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package metrics
import (
"sync"
"time"
)
// Meters count events to produce exponentially-weighted moving average rates
// at one-, five-, and fifteen-minutes and a mean rate.
type Meter interface {
Count() int64
Mark(int64)
Rate1() float64
Rate5() float64
Rate15() float64
RateMean() float64
Snapshot() Meter
Stop()
}
// GetOrRegisterMeter returns an existing Meter or constructs and registers a
// new StandardMeter.
// Be sure to unregister the meter from the registry once it is of no use to
// allow for garbage collection.
func GetOrRegisterMeter(name string, r Registry) Meter {
if nil == r {
r = DefaultRegistry
}
return r.GetOrRegister(name, NewMeter).(Meter)
}
// NewMeter constructs a new StandardMeter and launches a goroutine.
// Be sure to call Stop() once the meter is of no use to allow for garbage collection.
func NewMeter() Meter {
if !Enabled {
return NilMeter{}
}
m := newStandardMeter()
arbiter.Lock()
defer arbiter.Unlock()
arbiter.meters[m] = struct{}{}
if !arbiter.started {
arbiter.started = true
go arbiter.tick()
}
return m
}
// NewMeter constructs and registers a new StandardMeter and launches a
// goroutine.
// Be sure to unregister the meter from the registry once it is of no use to
// allow for garbage collection.
func NewRegisteredMeter(name string, r Registry) Meter {
c := NewMeter()
if nil == r {
r = DefaultRegistry
}
r.Register(name, c)
return c
}
// MeterSnapshot is a read-only copy of another Meter.
type MeterSnapshot struct {
count int64
rate1, rate5, rate15, rateMean float64
}
// Count returns the count of events at the time the snapshot was taken.
func (m *MeterSnapshot) Count() int64 { return m.count }
// Mark panics.
func (*MeterSnapshot) Mark(n int64) {
panic("Mark called on a MeterSnapshot")
}
// Rate1 returns the one-minute moving average rate of events per second at the
// time the snapshot was taken.
func (m *MeterSnapshot) Rate1() float64 { return m.rate1 }
// Rate5 returns the five-minute moving average rate of events per second at
// the time the snapshot was taken.
func (m *MeterSnapshot) Rate5() float64 { return m.rate5 }
// Rate15 returns the fifteen-minute moving average rate of events per second
// at the time the snapshot was taken.
func (m *MeterSnapshot) Rate15() float64 { return m.rate15 }
// RateMean returns the meter's mean rate of events per second at the time the
// snapshot was taken.
func (m *MeterSnapshot) RateMean() float64 { return m.rateMean }
// Snapshot returns the snapshot.
func (m *MeterSnapshot) Snapshot() Meter { return m }
// Stop is a no-op.
func (m *MeterSnapshot) Stop() {}
// NilMeter is a no-op Meter.
type NilMeter struct{}
// Count is a no-op.
func (NilMeter) Count() int64 { return 0 }
// Mark is a no-op.
func (NilMeter) Mark(n int64) {}
// Rate1 is a no-op.
func (NilMeter) Rate1() float64 { return 0.0 }
// Rate5 is a no-op.
func (NilMeter) Rate5() float64 { return 0.0 }
// Rate15is a no-op.
func (NilMeter) Rate15() float64 { return 0.0 }
// RateMean is a no-op.
func (NilMeter) RateMean() float64 { return 0.0 }
// Snapshot is a no-op.
func (NilMeter) Snapshot() Meter { return NilMeter{} }
// Stop is a no-op.
func (NilMeter) Stop() {}
// StandardMeter is the standard implementation of a Meter.
type StandardMeter struct {
lock sync.RWMutex
snapshot *MeterSnapshot
a1, a5, a15 EWMA
startTime time.Time
stopped bool
}
func newStandardMeter() *StandardMeter {
return &StandardMeter{
snapshot: &MeterSnapshot{},
a1: NewEWMA1(),
a5: NewEWMA5(),
a15: NewEWMA15(),
startTime: time.Now(),
}
}
// Stop stops the meter, Mark() will be a no-op if you use it after being stopped.
func (m *StandardMeter) Stop() {
m.lock.Lock()
stopped := m.stopped
m.stopped = true
m.lock.Unlock()
if !stopped {
arbiter.Lock()
delete(arbiter.meters, m)
arbiter.Unlock()
}
}
// Count returns the number of events recorded.
func (m *StandardMeter) Count() int64 {
m.lock.RLock()
count := m.snapshot.count
m.lock.RUnlock()
return count
}
// Mark records the occurrence of n events.
func (m *StandardMeter) Mark(n int64) {
m.lock.Lock()
defer m.lock.Unlock()
if m.stopped {
return
}
m.snapshot.count += n
m.a1.Update(n)
m.a5.Update(n)
m.a15.Update(n)
m.updateSnapshot()
}
// Rate1 returns the one-minute moving average rate of events per second.
func (m *StandardMeter) Rate1() float64 {
m.lock.RLock()
rate1 := m.snapshot.rate1
m.lock.RUnlock()
return rate1
}
// Rate5 returns the five-minute moving average rate of events per second.
func (m *StandardMeter) Rate5() float64 {
m.lock.RLock()
rate5 := m.snapshot.rate5
m.lock.RUnlock()
return rate5
}
// Rate15 returns the fifteen-minute moving average rate of events per second.
func (m *StandardMeter) Rate15() float64 {
m.lock.RLock()
rate15 := m.snapshot.rate15
m.lock.RUnlock()
return rate15
}
// RateMean returns the meter's mean rate of events per second.
func (m *StandardMeter) RateMean() float64 {
m.lock.RLock()
rateMean := m.snapshot.rateMean
m.lock.RUnlock()
return rateMean
}
// Snapshot returns a read-only copy of the meter.
func (m *StandardMeter) Snapshot() Meter {
m.lock.RLock()
snapshot := *m.snapshot
m.lock.RUnlock()
return &snapshot
}
func (m *StandardMeter) updateSnapshot() {
// should run with write lock held on m.lock
snapshot := m.snapshot
snapshot.rate1 = m.a1.Rate()
snapshot.rate5 = m.a5.Rate()
snapshot.rate15 = m.a15.Rate()
snapshot.rateMean = float64(snapshot.count) / time.Since(m.startTime).Seconds()
}
func (m *StandardMeter) tick() {
m.lock.Lock()
defer m.lock.Unlock()
m.a1.Tick()
m.a5.Tick()
m.a15.Tick()
m.updateSnapshot()
}
// meterArbiter ticks meters every 5s from a single goroutine.
// meters are references in a set for future stopping.
type meterArbiter struct {
sync.RWMutex
started bool
meters map[*StandardMeter]struct{}
ticker *time.Ticker
}
var arbiter = meterArbiter{ticker: time.NewTicker(5e9), meters: make(map[*StandardMeter]struct{})}
// Ticks meters on the scheduled interval
func (ma *meterArbiter) tick() {
for range ma.ticker.C {
ma.tickMeters()
}
}
func (ma *meterArbiter) tickMeters() {
ma.RLock()
defer ma.RUnlock()
for meter := range ma.meters {
meter.tick()
}
}
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