true when the span's details match all the expected values in the rule.
func (sr *SamplingRule) match(s *span) bool {
if sr.Service != nil && !sr.Service.MatchString(s.Service) {
return false
} else if sr.exactService != "" && sr.exactService != s.Service {
return false
}
if sr.Name != nil && !sr.Name.MatchString(s.Name) {
return false
} else if sr.exactName != "" && sr.exactName != s.Name {
return false
}
return true
}
// SamplingRuleType represents a type of sampling rule spans are matched against.
type SamplingRuleType int
const (
// SamplingRuleTrace specifies a sampling rule that applies to the entire trace if any spans satisfy the criteria.
// If a sampling rule is of type SamplingRuleTrace, such rule determines the sampling rate to apply
// to trace spans. If a span matches that rule, it will impact the trace sampling decision.
SamplingRuleTrace = iota
// SamplingRuleSpan specifies a sampling rule that applies to a single span without affecting the entire trace.
// If a sampling rule is of type SamplingRuleSingleSpan, such rule determines the sampling rate to apply
// to individual spans. If a span matches a rule, it will NOT impact the trace sampling decision.
// In the case that a trace is dropped and thus not sent to the Agent, spans kept on account
// of matching SamplingRuleSingleSpan rules must be conveyed separately.
SamplingRuleSpan
)
func (sr SamplingRuleType) String() string {
switch sr {
case SamplingRuleTrace:
return "trace"
case SamplingRuleSpan:
return "span"
default:
return ""
}
}
// ServiceRule returns a SamplingRule that applies the provided sampling rate
// to spans that match the service name provided.
func ServiceRule(service string, rate float64) SamplingRule {
return SamplingRule{
exactService: service,
Rate: rate,
}
}
// NameRule returns a SamplingRule that applies the provided sampling rate
// to spans that match the operation name provided.
func NameRule(name string, rate float64) SamplingRule {
return SamplingRule{
exactName: name,
Rate: rate,
}
}
// NameServiceRule returns a SamplingRule that applies the provided sampling rate
// to spans matching both the operation and service names provided.
func NameServiceRule(name string, service string, rate float64) SamplingRule {
return SamplingRule{
exactService: service,
exactName: name,
Rate: rate,
}
}
// RateRule returns a SamplingRule that applies the provided sampling rate to all spans.
func RateRule(rate float64) SamplingRule {
return SamplingRule{
Rate: rate,
}
}
// SpanNameServiceRule returns a SamplingRule of type SamplingRuleSpan that applies
// the provided sampling rate to all spans matching the operation and service name glob patterns provided.
// Operation and service fields must be valid glob patterns.
func SpanNameServiceRule(name, service string, rate float64) SamplingRule {
return SamplingRule{
Service: globMatch(service),
Name: globMatch(name),
Rate: rate,
ruleType: SamplingRuleSpan,
exactName: name,
limiter: newSingleSpanRateLimiter(0),
}
}
// SpanNameServiceMPSRule returns a SamplingRule of type SamplingRuleSpan that applies
// the provided sampling rate to all spans matching the operation and service name glob patterns
// up to the max number of spans per second that can be sampled.
// Operation and service fields must be valid glob patterns.
func SpanNameServiceMPSRule(name, service string, rate, limit float64) SamplingRule {
return SamplingRule{
Service: globMatch(service),
Name: globMatch(name),
MaxPerSecond: limit,
Rate: rate,
ruleType: SamplingRuleSpan,
exactName: name,
limiter: newSingleSpanRateLimiter(limit),
}
}
// traceRulesSampler allows a user-defined list of rules to apply to traces.
// These rules can match based on the span's Service, Name or both.
// When making a sampling decision, the rules are checked in order until
// a match is found.
// If a match is found, the rate from that rule is used.
// If no match is found, and the DD_TRACE_SAMPLE_RATE environment variable
// was set to a valid rate, that value is used.
// Otherwise, the rules sampler didn't apply to the span, and the decision
// is passed to the priority sampler.
//
// The rate is used to determine if the span should be sampled, but an upper
// limit can be defined using the DD_TRACE_RATE_LIMIT environment variable.
// Its value is the number of spans to sample per second.
// Spans that matched the rules but exceeded the rate limit are not sampled.
type traceRulesSampler struct {
rules []SamplingRule // the rules to match spans with
globalRate float64 // a rate to apply when no rules match a span
limiter *rateLimiter // used to limit the volume of spans sampled
}
// newTraceRulesSampler configures a *traceRulesSampler instance using the given set of rules.
