khenaidoo | ab1f7bd | 2019-11-14 14:00:27 -0500 | [diff] [blame^] | 1 | // Copyright 2018 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 | // WrapRegistererWith returns a Registerer wrapping the provided |
| 26 | // Registerer. Collectors registered with the returned Registerer will be |
| 27 | // registered with the wrapped Registerer in a modified way. The modified |
| 28 | // Collector adds the provided Labels to all Metrics it collects (as |
| 29 | // ConstLabels). The Metrics collected by the unmodified Collector must not |
| 30 | // duplicate any of those labels. |
| 31 | // |
| 32 | // WrapRegistererWith provides a way to add fixed labels to a subset of |
| 33 | // Collectors. It should not be used to add fixed labels to all metrics exposed. |
| 34 | // |
| 35 | // Conflicts between Collectors registered through the original Registerer with |
| 36 | // Collectors registered through the wrapping Registerer will still be |
| 37 | // detected. Any AlreadyRegisteredError returned by the Register method of |
| 38 | // either Registerer will contain the ExistingCollector in the form it was |
| 39 | // provided to the respective registry. |
| 40 | // |
| 41 | // The Collector example demonstrates a use of WrapRegistererWith. |
| 42 | func WrapRegistererWith(labels Labels, reg Registerer) Registerer { |
| 43 | return &wrappingRegisterer{ |
| 44 | wrappedRegisterer: reg, |
| 45 | labels: labels, |
| 46 | } |
| 47 | } |
| 48 | |
| 49 | // WrapRegistererWithPrefix returns a Registerer wrapping the provided |
| 50 | // Registerer. Collectors registered with the returned Registerer will be |
| 51 | // registered with the wrapped Registerer in a modified way. The modified |
| 52 | // Collector adds the provided prefix to the name of all Metrics it collects. |
| 53 | // |
| 54 | // WrapRegistererWithPrefix is useful to have one place to prefix all metrics of |
| 55 | // a sub-system. To make this work, register metrics of the sub-system with the |
| 56 | // wrapping Registerer returned by WrapRegistererWithPrefix. It is rarely useful |
| 57 | // to use the same prefix for all metrics exposed. In particular, do not prefix |
| 58 | // metric names that are standardized across applications, as that would break |
| 59 | // horizontal monitoring, for example the metrics provided by the Go collector |
| 60 | // (see NewGoCollector) and the process collector (see NewProcessCollector). (In |
| 61 | // fact, those metrics are already prefixed with “go_” or “process_”, |
| 62 | // respectively.) |
| 63 | // |
| 64 | // Conflicts between Collectors registered through the original Registerer with |
| 65 | // Collectors registered through the wrapping Registerer will still be |
| 66 | // detected. Any AlreadyRegisteredError returned by the Register method of |
| 67 | // either Registerer will contain the ExistingCollector in the form it was |
| 68 | // provided to the respective registry. |
| 69 | func WrapRegistererWithPrefix(prefix string, reg Registerer) Registerer { |
| 70 | return &wrappingRegisterer{ |
| 71 | wrappedRegisterer: reg, |
| 72 | prefix: prefix, |
| 73 | } |
| 74 | } |
| 75 | |
| 76 | type wrappingRegisterer struct { |
| 77 | wrappedRegisterer Registerer |
| 78 | prefix string |
| 79 | labels Labels |
| 80 | } |
| 81 | |
| 82 | func (r *wrappingRegisterer) Register(c Collector) error { |
| 83 | return r.wrappedRegisterer.Register(&wrappingCollector{ |
| 84 | wrappedCollector: c, |
| 85 | prefix: r.prefix, |
| 86 | labels: r.labels, |
| 87 | }) |
| 88 | } |
| 89 | |
