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