// Invalid rules or environment variable values are tolerated, by logging warnings and then ignoring them.
func newTraceRulesSampler(rules []SamplingRule) *traceRulesSampler {
return &traceRulesSampler{
rules: rules,
globalRate: globalSampleRate(),
limiter: newRateLimiter(),
}
}
// globalSampleRate returns the sampling rate found in the DD_TRACE_SAMPLE_RATE environment variable.
// If it is invalid or not within the 0-1 range, NaN is returned.
func globalSampleRate() float64 {
defaultRate := math.NaN()
v := os.Getenv("DD_TRACE_SAMPLE_RATE")
if v == "" {
return defaultRate
}
r, err := strconv.ParseFloat(v, 64)
if err != nil {
log.Warn("ignoring DD_TRACE_SAMPLE_RATE: error: %v", err)
return defaultRate
}
if r >= 0.0 && r <= 1.0 {
return r
}
log.Warn("ignoring DD_TRACE_SAMPLE_RATE: out of range %f", r)
return defaultRate
}
func (rs *traceRulesSampler) enabled() bool {
return len(rs.rules) > 0 || !math.IsNaN(rs.globalRate)
}
// apply uses the sampling rules to determine the sampling rate for the
// provided span. If the rules don't match, and a default rate hasn't been
// set using DD_TRACE_SAMPLE_RATE, then it returns false and the span is not
// modified.
func (rs *traceRulesSampler) apply(span *span) bool {
if !rs.enabled() {
// short path when disabled
return false
}
var matched bool
rate := rs.globalRate
for _, rule := range rs.rules {
if rule.match(span) {
matched = true
rate = rule.Rate
break
}
}
if !matched && math.IsNaN(rate) {
// no matching rule or global rate, so we want to fall back
// to priority sampling
return false
}
rs.applyRule(span, rate, time.Now())
return true
}
func (rs *traceRulesSampler) applyRule(span *span, rate float64, now time.Time) {
span.SetTag(keyRulesSamplerAppliedRate, rate)
if !sampledByRate(span.TraceID, rate) {
span.setSamplingPriority(ext.PriorityUserReject, samplernames.RuleRate)
return
}
sampled, rate := rs.limiter.allowOne(now)
if sampled {
span.setSamplingPriority(ext.PriorityUserKeep, samplernames.RuleRate)
} else {
span.setSamplingPriority(ext.PriorityUserReject, samplernames.RuleRate)
}
span.SetTag(keyRulesSamplerLimiterRate, rate)
}
// limit returns the rate limit set in the rules sampler, controlled by DD_TRACE_RATE_LIMIT, and
// true if rules sampling is enabled. If not present it returns math.NaN() and false.
func (rs *traceRulesSampler) limit() (float64, bool) {
if rs.enabled() {
return float64(rs.limiter.limiter.Limit()), true
}
return math.NaN(), false
}
// defaultRateLimit specifies the default trace rate limit used when DD_TRACE_RATE_LIMIT is not set.
const defaultRateLimit = 100.0
// newRateLimiter returns a rate limiter which restricts the number of traces sampled per second.
// The limit is DD_TRACE_RATE_LIMIT if set, `defaultRateLimit` otherwise.
func newRateLimiter() *rateLimiter {
limit := defaultRateLimit
v := os.Getenv("DD_TRACE_RATE_LIMIT")
if v != "" {
l, err := strconv.ParseFloat(v, 64)
if err != nil {
log.Warn("DD_TRACE_RATE_LIMIT invalid, using default value %f: %v", limit, err)
} else if l < 0.0 {
log.Warn("DD_TRACE_RATE_LIMIT negative, using default value %f", limit)
} else {
// override the default limit
limit = l
}
}
return &rateLimiter{
limiter: rate.NewLimiter(rate.Limit(limit), int(math.Ceil(limit))),
prevTime: time.Now(),
}
}
// singleSpanRulesSampler allows a user-defined list of rules to apply to spans
// to sample single spans.
// These rules match based on the span's Service and Name. If empty value is supplied
// to either Service or Name field, it will default to "*", allow all.
// When making a sampling decision, the rules are checked in order until
// a match is found.
// If a match is found, the rate from that rule is used.
// If no match is found, no changes or further sampling is applied to the spans.
// The rate is used to determine if the span should be sampled, but an upper
// limit can be defined using the max_per_second field when supplying the rule.
// If max_per_second is absent in the rule, the default is allow all.
// Its value is the max number of spans to sample per second.
// Spans that matched the rules but exceeded the rate limit are not sampled.
type singleSpanRulesSampler struct {
rules []SamplingRule // the rules to match spans with
}
// newSingleSpanRulesSampler configures a *singleSpanRulesSampler instance using the given set of rules.
