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package metrics
import "sync/atomic"
// Gauges hold an int64 value that can be set arbitrarily.
type Gauge interface {
Snapshot() Gauge
Update(int64)
Value() 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{0}
}
// 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
}
// NewFunctionalGauge constructs a new FunctionalGauge.
func NewFunctionalGauge(f func() int64) Gauge {
if !Enabled {
return NilGauge{}
}
return &FunctionalGauge{value: f}
}
// NewRegisteredFunctionalGauge constructs and registers a new StandardGauge.
func NewRegisteredFunctionalGauge(name string, r Registry, f func() int64) Gauge {
c := NewFunctionalGauge(f)
if nil == r {
r = DefaultRegistry
}
r.Register(name, c)
return c
}
// GaugeSnapshot is a read-only copy of another Gauge.
type GaugeSnapshot int64
// Snapshot returns the snapshot.
func (g GaugeSnapshot) Snapshot() Gauge { return g }
// Update panics.
func (GaugeSnapshot) Update(int64) {
panic("Update called on a GaugeSnapshot")
}
// 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{}
// Snapshot is a no-op.
func (NilGauge) Snapshot() Gauge { return NilGauge{} }
// Update is a no-op.
func (NilGauge) Update(v int64) {}
// Value is a no-op.
func (NilGauge) Value() int64 { return 0 }
// StandardGauge is the standard implementation of a Gauge and uses the
// sync/atomic package to manage a single int64 value.
type StandardGauge struct {
value int64
}
// Snapshot returns a read-only copy of the gauge.
func (g *StandardGauge) Snapshot() Gauge {
return GaugeSnapshot(g.Value())
}
// Update updates the gauge's value.
func (g *StandardGauge) Update(v int64) {
atomic.StoreInt64(&g.value, v)
}
// Value returns the gauge's current value.
func (g *StandardGauge) Value() int64 {
return atomic.LoadInt64(&g.value)
}
// FunctionalGauge returns value from given function
type FunctionalGauge struct {
value func() int64
}
// Value returns the gauge's current value.
func (g FunctionalGauge) Value() int64 {
return g.value()
}
// Snapshot returns the snapshot.
func (g FunctionalGauge) Snapshot() Gauge { return GaugeSnapshot(g.Value()) }
// Update panics.
func (FunctionalGauge) Update(int64) {
panic("Update called on a FunctionalGauge")
}
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