| // Copyright 2014 The Prometheus Authors |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package prometheus |
| |
| import ( |
| "encoding/json" |
| "expvar" |
| ) |
| |
| type expvarCollector struct { |
| exports map[string]*Desc |
| } |
| |
| // NewExpvarCollector returns a newly allocated expvar Collector that still has |
| // to be registered with a Prometheus registry. |
| // |
| // An expvar Collector collects metrics from the expvar interface. It provides a |
| // quick way to expose numeric values that are already exported via expvar as |
| // Prometheus metrics. Note that the data models of expvar and Prometheus are |
| // fundamentally different, and that the expvar Collector is inherently slower |
| // than native Prometheus metrics. Thus, the expvar Collector is probably great |
| // for experiments and prototying, but you should seriously consider a more |
| // direct implementation of Prometheus metrics for monitoring production |
| // systems. |
| // |
| // The exports map has the following meaning: |
| // |
| // The keys in the map correspond to expvar keys, i.e. for every expvar key you |
| // want to export as Prometheus metric, you need an entry in the exports |
| // map. The descriptor mapped to each key describes how to export the expvar |
| // value. It defines the name and the help string of the Prometheus metric |
| // proxying the expvar value. The type will always be Untyped. |
| // |
| // For descriptors without variable labels, the expvar value must be a number or |
| // a bool. The number is then directly exported as the Prometheus sample |
| // value. (For a bool, 'false' translates to 0 and 'true' to 1). Expvar values |
| // that are not numbers or bools are silently ignored. |
| // |
| // If the descriptor has one variable label, the expvar value must be an expvar |
| // map. The keys in the expvar map become the various values of the one |
| // Prometheus label. The values in the expvar map must be numbers or bools again |
| // as above. |
| // |
| // For descriptors with more than one variable label, the expvar must be a |
| // nested expvar map, i.e. where the values of the topmost map are maps again |
| // etc. until a depth is reached that corresponds to the number of labels. The |
| // leaves of that structure must be numbers or bools as above to serve as the |
| // sample values. |
| // |
| // Anything that does not fit into the scheme above is silently ignored. |
| func NewExpvarCollector(exports map[string]*Desc) Collector { |
| return &expvarCollector{ |
| exports: exports, |
| } |
| } |
| |
| // Describe implements Collector. |
| func (e *expvarCollector) Describe(ch chan<- *Desc) { |
| for _, desc := range e.exports { |
| ch <- desc |
| } |
| } |
| |
| // Collect implements Collector. |
| func (e *expvarCollector) Collect(ch chan<- Metric) { |
| for name, desc := range e.exports { |
| var m Metric |
| expVar := expvar.Get(name) |
| if expVar == nil { |
| continue |
| } |
| var v interface{} |
| labels := make([]string, len(desc.variableLabels)) |
| if err := json.Unmarshal([]byte(expVar.String()), &v); err != nil { |
| ch <- NewInvalidMetric(desc, err) |
| continue |
| } |
| var processValue func(v interface{}, i int) |
| processValue = func(v interface{}, i int) { |
| if i >= len(labels) { |
| copiedLabels := append(make([]string, 0, len(labels)), labels...) |
| switch v := v.(type) { |
| case float64: |
| m = MustNewConstMetric(desc, UntypedValue, v, copiedLabels...) |
| case bool: |
| if v { |
| m = MustNewConstMetric(desc, UntypedValue, 1, copiedLabels...) |
| } else { |
| m = MustNewConstMetric(desc, UntypedValue, 0, copiedLabels...) |
| } |
| default: |
| return |
| } |
| ch <- m |
| return |
| } |
| vm, ok := v.(map[string]interface{}) |
| if !ok { |
| return |
| } |
| for lv, val := range vm { |
| labels[i] = lv |
| processValue(val, i+1) |
| } |
| } |
| processValue(v, 0) |
| } |
| } |