khenaidoo | ab1f7bd | 2019-11-14 14:00:27 -0500 | [diff] [blame] | 1 | // Copyright 2014 The Prometheus Authors |
| 2 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 3 | // you may not use this file except in compliance with the License. |
| 4 | // You may obtain a copy of the License at |
| 5 | // |
| 6 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 7 | // |
| 8 | // Unless required by applicable law or agreed to in writing, software |
| 9 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 10 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 11 | // See the License for the specific language governing permissions and |
| 12 | // limitations under the License. |
| 13 | |
| 14 | package prometheus |
| 15 | |
| 16 | import ( |
| 17 | "fmt" |
| 18 | "sort" |
| 19 | |
| 20 | "github.com/golang/protobuf/proto" |
| 21 | |
| 22 | dto "github.com/prometheus/client_model/go" |
| 23 | ) |
| 24 | |
| 25 | // ValueType is an enumeration of metric types that represent a simple value. |
| 26 | type ValueType int |
| 27 | |
| 28 | // Possible values for the ValueType enum. |
| 29 | const ( |
| 30 | _ ValueType = iota |
| 31 | CounterValue |
| 32 | GaugeValue |
| 33 | UntypedValue |
| 34 | ) |
| 35 | |
| 36 | // valueFunc is a generic metric for simple values retrieved on collect time |
| 37 | // from a function. It implements Metric and Collector. Its effective type is |
| 38 | // determined by ValueType. This is a low-level building block used by the |
| 39 | // library to back the implementations of CounterFunc, GaugeFunc, and |
| 40 | // UntypedFunc. |
| 41 | type valueFunc struct { |
| 42 | selfCollector |
| 43 | |
| 44 | desc *Desc |
| 45 | valType ValueType |
| 46 | function func() float64 |
| 47 | labelPairs []*dto.LabelPair |
| 48 | } |
| 49 | |
| 50 | // newValueFunc returns a newly allocated valueFunc with the given Desc and |
| 51 | // ValueType. The value reported is determined by calling the given function |
| 52 | // from within the Write method. Take into account that metric collection may |
| 53 | // happen concurrently. If that results in concurrent calls to Write, like in |
| 54 | // the case where a valueFunc is directly registered with Prometheus, the |
| 55 | // provided function must be concurrency-safe. |
| 56 | func newValueFunc(desc *Desc, valueType ValueType, function func() float64) *valueFunc { |
| 57 | result := &valueFunc{ |
| 58 | desc: desc, |
| 59 | valType: valueType, |
| 60 | function: function, |
| 61 | labelPairs: makeLabelPairs(desc, nil), |
| 62 | } |
| 63 | result.init(result) |
| 64 | return result |
| 65 | } |
| 66 | |
| 67 | func (v *valueFunc) Desc() *Desc { |
| 68 | return v.desc |
| 69 | } |
| 70 | |
| 71 | func (v *valueFunc) Write(out *dto.Metric) error { |
| 72 | return populateMetric(v.valType, v.function(), v.labelPairs, out) |
| 73 | } |
| 74 | |
| 75 | // NewConstMetric returns a metric with one fixed value that cannot be |
| 76 | // changed. Users of this package will not have much use for it in regular |
| 77 | // operations. However, when implementing custom Collectors, it is useful as a |
| 78 | // throw-away metric that is generated on the fly to send it to Prometheus in |
| 79 | // the Collect method. NewConstMetric returns an error if the length of |
| 80 | // labelValues is not consistent with the variable labels in Desc or if Desc is |
| 81 | // invalid. |
| 82 | func NewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) (Metric, error) { |
| 83 | if desc.err != nil { |
| 84 | return nil, desc.err |
| 85 | } |
| 86 | if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil { |
| 87 | return nil, err |
| 88 | } |
| 89 | return &constMetric{ |
| 90 | desc: desc, |
| 91 | valType: valueType, |
| 92 | val: value, |
| 93 | labelPairs: makeLabelPairs(desc, labelValues), |
| 94 | }, nil |
| 95 | } |
| 96 | |
| 97 | // MustNewConstMetric is a version of NewConstMetric that panics where |
| 98 | // NewConstMetric would have returned an error. |
| 99 | func MustNewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) Metric { |
| 100 | m, err := NewConstMetric(desc, valueType, value, labelValues...) |
| 101 | if err != nil { |
| 102 | panic(err) |
| 103 | } |
| 104 | return m |
| 105 | } |
| 106 | |
| 107 | type constMetric struct { |
| 108 | desc *Desc |
| 109 | valType ValueType |
| 110 | val float64 |
| 111 | labelPairs []*dto.LabelPair |
| 112 | } |
| 113 | |
| 114 | func (m *constMetric) Desc() *Desc { |
| 115 | return m.desc |
| 116 | } |
| 117 | |
| 118 | func (m *constMetric) Write(out *dto.Metric) error { |
| 119 | return populateMetric(m.valType, m.val, m.labelPairs, out) |
| 120 | } |
| 121 | |
| 122 | func populateMetric( |
| 123 | t ValueType, |
| 124 | v float64, |
| 125 | labelPairs []*dto.LabelPair, |
| 126 | m *dto.Metric, |
| 127 | ) error { |
| 128 | m.Label = labelPairs |
| 129 | switch t { |
| 130 | case CounterValue: |
| 131 | m.Counter = &dto.Counter{Value: proto.Float64(v)} |
| 132 | case GaugeValue: |
| 133 | m.Gauge = &dto.Gauge{Value: proto.Float64(v)} |
| 134 | case UntypedValue: |
| 135 | m.Untyped = &dto.Untyped{Value: proto.Float64(v)} |
| 136 | default: |
| 137 | return fmt.Errorf("encountered unknown type %v", t) |
| 138 | } |
| 139 | return nil |
| 140 | } |
| 141 | |
| 142 | func makeLabelPairs(desc *Desc, labelValues []string) []*dto.LabelPair { |
| 143 | totalLen := len(desc.variableLabels) + len(desc.constLabelPairs) |
| 144 | if totalLen == 0 { |
| 145 | // Super fast path. |
| 146 | return nil |
| 147 | } |
| 148 | if len(desc.variableLabels) == 0 { |
| 149 | // Moderately fast path. |
| 150 | return desc.constLabelPairs |
| 151 | } |
| 152 | labelPairs := make([]*dto.LabelPair, 0, totalLen) |
| 153 | for i, n := range desc.variableLabels { |
| 154 | labelPairs = append(labelPairs, &dto.LabelPair{ |
| 155 | Name: proto.String(n), |
| 156 | Value: proto.String(labelValues[i]), |
| 157 | }) |
| 158 | } |
| 159 | labelPairs = append(labelPairs, desc.constLabelPairs...) |
| 160 | sort.Sort(labelPairSorter(labelPairs)) |
| 161 | return labelPairs |
| 162 | } |