mirror of https://github.com/ethereum/go-ethereum
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
118 lines
2.8 KiB
118 lines
2.8 KiB
package metrics
|
|
|
|
import (
|
|
"math"
|
|
"sync"
|
|
"sync/atomic"
|
|
)
|
|
|
|
// EWMAs continuously calculate an exponentially-weighted moving average
|
|
// based on an outside source of clock ticks.
|
|
type EWMA interface {
|
|
Rate() float64
|
|
Snapshot() EWMA
|
|
Tick()
|
|
Update(int64)
|
|
}
|
|
|
|
// NewEWMA constructs a new EWMA with the given alpha.
|
|
func NewEWMA(alpha float64) EWMA {
|
|
if UseNilMetrics {
|
|
return NilEWMA{}
|
|
}
|
|
return &StandardEWMA{alpha: alpha}
|
|
}
|
|
|
|
// NewEWMA1 constructs a new EWMA for a one-minute moving average.
|
|
func NewEWMA1() EWMA {
|
|
return NewEWMA(1 - math.Exp(-5.0/60.0/1))
|
|
}
|
|
|
|
// NewEWMA5 constructs a new EWMA for a five-minute moving average.
|
|
func NewEWMA5() EWMA {
|
|
return NewEWMA(1 - math.Exp(-5.0/60.0/5))
|
|
}
|
|
|
|
// NewEWMA15 constructs a new EWMA for a fifteen-minute moving average.
|
|
func NewEWMA15() EWMA {
|
|
return NewEWMA(1 - math.Exp(-5.0/60.0/15))
|
|
}
|
|
|
|
// EWMASnapshot is a read-only copy of another EWMA.
|
|
type EWMASnapshot float64
|
|
|
|
// Rate returns the rate of events per second at the time the snapshot was
|
|
// taken.
|
|
func (a EWMASnapshot) Rate() float64 { return float64(a) }
|
|
|
|
// Snapshot returns the snapshot.
|
|
func (a EWMASnapshot) Snapshot() EWMA { return a }
|
|
|
|
// Tick panics.
|
|
func (EWMASnapshot) Tick() {
|
|
panic("Tick called on an EWMASnapshot")
|
|
}
|
|
|
|
// Update panics.
|
|
func (EWMASnapshot) Update(int64) {
|
|
panic("Update called on an EWMASnapshot")
|
|
}
|
|
|
|
// NilEWMA is a no-op EWMA.
|
|
type NilEWMA struct{}
|
|
|
|
// Rate is a no-op.
|
|
func (NilEWMA) Rate() float64 { return 0.0 }
|
|
|
|
// Snapshot is a no-op.
|
|
func (NilEWMA) Snapshot() EWMA { return NilEWMA{} }
|
|
|
|
// Tick is a no-op.
|
|
func (NilEWMA) Tick() {}
|
|
|
|
// Update is a no-op.
|
|
func (NilEWMA) Update(n int64) {}
|
|
|
|
// StandardEWMA is the standard implementation of an EWMA and tracks the number
|
|
// of uncounted events and processes them on each tick. It uses the
|
|
// sync/atomic package to manage uncounted events.
|
|
type StandardEWMA struct {
|
|
uncounted int64 // /!\ this should be the first member to ensure 64-bit alignment
|
|
alpha float64
|
|
rate float64
|
|
init bool
|
|
mutex sync.Mutex
|
|
}
|
|
|
|
// Rate returns the moving average rate of events per second.
|
|
func (a *StandardEWMA) Rate() float64 {
|
|
a.mutex.Lock()
|
|
defer a.mutex.Unlock()
|
|
return a.rate * float64(1e9)
|
|
}
|
|
|
|
// Snapshot returns a read-only copy of the EWMA.
|
|
func (a *StandardEWMA) Snapshot() EWMA {
|
|
return EWMASnapshot(a.Rate())
|
|
}
|
|
|
|
// Tick ticks the clock to update the moving average. It assumes it is called
|
|
// every five seconds.
|
|
func (a *StandardEWMA) Tick() {
|
|
count := atomic.LoadInt64(&a.uncounted)
|
|
atomic.AddInt64(&a.uncounted, -count)
|
|
instantRate := float64(count) / float64(5e9)
|
|
a.mutex.Lock()
|
|
defer a.mutex.Unlock()
|
|
if a.init {
|
|
a.rate += a.alpha * (instantRate - a.rate)
|
|
} else {
|
|
a.init = true
|
|
a.rate = instantRate
|
|
}
|
|
}
|
|
|
|
// Update adds n uncounted events.
|
|
func (a *StandardEWMA) Update(n int64) {
|
|
atomic.AddInt64(&a.uncounted, n)
|
|
}
|
|
|