Prince Pereira | c1c21d6 | 2021-04-22 08:38:15 +0000 | [diff] [blame] | 1 | package metrics |
| 2 | |
| 3 | import "sync/atomic" |
| 4 | |
| 5 | // Gauges hold an int64 value that can be set arbitrarily. |
| 6 | type Gauge interface { |
| 7 | Snapshot() Gauge |
| 8 | Update(int64) |
| 9 | Value() int64 |
| 10 | } |
| 11 | |
| 12 | // GetOrRegisterGauge returns an existing Gauge or constructs and registers a |
| 13 | // new StandardGauge. |
| 14 | func GetOrRegisterGauge(name string, r Registry) Gauge { |
| 15 | if nil == r { |
| 16 | r = DefaultRegistry |
| 17 | } |
| 18 | return r.GetOrRegister(name, NewGauge).(Gauge) |
| 19 | } |
| 20 | |
| 21 | // NewGauge constructs a new StandardGauge. |
| 22 | func NewGauge() Gauge { |
| 23 | if UseNilMetrics { |
| 24 | return NilGauge{} |
| 25 | } |
| 26 | return &StandardGauge{0} |
| 27 | } |
| 28 | |
| 29 | // NewRegisteredGauge constructs and registers a new StandardGauge. |
| 30 | func NewRegisteredGauge(name string, r Registry) Gauge { |
| 31 | c := NewGauge() |
| 32 | if nil == r { |
| 33 | r = DefaultRegistry |
| 34 | } |
| 35 | r.Register(name, c) |
| 36 | return c |
| 37 | } |
| 38 | |
| 39 | // NewFunctionalGauge constructs a new FunctionalGauge. |
| 40 | func NewFunctionalGauge(f func() int64) Gauge { |
| 41 | if UseNilMetrics { |
| 42 | return NilGauge{} |
| 43 | } |
| 44 | return &FunctionalGauge{value: f} |
| 45 | } |
| 46 | |
| 47 | // NewRegisteredFunctionalGauge constructs and registers a new StandardGauge. |
| 48 | func NewRegisteredFunctionalGauge(name string, r Registry, f func() int64) Gauge { |
| 49 | c := NewFunctionalGauge(f) |
| 50 | if nil == r { |
| 51 | r = DefaultRegistry |
| 52 | } |
| 53 | r.Register(name, c) |
| 54 | return c |
| 55 | } |
| 56 | |
| 57 | // GaugeSnapshot is a read-only copy of another Gauge. |
| 58 | type GaugeSnapshot int64 |
| 59 | |
| 60 | // Snapshot returns the snapshot. |
| 61 | func (g GaugeSnapshot) Snapshot() Gauge { return g } |
| 62 | |
| 63 | // Update panics. |
| 64 | func (GaugeSnapshot) Update(int64) { |
| 65 | panic("Update called on a GaugeSnapshot") |
| 66 | } |
| 67 | |
| 68 | // Value returns the value at the time the snapshot was taken. |
| 69 | func (g GaugeSnapshot) Value() int64 { return int64(g) } |
| 70 | |
| 71 | // NilGauge is a no-op Gauge. |
| 72 | type NilGauge struct{} |
| 73 | |
| 74 | // Snapshot is a no-op. |
| 75 | func (NilGauge) Snapshot() Gauge { return NilGauge{} } |
| 76 | |
| 77 | // Update is a no-op. |
| 78 | func (NilGauge) Update(v int64) {} |
| 79 | |
| 80 | // Value is a no-op. |
| 81 | func (NilGauge) Value() int64 { return 0 } |
| 82 | |
| 83 | // StandardGauge is the standard implementation of a Gauge and uses the |
| 84 | // sync/atomic package to manage a single int64 value. |
| 85 | type StandardGauge struct { |
| 86 | value int64 |
| 87 | } |
| 88 | |
| 89 | // Snapshot returns a read-only copy of the gauge. |
| 90 | func (g *StandardGauge) Snapshot() Gauge { |
| 91 | return GaugeSnapshot(g.Value()) |
| 92 | } |
| 93 | |
| 94 | // Update updates the gauge's value. |
| 95 | func (g *StandardGauge) Update(v int64) { |
| 96 | atomic.StoreInt64(&g.value, v) |
| 97 | } |
| 98 | |
| 99 | // Value returns the gauge's current value. |
| 100 | func (g *StandardGauge) Value() int64 { |
| 101 | return atomic.LoadInt64(&g.value) |
| 102 | } |
| 103 | |
| 104 | // FunctionalGauge returns value from given function |
| 105 | type FunctionalGauge struct { |
| 106 | value func() int64 |
| 107 | } |
| 108 | |
| 109 | // Value returns the gauge's current value. |
| 110 | func (g FunctionalGauge) Value() int64 { |
| 111 | return g.value() |
| 112 | } |
| 113 | |
| 114 | // Snapshot returns the snapshot. |
| 115 | func (g FunctionalGauge) Snapshot() Gauge { return GaugeSnapshot(g.Value()) } |
| 116 | |
| 117 | // Update panics. |
| 118 | func (FunctionalGauge) Update(int64) { |
| 119 | panic("Update called on a FunctionalGauge") |
| 120 | } |