plugeth/metrics/gauge.go
2024-02-05 22:16:32 +01:00

99 lines
2.3 KiB
Go

package metrics
import "sync/atomic"
// gaugeSnapshot contains a readonly int64.
type GaugeSnapshot interface {
Value() int64
}
// Gauges hold an int64 value that can be set arbitrarily.
type Gauge interface {
Snapshot() GaugeSnapshot
Update(int64)
UpdateIfGt(int64)
Dec(int64)
Inc(int64)
}
// GetOrRegisterGauge returns an existing Gauge or constructs and registers a
// new StandardGauge.
func GetOrRegisterGauge(name string, r Registry) Gauge {
if nil == r {
r = DefaultRegistry
}
return r.GetOrRegister(name, NewGauge).(Gauge)
}
// NewGauge constructs a new StandardGauge.
func NewGauge() Gauge {
if !Enabled {
return NilGauge{}
}
return &StandardGauge{}
}
// NewRegisteredGauge constructs and registers a new StandardGauge.
func NewRegisteredGauge(name string, r Registry) Gauge {
c := NewGauge()
if nil == r {
r = DefaultRegistry
}
r.Register(name, c)
return c
}
// gaugeSnapshot is a read-only copy of another Gauge.
type gaugeSnapshot int64
// Value returns the value at the time the snapshot was taken.
func (g gaugeSnapshot) Value() int64 { return int64(g) }
// NilGauge is a no-op Gauge.
type NilGauge struct{}
func (NilGauge) Snapshot() GaugeSnapshot { return (*emptySnapshot)(nil) }
func (NilGauge) Update(v int64) {}
func (NilGauge) UpdateIfGt(v int64) {}
func (NilGauge) Dec(i int64) {}
func (NilGauge) Inc(i int64) {}
// StandardGauge is the standard implementation of a Gauge and uses the
// sync/atomic package to manage a single int64 value.
type StandardGauge struct {
value atomic.Int64
}
// Snapshot returns a read-only copy of the gauge.
func (g *StandardGauge) Snapshot() GaugeSnapshot {
return gaugeSnapshot(g.value.Load())
}
// Update updates the gauge's value.
func (g *StandardGauge) Update(v int64) {
g.value.Store(v)
}
// Update updates the gauge's value if v is larger then the current value.
func (g *StandardGauge) UpdateIfGt(v int64) {
for {
exist := g.value.Load()
if exist >= v {
break
}
if g.value.CompareAndSwap(exist, v) {
break
}
}
}
// Dec decrements the gauge's current value by the given amount.
func (g *StandardGauge) Dec(i int64) {
g.value.Add(-i)
}
// Inc increments the gauge's current value by the given amount.
func (g *StandardGauge) Inc(i int64) {
g.value.Add(i)
}