| 1 | // SPDX-License-Identifier: GPL-3.0-or-later |
| 2 | |
| 3 | package metrix |
| 4 | |
| 5 | // snapshotGaugeInstrument writes sampled absolute gauge values. |
| 6 | type snapshotGaugeInstrument struct { |
| 7 | backend meterBackend |
| 8 | desc *instrumentDescriptor |
| 9 | scope HostScope |
| 10 | base []LabelSet |
| 11 | } |
| 12 | |
| 13 | // statefulGaugeInstrument writes maintained gauge values. |
| 14 | type statefulGaugeInstrument struct { |
| 15 | backend meterBackend |
| 16 | desc *instrumentDescriptor |
| 17 | scope HostScope |
| 18 | base []LabelSet |
| 19 | } |
| 20 | |
| 21 | // stagedGauge holds one in-cycle gauge sample for a single series identity. |
| 22 | type stagedGauge struct { |
| 23 | key string |
| 24 | name string |
| 25 | hostScopeKey string |
| 26 | hostScope HostScope |
| 27 | labels []Label |
| 28 | labelsKey string |
| 29 | desc *instrumentDescriptor |
| 30 | value SampleValue |
| 31 | } |
| 32 | |
| 33 | // Gauge declares or reuses a snapshot gauge under this meter. |
| 34 | func (m *snapshotMeter) Gauge(name string, opts ...InstrumentOption) SnapshotGauge { |
| 35 | desc, err := m.backend.registerInstrument(metricName(m.prefix, name), kindGauge, modeSnapshot, opts...) |
| 36 | if err != nil { |
| 37 | panic(err) |
| 38 | } |
| 39 | return &snapshotGaugeInstrument{ |
| 40 | backend: m.backend, |
| 41 | desc: desc, |
| 42 | scope: m.scope, |
| 43 | base: appendLabelSets(m.sets, nil), |
| 44 | } |
| 45 | } |
| 46 | |
| 47 | // Gauge declares or reuses a stateful gauge under this meter. |
| 48 | func (m *statefulMeter) Gauge(name string, opts ...InstrumentOption) StatefulGauge { |
| 49 | desc, err := m.backend.registerInstrument(metricName(m.prefix, name), kindGauge, modeStateful, opts...) |
| 50 | if err != nil { |
| 51 | panic(err) |
| 52 | } |
| 53 | return &statefulGaugeInstrument{ |
| 54 | backend: m.backend, |
| 55 | desc: desc, |
| 56 | scope: m.scope, |
| 57 | base: appendLabelSets(m.sets, nil), |
| 58 | } |
| 59 | } |
| 60 | |
| 61 | // Observe writes one absolute gauge value for this collect cycle. |
| 62 | func (g *snapshotGaugeInstrument) Observe(v SampleValue, labels ...LabelSet) { |
| 63 | g.backend.recordGaugeSet(g.desc, g.scope, v, appendLabelSets(g.base, labels)) |
| 64 | } |
| 65 | |
| 66 | // Set overwrites the staged gauge value for this collect cycle. |
| 67 | func (g *statefulGaugeInstrument) Set(v SampleValue, labels ...LabelSet) { |
| 68 | g.backend.recordGaugeSet(g.desc, g.scope, v, appendLabelSets(g.base, labels)) |
| 69 | } |
| 70 | |
| 71 | // Add accumulates on top of the committed baseline for this collect cycle. |
| 72 | func (g *statefulGaugeInstrument) Add(delta SampleValue, labels ...LabelSet) { |
| 73 | g.backend.recordGaugeAdd(g.desc, g.scope, delta, appendLabelSets(g.base, labels)) |
| 74 | } |
| 75 | |
| 76 | // recordGaugeSet writes one gauge sample into the active frame (last-write-wins in-cycle). |
| 77 | func (c *storeCore) recordGaugeSet(desc *instrumentDescriptor, scope HostScope, value SampleValue, sets []LabelSet) { |
| 78 | mustFiniteSample(value) |
| 79 | |
| 80 | c.mu.Lock() |
| 81 | defer c.mu.Unlock() |
| 82 | |
| 83 | if c.active == nil { |
| 84 | panic(errCycleInactive) |
| 85 | } |
| 86 | |
| 87 | labels, labelsKey, err := labelsFromSet(sets, c) |
| 88 | if err != nil { |
| 89 | panic(err) |
| 90 | } |
| 91 | scope, ok := c.prepareHostScopeForWriteLocked(scope) |
| 92 | if !ok { |
| 93 | return |
| 94 | } |
| 95 | |
| 96 | key := makeSeriesKey(scope.ScopeKey, desc.name, labelsKey) |
| 97 | entry, ok := c.active.gauges[key] |
| 98 | if !ok { |
| 99 | entry = &stagedGauge{ |
| 100 | key: key, |
| 101 | name: desc.name, |
| 102 | hostScopeKey: scope.ScopeKey, |
| 103 | hostScope: scope, |
| 104 | labels: labels, |
| 105 | labelsKey: labelsKey, |
| 106 | desc: desc, |
| 107 | } |
| 108 | c.active.gauges[key] = entry |
| 109 | } |
| 110 | entry.value = value |
| 111 | } |
| 112 | |
| 113 | // recordGaugeAdd accumulates delta into the active frame using committed baseline on first write. |
| 114 | func (c *storeCore) recordGaugeAdd(desc *instrumentDescriptor, scope HostScope, delta SampleValue, sets []LabelSet) { |
| 115 | mustFiniteSample(delta) |
| 116 | |
| 117 | c.mu.Lock() |
| 118 | defer c.mu.Unlock() |
| 119 | |
| 120 | if c.active == nil { |
| 121 | panic(errCycleInactive) |
| 122 | } |
| 123 | |
| 124 | labels, labelsKey, err := labelsFromSet(sets, c) |
| 125 | if err != nil { |
| 126 | panic(err) |
| 127 | } |
| 128 | scope, ok := c.prepareHostScopeForWriteLocked(scope) |
| 129 | if !ok { |
| 130 | return |
| 131 | } |
| 132 | |
| 133 | key := makeSeriesKey(scope.ScopeKey, desc.name, labelsKey) |
| 134 | entry, ok := c.active.gauges[key] |
| 135 | if !ok { |
| 136 | baseline := SampleValue(0) |
| 137 | if existing := c.snapshot.Load().series[key]; existing != nil { |
| 138 | baseline = existing.value |
| 139 | } |
| 140 | entry = &stagedGauge{ |
| 141 | key: key, |
| 142 | name: desc.name, |
| 143 | hostScopeKey: scope.ScopeKey, |
| 144 | hostScope: scope, |
| 145 | labels: labels, |
| 146 | labelsKey: labelsKey, |
| 147 | desc: desc, |
| 148 | value: baseline, |
| 149 | } |
| 150 | c.active.gauges[key] = entry |
| 151 | } |
| 152 | entry.value += delta |
| 153 | } |