// Invalid rules or environment variable values are tolerated, by logging warnings and then ignoring them.
func newSingleSpanRulesSampler(rules []SamplingRule) *singleSpanRulesSampler {
return &singleSpanRulesSampler{
rules: rules,
}
}
func (rs *singleSpanRulesSampler) enabled() bool {
return len(rs.rules) > 0
}
// apply uses the sampling rules to determine the sampling rate for the
// provided span. If the rules don't match, then it returns false and the span is not
// modified.
func (rs *singleSpanRulesSampler) apply(span *span) bool {
for _, rule := range rs.rules {
if rule.match(span) {
rate := rule.Rate
span.setMetric(keyRulesSamplerAppliedRate, rate)
if !sampledByRate(span.SpanID, rate) {
return false
}
var sampled bool
if rule.limiter != nil {
sampled, rate = rule.limiter.allowOne(nowTime())
if !sampled {
return false
}
}
span.setMetric(keySpanSamplingMechanism, float64(samplernames.SingleSpan))
span.setMetric(keySingleSpanSamplingRuleRate, rate)
if rule.MaxPerSecond != 0 {
span.setMetric(keySingleSpanSamplingMPS, rule.MaxPerSecond)
}
return true
}
}
return false
}
// rateLimiter is a wrapper on top of golang.org/x/time/rate which implements a rate limiter but also
// returns the effective rate of allowance.
type rateLimiter struct {
limiter *rate.Limiter
mu sync.Mutex // guards below fields
prevTime time.Time // time at which prevAllowed and prevSeen were set
allowed float64 // number of spans allowed in the current period
seen float64 // number of spans seen in the current period
prevAllowed float64 // number of spans allowed in the previous period
prevSeen float64 // number of spans seen in the previous period
}
// allowOne returns the rate limiter's decision to allow the span to be sampled, and the
// effective rate at the time it is called. The effective rate is computed by averaging the rate
// for the previous second with the current rate
func (r *rateLimiter) allowOne(now time.Time) (bool, float64) {
r.mu.Lock()
defer r.mu.Unlock()
if d := now.Sub(r.prevTime); d >= time.Second {
// enough time has passed to reset the counters
if d.Truncate(time.Second) == time.Second && r.seen > 0 {
// exactly one second, so update prev
r.prevAllowed = r.allowed
r.prevSeen = r.seen
} else {
// more than one second, so reset previous rate
r.prevAllowed = 0
r.prevSeen = 0
}
r.prevTime = now
r.allowed = 0
r.seen = 0
}
r.seen++
var sampled bool
if r.limiter.AllowN(now, 1) {
r.allowed++
sampled = true
}
er := (r.prevAllowed + r.allowed) / (r.prevSeen + r.seen)
return sampled, er
}
// newSingleSpanRateLimiter returns a rate limiter which restricts the number of single spans sampled per second.
// This defaults to infinite, allow all behaviour. The MaxPerSecond value of the rule may override the default.
func newSingleSpanRateLimiter(mps float64) *rateLimiter {
limit := math.MaxFloat64
if mps > 0 {
limit = mps
}
return &rateLimiter{
limiter: rate.NewLimiter(rate.Limit(limit), int(math.Ceil(limit))),
prevTime: time.Now(),
}
}
// globMatch compiles pattern string into glob format, i.e. regular expressions with only '?'
// and '*' treated as regex metacharacters.
func globMatch(pattern string) *regexp.Regexp {
if pattern == "" {
return regexp.MustCompile("^.*$")
}
// escaping regex characters
pattern = regexp.QuoteMeta(pattern)
// replacing '?' and '*' with regex characters
pattern = strings.Replace(pattern, "\\?", ".", -1)
pattern = strings.Replace(pattern, "\\*", ".*", -1)
// pattern must match an entire string
return regexp.MustCompile(fmt.Sprintf("^%s$", pattern))
}
// samplingRulesFromEnv parses sampling rules from the DD_TRACE_SAMPLING_RULES,
// DD_SPAN_SAMPLING_RULES and DD_SPAN_SAMPLING_RULES_FILE environment variables.