| 90 | func (r *wrappingRegisterer) MustRegister(cs ...Collector) { |
| 91 | for _, c := range cs { |
| 92 | if err := r.Register(c); err != nil { |
| 93 | panic(err) |
| 94 | } |
| 95 | } |
| 96 | } |
| 97 | |
| 98 | func (r *wrappingRegisterer) Unregister(c Collector) bool { |
| 99 | return r.wrappedRegisterer.Unregister(&wrappingCollector{ |
| 100 | wrappedCollector: c, |
| 101 | prefix: r.prefix, |
| 102 | labels: r.labels, |
| 103 | }) |
| 104 | } |
| 105 | |
| 106 | type wrappingCollector struct { |
| 107 | wrappedCollector Collector |
| 108 | prefix string |
| 109 | labels Labels |
| 110 | } |
| 111 | |
| 112 | func (c *wrappingCollector) Collect(ch chan<- Metric) { |
| 113 | wrappedCh := make(chan Metric) |
| 114 | go func() { |
| 115 | c.wrappedCollector.Collect(wrappedCh) |
| 116 | close(wrappedCh) |
| 117 | }() |
| 118 | for m := range wrappedCh { |
| 119 | ch <- &wrappingMetric{ |
| 120 | wrappedMetric: m, |
| 121 | prefix: c.prefix, |
| 122 | labels: c.labels, |
| 123 | } |
| 124 | } |
| 125 | } |
| 126 | |
| 127 | func (c *wrappingCollector) Describe(ch chan<- *Desc) { |
| 128 | wrappedCh := make(chan *Desc) |
| 129 | go func() { |
| 130 | c.wrappedCollector.Describe(wrappedCh) |
| 131 | close(wrappedCh) |
| 132 | }() |
| 133 | for desc := range wrappedCh { |
| 134 | ch <- wrapDesc(desc, c.prefix, c.labels) |
| 135 | } |
| 136 | } |
| 137 | |
| 138 | func (c *wrappingCollector) unwrapRecursively() Collector { |
| 139 | switch wc := c.wrappedCollector.(type) { |
| 140 | case *wrappingCollector: |
| 141 | return wc.unwrapRecursively() |
| 142 | default: |
| 143 | return wc |
| 144 | } |
| 145 | } |
| 146 | |
| 147 | type wrappingMetric struct { |
| 148 | wrappedMetric Metric |
| 149 | prefix string |
| 150 | labels Labels |
| 151 | } |
| 152 | |
| 153 | func (m *wrappingMetric) Desc() *Desc { |
| 154 | return wrapDesc(m.wrappedMetric.Desc(), m.prefix, m.labels) |
| 155 | } |
| 156 | |
| 157 | func (m *wrappingMetric) Write(out *dto.Metric) error { |
| 158 | if err := m.wrappedMetric.Write(out); err != nil { |
| 159 | return err |
| 160 | } |
| 161 | if len(m.labels) == 0 { |
| 162 | // No wrapping labels. |
| 163 | return nil |
| 164 | } |
| 165 | for ln, lv := range m.labels { |
| 166 | out.Label = append(out.Label, &dto.LabelPair{ |
| 167 | Name: proto.String(ln), |
| 168 | Value: proto.String(lv), |
| 169 | }) |
| 170 | } |
| 171 | sort.Sort(labelPairSorter(out.Label)) |
| 172 | return nil |
| 173 | } |
| 174 | |
| 175 | func wrapDesc(desc *Desc, prefix string, labels Labels) *Desc { |
| 176 | constLabels := Labels{} |
| 177 | for _, lp := range desc.constLabelPairs { |
| 178 | constLabels[*lp.Name] = *lp.Value |
| 179 | } |
| 180 | for ln, lv := range labels { |
| 181 | if _, alreadyUsed := constLabels[ln]; alreadyUsed { |
| 182 | return &Desc{ |
| 183 | fqName: desc.fqName, |
| 184 | help: desc.help, |
| 185 | variableLabels: desc.variableLabels, |
| 186 | constLabelPairs: desc.constLabelPairs, |
| 187 | err: fmt.Errorf("attempted wrapping with already existing label name %q", ln), |
| 188 | } |
| 189 | } |
| 190 | constLabels[ln] = lv |
| 191 | } |
| 192 | // NewDesc will do remaining validations. |
| 193 | newDesc := NewDesc(prefix+desc.fqName, desc.help, desc.variableLabels, constLabels) |
| 194 | // Propagate errors if there was any. This will override any errer |
| 195 | // created by NewDesc above, i.e. earlier errors get precedence. |
| 196 | if desc.err != nil { |
| 197 | newDesc.err = desc.err |
| 198 | } |
| 199 | return newDesc |
| 200 | } |