mirror of https://github.com/knative/docs.git
108 lines
2.6 KiB
Go
108 lines
2.6 KiB
Go
package zipkin
|
|
|
|
import (
|
|
"fmt"
|
|
"math"
|
|
"math/rand"
|
|
"sync"
|
|
"time"
|
|
)
|
|
|
|
// Sampler functions return if a Zipkin span should be sampled, based on its
|
|
// traceID.
|
|
type Sampler func(id uint64) bool
|
|
|
|
func neverSample(_ uint64) bool { return false }
|
|
|
|
func alwaysSample(_ uint64) bool { return true }
|
|
|
|
// NewModuloSampler provides a generic type Sampler.
|
|
func NewModuloSampler(mod uint64) Sampler {
|
|
if mod < 2 {
|
|
return alwaysSample
|
|
}
|
|
return func(id uint64) bool {
|
|
return (id % mod) == 0
|
|
}
|
|
}
|
|
|
|
// NewBoundarySampler is appropriate for high-traffic instrumentation who
|
|
// provision random trace ids, and make the sampling decision only once.
|
|
// It defends against nodes in the cluster selecting exactly the same ids.
|
|
func NewBoundarySampler(rate float64, salt int64) (Sampler, error) {
|
|
if rate == 0.0 {
|
|
return neverSample, nil
|
|
}
|
|
if rate == 1.0 {
|
|
return alwaysSample, nil
|
|
}
|
|
if rate < 0.0001 || rate > 1 {
|
|
return nil, fmt.Errorf("rate should be 0.0 or between 0.0001 and 1: was %f", rate)
|
|
}
|
|
|
|
var (
|
|
boundary = int64(rate * 10000)
|
|
usalt = uint64(salt)
|
|
)
|
|
return func(id uint64) bool {
|
|
return int64(math.Abs(float64(id^usalt)))%10000 < boundary
|
|
}, nil
|
|
}
|
|
|
|
// NewCountingSampler is appropriate for low-traffic instrumentation or
|
|
// those who do not provision random trace ids. It is not appropriate for
|
|
// collectors as the sampling decision isn't idempotent (consistent based
|
|
// on trace id).
|
|
func NewCountingSampler(rate float64) (Sampler, error) {
|
|
if rate == 0.0 {
|
|
return neverSample, nil
|
|
}
|
|
if rate == 1.0 {
|
|
return alwaysSample, nil
|
|
}
|
|
if rate < 0.01 || rate > 1 {
|
|
return nil, fmt.Errorf("rate should be 0.0 or between 0.01 and 1: was %f", rate)
|
|
}
|
|
var (
|
|
i = 0
|
|
outOf100 = int(rate*100 + math.Copysign(0.5, rate*100)) // for rounding float to int conversion instead of truncation
|
|
decisions = randomBitSet(100, outOf100, rand.New(rand.NewSource(time.Now().UnixNano())))
|
|
mtx = &sync.Mutex{}
|
|
)
|
|
|
|
return func(_ uint64) bool {
|
|
mtx.Lock()
|
|
result := decisions[i]
|
|
i++
|
|
if i == 100 {
|
|
i = 0
|
|
}
|
|
mtx.Unlock()
|
|
return result
|
|
}, nil
|
|
}
|
|
|
|
/**
|
|
* Reservoir sampling algorithm borrowed from Stack Overflow.
|
|
*
|
|
* http://stackoverflow.com/questions/12817946/generate-a-random-bitset-with-n-1s
|
|
*/
|
|
func randomBitSet(size int, cardinality int, rnd *rand.Rand) []bool {
|
|
result := make([]bool, size)
|
|
chosen := make([]int, cardinality)
|
|
var i int
|
|
for i = 0; i < cardinality; i++ {
|
|
chosen[i] = i
|
|
result[i] = true
|
|
}
|
|
for ; i < size; i++ {
|
|
j := rnd.Intn(i + 1)
|
|
if j < cardinality {
|
|
result[chosen[j]] = false
|
|
result[i] = true
|
|
chosen[j] = i
|
|
}
|
|
}
|
|
return result
|
|
}
|