func samplingRulesFromEnv() (trace, span []SamplingRule, err error) {
var errs []string
defer func() {
if len(errs) != 0 {
err = fmt.Errorf("\n\t%s", strings.Join(errs, "\n\t"))
}
}()
rulesFromEnv := os.Getenv("DD_TRACE_SAMPLING_RULES")
if rulesFromEnv != "" {
trace, err = unmarshalSamplingRules([]byte(rulesFromEnv), SamplingRuleTrace)
if err != nil {
errs = append(errs, err.Error())
}
}
span, err = unmarshalSamplingRules([]byte(os.Getenv("DD_SPAN_SAMPLING_RULES")), SamplingRuleSpan)
if err != nil {
errs = append(errs, err.Error())
}
rulesFile := os.Getenv("DD_SPAN_SAMPLING_RULES_FILE")
if len(span) != 0 {
if rulesFile != "" {
log.Warn("DIAGNOSTICS Error(s): DD_SPAN_SAMPLING_RULES is available and will take precedence over DD_SPAN_SAMPLING_RULES_FILE")
}
return trace, span, err
}
if rulesFile != "" {
rulesFromEnvFile, err := os.ReadFile(rulesFile)
if err != nil {
errs = append(errs, fmt.Sprintf("Couldn't read file from DD_SPAN_SAMPLING_RULES_FILE: %v", err))
}
span, err = unmarshalSamplingRules(rulesFromEnvFile, SamplingRuleSpan)
if err != nil {
errs = append(errs, err.Error())
}
}
return trace, span, err
}
// unmarshalSamplingRules unmarshals JSON from b and returns the sampling rules found, attributing
// the type t to them. If any errors are occurred, they are returned.
func unmarshalSamplingRules(b []byte, spanType SamplingRuleType) ([]SamplingRule, error) {
if len(b) == 0 {
return nil, nil
}
var jsonRules []struct {
Service string `json:"service"`
Name string `json:"name"`
Rate json.Number `json:"sample_rate"`
MaxPerSecond float64 `json:"max_per_second"`
}
err := json.Unmarshal(b, &jsonRules)
if err != nil {
return nil, fmt.Errorf("error unmarshalling JSON: %v", err)
}
rules := make([]SamplingRule, 0, len(jsonRules))
var errs []string
for i, v := range jsonRules {
if v.Rate == "" {
if spanType == SamplingRuleSpan {
v.Rate = "1"
} else {
errs = append(errs, fmt.Sprintf("at index %d: rate not provided", i))
continue
}
}
rate, err := v.Rate.Float64()
if err != nil {
errs = append(errs, fmt.Sprintf("at index %d: %v", i, err))
continue
}
if rate < 0.0 || rate > 1.0 {
errs = append(errs, fmt.Sprintf("at index %d: ignoring rule %+v: rate is out of [0.0, 1.0] range", i, v))
continue
}
switch spanType {
case SamplingRuleSpan:
rules = append(rules, SamplingRule{
Service: globMatch(v.Service),
Name: globMatch(v.Name),
Rate: rate,
MaxPerSecond: v.MaxPerSecond,
limiter: newSingleSpanRateLimiter(v.MaxPerSecond),
ruleType: SamplingRuleSpan,
})
case SamplingRuleTrace:
if v.Rate == "" {
errs = append(errs, fmt.Sprintf("at index %d: rate not provided", i))
continue
}
rate, err := v.Rate.Float64()
if err != nil {
errs = append(errs, fmt.Sprintf("at index %d: %v", i, err))
continue
}
if rate < 0.0 || rate > 1.0 {
errs = append(errs, fmt.Sprintf("at index %d: ignoring rule %+v: rate is out of [0.0, 1.0] range", i, v))
continue
}
switch {
case v.Service != "" && v.Name != "":
rules = append(rules, NameServiceRule(v.Name, v.Service, rate))
case v.Service != "":
rules = append(rules, ServiceRule(v.Service, rate))
case v.Name != "":
rules = append(rules, NameRule(v.Name, rate))
}
}
}
if len(errs) != 0 {
return rules, fmt.Errorf("%s", strings.Join(errs, "\n\t"))
}
return rules, nil
}
// MarshalJSON implements the json.Marshaler interface.
func (sr *SamplingRule) MarshalJSON() ([]byte, error) {
s := struct {
Service string `json:"service"`
Name string `json:"name"`
Rate float64 `json:"sample_rate"`
Type string `json:"type"`
MaxPerSecond *float64 `json:"max_per_second,omitempty"`
}{}
if sr.exactService != "" {
s.Service = sr.exactService
} else if sr.Service != nil {
s.Service = fmt.Sprintf("%s", sr.Service)
}
if sr.exactName != "" {
s.Name = sr.exactName
} else if sr.Name != nil {
s.Name = fmt.Sprintf("%s", sr.Name)
}
s.Rate = sr.Rate
s.Type = fmt.Sprintf("%v(%d)", sr.ruleType.String(), sr.ruleType)
if sr.MaxPerSecond != 0 {
s.MaxPerSecond = &sr.MaxPerSecond
}
return json.Marshal(&s)
}