khenaidoo | ffe076b | 2019-01-15 16:08:08 -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 | "encoding/json" |
| 18 | "expvar" |
| 19 | ) |
| 20 | |
| 21 | type expvarCollector struct { |
| 22 | exports map[string]*Desc |
| 23 | } |
| 24 | |
| 25 | // NewExpvarCollector returns a newly allocated expvar Collector that still has |
| 26 | // to be registered with a Prometheus registry. |
| 27 | // |
| 28 | // An expvar Collector collects metrics from the expvar interface. It provides a |
| 29 | // quick way to expose numeric values that are already exported via expvar as |
| 30 | // Prometheus metrics. Note that the data models of expvar and Prometheus are |
| 31 | // fundamentally different, and that the expvar Collector is inherently slower |
| 32 | // than native Prometheus metrics. Thus, the expvar Collector is probably great |
| 33 | // for experiments and prototying, but you should seriously consider a more |
| 34 | // direct implementation of Prometheus metrics for monitoring production |
| 35 | // systems. |
| 36 | // |
| 37 | // The exports map has the following meaning: |
| 38 | // |
| 39 | // The keys in the map correspond to expvar keys, i.e. for every expvar key you |
| 40 | // want to export as Prometheus metric, you need an entry in the exports |
| 41 | // map. The descriptor mapped to each key describes how to export the expvar |
| 42 | // value. It defines the name and the help string of the Prometheus metric |
| 43 | // proxying the expvar value. The type will always be Untyped. |
| 44 | // |
| 45 | // For descriptors without variable labels, the expvar value must be a number or |
| 46 | // a bool. The number is then directly exported as the Prometheus sample |
| 47 | // value. (For a bool, 'false' translates to 0 and 'true' to 1). Expvar values |
| 48 | // that are not numbers or bools are silently ignored. |
| 49 | // |
| 50 | // If the descriptor has one variable label, the expvar value must be an expvar |
| 51 | // map. The keys in the expvar map become the various values of the one |
| 52 | // Prometheus label. The values in the expvar map must be numbers or bools again |
| 53 | // as above. |
| 54 | // |
| 55 | // For descriptors with more than one variable label, the expvar must be a |
| 56 | // nested expvar map, i.e. where the values of the topmost map are maps again |
| 57 | // etc. until a depth is reached that corresponds to the number of labels. The |
| 58 | // leaves of that structure must be numbers or bools as above to serve as the |
| 59 | // sample values. |
| 60 | // |
| 61 | // Anything that does not fit into the scheme above is silently ignored. |
| 62 | func NewExpvarCollector(exports map[string]*Desc) Collector { |
| 63 | return &expvarCollector{ |
| 64 | exports: exports, |
| 65 | } |
| 66 | } |
| 67 | |
| 68 | // Describe implements Collector. |
| 69 | func (e *expvarCollector) Describe(ch chan<- *Desc) { |
| 70 | for _, desc := range e.exports { |
| 71 | ch <- desc |
| 72 | } |
| 73 | } |
| 74 | |
| 75 | // Collect implements Collector. |
| 76 | func (e *expvarCollector) Collect(ch chan<- Metric) { |
| 77 | for name, desc := range e.exports { |
| 78 | var m Metric |
| 79 | expVar := expvar.Get(name) |
| 80 | if expVar == nil { |
| 81 | continue |
| 82 | } |
| 83 | var v interface{} |
| 84 | labels := make([]string, len(desc.variableLabels)) |
| 85 | if err := json.Unmarshal([]byte(expVar.String()), &v); err != nil { |
| 86 | ch <- NewInvalidMetric(desc, err) |
| 87 | continue |
| 88 | } |
| 89 | var processValue func(v interface{}, i int) |
| 90 | processValue = func(v interface{}, i int) { |
| 91 | if i >= len(labels) { |
| 92 | copiedLabels := append(make([]string, 0, len(labels)), labels...) |
| 93 | switch v := v.(type) { |
| 94 | case float64: |
| 95 | m = MustNewConstMetric(desc, UntypedValue, v, copiedLabels...) |
| 96 | case bool: |
| 97 | if v { |
| 98 | m = MustNewConstMetric(desc, UntypedValue, 1, copiedLabels...) |
| 99 | } else { |
| 100 | m = MustNewConstMetric(desc, UntypedValue, 0, copiedLabels...) |
| 101 | } |
| 102 | default: |
| 103 | return |
| 104 | } |
| 105 | ch <- m |
| 106 | return |
| 107 | } |
| 108 | vm, ok := v.(map[string]interface{}) |
| 109 | if !ok { |
| 110 | return |
| 111 | } |
| 112 | for lv, val := range vm { |
| 113 | labels[i] = lv |
| 114 | processValue(val, i+1) |
| 115 | } |
| 116 | } |
| 117 | processValue(v, 0) |
| 118 | } |
| 119 | } |