73 lines
1.7 KiB
Go
73 lines
1.7 KiB
Go
package tracer
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import (
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"math"
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"sync"
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"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
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)
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// Sampler is the generic interface of any sampler. It must be safe for concurrent use.
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type Sampler interface {
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// Sample returns true if the given span should be sampled.
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Sample(span Span) bool
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}
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// RateSampler is a sampler implementation which randomly selects spans using a
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// provided rate. For example, a rate of 0.75 will permit 75% of the spans.
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// RateSampler implementations should be safe for concurrent use.
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type RateSampler interface {
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Sampler
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// Rate returns the current sample rate.
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Rate() float64
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// SetRate sets a new sample rate.
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SetRate(rate float64)
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}
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// rateSampler samples from a sample rate.
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type rateSampler struct {
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sync.RWMutex
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rate float64
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}
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// NewAllSampler is a short-hand for NewRateSampler(1). It is all-permissive.
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func NewAllSampler() RateSampler { return NewRateSampler(1) }
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// NewRateSampler returns an initialized RateSampler with a given sample rate.
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func NewRateSampler(rate float64) RateSampler {
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return &rateSampler{rate: rate}
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}
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// Rate returns the current rate of the sampler.
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func (r *rateSampler) Rate() float64 {
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r.RLock()
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defer r.RUnlock()
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return r.rate
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}
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// SetRate sets a new sampling rate.
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func (r *rateSampler) SetRate(rate float64) {
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r.Lock()
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r.rate = rate
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r.Unlock()
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}
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// constants used for the Knuth hashing, same as agent.
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const knuthFactor = uint64(1111111111111111111)
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// Sample returns true if the given span should be sampled.
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func (r *rateSampler) Sample(spn ddtrace.Span) bool {
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s, ok := spn.(*span)
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if !ok {
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return false
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}
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r.RLock()
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defer r.RUnlock()
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if r.rate < 1 {
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return s.TraceID*knuthFactor < uint64(r.rate*math.MaxUint64)
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}
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return true
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}
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