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gauge.go
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gauge.go
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// includes code from
// https://raw.githubusercontent.com/rcrowley/go-metrics/master/sample.go
// Copyright 2012 Richard Crowley. All rights reserved.
package metrics
import "sync/atomic"
// Gauges hold an int64 value that can be set arbitrarily.
type Gauge interface {
Metric
Update(int64)
Value() int64
}
func NewGauge(meta *MetricMeta) Gauge {
if UseNilMetrics {
return NilGauge{}
}
return &StandardGauge{
MetricMeta: meta,
value: 0,
}
}
func RegGauge(name string, tagStrings ...string) Gauge {
tr := NewGauge(NewMetricMeta(name, tagStrings))
MetricStats.Register(tr)
return tr
}
// GaugeSnapshot is a read-only copy of another Gauge.
type GaugeSnapshot struct {
*MetricMeta
value int64
}
// Snapshot returns the snapshot.
func (g GaugeSnapshot) Snapshot() Metric { 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 g.value }
// NilGauge is a no-op Gauge.
type NilGauge struct{ *MetricMeta }
// Snapshot is a no-op.
func (NilGauge) Snapshot() Metric { 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 {
*MetricMeta
value int64
}
// Snapshot returns a read-only copy of the gauge.
func (g *StandardGauge) Snapshot() Metric {
return GaugeSnapshot{MetricMeta: g.MetricMeta, value: 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)
}