123 lines
3.1 KiB
Go
123 lines
3.1 KiB
Go
package metrics
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import (
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"fmt"
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"io"
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"math"
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"sync/atomic"
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)
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// NewGauge registers and returns gauge with the given name, which calls f to obtain gauge value.
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//
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// name must be valid Prometheus-compatible metric with possible labels.
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// For instance,
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//
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// - foo
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// - foo{bar="baz"}
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// - foo{bar="baz",aaa="b"}
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//
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// f must be safe for concurrent calls.
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// if f is nil, then it is expected that the gauge value is changed via Set(), Inc(), Dec() and Add() calls.
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//
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// The returned gauge is safe to use from concurrent goroutines.
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//
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// See also FloatCounter for working with floating-point values.
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func NewGauge(name string, f func() float64) *Gauge {
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return defaultSet.NewGauge(name, f)
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}
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// Gauge is a float64 gauge.
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type Gauge struct {
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// valueBits contains uint64 representation of float64 passed to Gauge.Set.
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valueBits uint64
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// f is a callback, which is called for returning the gauge value.
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f func() float64
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}
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// Get returns the current value for g.
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func (g *Gauge) Get() float64 {
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if f := g.f; f != nil {
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return f()
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}
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n := atomic.LoadUint64(&g.valueBits)
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return math.Float64frombits(n)
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}
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// Set sets g value to v.
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//
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// The g must be created with nil callback in order to be able to call this function.
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func (g *Gauge) Set(v float64) {
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if g.f != nil {
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panic(fmt.Errorf("cannot call Set on gauge created with non-nil callback"))
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}
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n := math.Float64bits(v)
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atomic.StoreUint64(&g.valueBits, n)
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}
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// Inc increments g by 1.
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//
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// The g must be created with nil callback in order to be able to call this function.
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func (g *Gauge) Inc() {
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g.Add(1)
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}
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// Dec decrements g by 1.
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//
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// The g must be created with nil callback in order to be able to call this function.
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func (g *Gauge) Dec() {
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g.Add(-1)
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}
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// Add adds fAdd to g. fAdd may be positive and negative.
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//
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// The g must be created with nil callback in order to be able to call this function.
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func (g *Gauge) Add(fAdd float64) {
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if g.f != nil {
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panic(fmt.Errorf("cannot call Set on gauge created with non-nil callback"))
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}
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for {
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n := atomic.LoadUint64(&g.valueBits)
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f := math.Float64frombits(n)
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fNew := f + fAdd
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nNew := math.Float64bits(fNew)
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if atomic.CompareAndSwapUint64(&g.valueBits, n, nNew) {
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break
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}
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}
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}
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func (g *Gauge) marshalTo(prefix string, w io.Writer) {
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v := g.Get()
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if float64(int64(v)) == v {
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// Marshal integer values without scientific notation
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fmt.Fprintf(w, "%s %d\n", prefix, int64(v))
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} else {
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fmt.Fprintf(w, "%s %g\n", prefix, v)
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}
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}
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func (g *Gauge) metricType() string {
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return "gauge"
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}
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// GetOrCreateGauge returns registered gauge with the given name
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// or creates new gauge if the registry doesn't contain gauge with
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// the given name.
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//
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// name must be valid Prometheus-compatible metric with possible labels.
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// For instance,
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//
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// - foo
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// - foo{bar="baz"}
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// - foo{bar="baz",aaa="b"}
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//
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// The returned gauge is safe to use from concurrent goroutines.
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//
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// Performance tip: prefer NewGauge instead of GetOrCreateGauge.
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//
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// See also FloatCounter for working with floating-point values.
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func GetOrCreateGauge(name string, f func() float64) *Gauge {
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return defaultSet.GetOrCreateGauge(name, f)
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}
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