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- // Copyright 2018 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 (
- "fmt"
- "sort"
- //nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
- "github.com/golang/protobuf/proto"
- dto "github.com/prometheus/client_model/go"
- )
- // WrapRegistererWith returns a Registerer wrapping the provided
- // Registerer. Collectors registered with the returned Registerer will be
- // registered with the wrapped Registerer in a modified way. The modified
- // Collector adds the provided Labels to all Metrics it collects (as
- // ConstLabels). The Metrics collected by the unmodified Collector must not
- // duplicate any of those labels. Wrapping a nil value is valid, resulting
- // in a no-op Registerer.
- //
- // WrapRegistererWith provides a way to add fixed labels to a subset of
- // Collectors. It should not be used to add fixed labels to all metrics
- // exposed. See also
- // https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels-not-static-scraped-labels
- //
- // Conflicts between Collectors registered through the original Registerer with
- // Collectors registered through the wrapping Registerer will still be
- // detected. Any AlreadyRegisteredError returned by the Register method of
- // either Registerer will contain the ExistingCollector in the form it was
- // provided to the respective registry.
- //
- // The Collector example demonstrates a use of WrapRegistererWith.
- func WrapRegistererWith(labels Labels, reg Registerer) Registerer {
- return &wrappingRegisterer{
- wrappedRegisterer: reg,
- labels: labels,
- }
- }
- // WrapRegistererWithPrefix returns a Registerer wrapping the provided
- // Registerer. Collectors registered with the returned Registerer will be
- // registered with the wrapped Registerer in a modified way. The modified
- // Collector adds the provided prefix to the name of all Metrics it collects.
- // Wrapping a nil value is valid, resulting in a no-op Registerer.
- //
- // WrapRegistererWithPrefix is useful to have one place to prefix all metrics of
- // a sub-system. To make this work, register metrics of the sub-system with the
- // wrapping Registerer returned by WrapRegistererWithPrefix. It is rarely useful
- // to use the same prefix for all metrics exposed. In particular, do not prefix
- // metric names that are standardized across applications, as that would break
- // horizontal monitoring, for example the metrics provided by the Go collector
- // (see NewGoCollector) and the process collector (see NewProcessCollector). (In
- // fact, those metrics are already prefixed with “go_” or “process_”,
- // respectively.)
- //
- // Conflicts between Collectors registered through the original Registerer with
- // Collectors registered through the wrapping Registerer will still be
- // detected. Any AlreadyRegisteredError returned by the Register method of
- // either Registerer will contain the ExistingCollector in the form it was
- // provided to the respective registry.
- func WrapRegistererWithPrefix(prefix string, reg Registerer) Registerer {
- return &wrappingRegisterer{
- wrappedRegisterer: reg,
- prefix: prefix,
- }
- }
- type wrappingRegisterer struct {
- wrappedRegisterer Registerer
- prefix string
- labels Labels
- }
- func (r *wrappingRegisterer) Register(c Collector) error {
- if r.wrappedRegisterer == nil {
- return nil
- }
- return r.wrappedRegisterer.Register(&wrappingCollector{
- wrappedCollector: c,
- prefix: r.prefix,
- labels: r.labels,
- })
- }
- func (r *wrappingRegisterer) MustRegister(cs ...Collector) {
- if r.wrappedRegisterer == nil {
- return
- }
- for _, c := range cs {
- if err := r.Register(c); err != nil {
- panic(err)
- }
- }
- }
- func (r *wrappingRegisterer) Unregister(c Collector) bool {
- if r.wrappedRegisterer == nil {
- return false
- }
- return r.wrappedRegisterer.Unregister(&wrappingCollector{
- wrappedCollector: c,
- prefix: r.prefix,
- labels: r.labels,
- })
- }
- type wrappingCollector struct {
- wrappedCollector Collector
- prefix string
- labels Labels
- }
- func (c *wrappingCollector) Collect(ch chan<- Metric) {
- wrappedCh := make(chan Metric)
- go func() {
- c.wrappedCollector.Collect(wrappedCh)
- close(wrappedCh)
- }()
- for m := range wrappedCh {
- ch <- &wrappingMetric{
- wrappedMetric: m,
- prefix: c.prefix,
- labels: c.labels,
- }
- }
- }
- func (c *wrappingCollector) Describe(ch chan<- *Desc) {
- wrappedCh := make(chan *Desc)
- go func() {
- c.wrappedCollector.Describe(wrappedCh)
- close(wrappedCh)
- }()
- for desc := range wrappedCh {
- ch <- wrapDesc(desc, c.prefix, c.labels)
- }
- }
- func (c *wrappingCollector) unwrapRecursively() Collector {
- switch wc := c.wrappedCollector.(type) {
- case *wrappingCollector:
- return wc.unwrapRecursively()
- default:
- return wc
- }
- }
- type wrappingMetric struct {
- wrappedMetric Metric
- prefix string
- labels Labels
- }
- func (m *wrappingMetric) Desc() *Desc {
- return wrapDesc(m.wrappedMetric.Desc(), m.prefix, m.labels)
- }
- func (m *wrappingMetric) Write(out *dto.Metric) error {
- if err := m.wrappedMetric.Write(out); err != nil {
- return err
- }
- if len(m.labels) == 0 {
- // No wrapping labels.
- return nil
- }
- for ln, lv := range m.labels {
- out.Label = append(out.Label, &dto.LabelPair{
- Name: proto.String(ln),
- Value: proto.String(lv),
- })
- }
- sort.Sort(labelPairSorter(out.Label))
- return nil
- }
- func wrapDesc(desc *Desc, prefix string, labels Labels) *Desc {
- constLabels := Labels{}
- for _, lp := range desc.constLabelPairs {
- constLabels[*lp.Name] = *lp.Value
- }
- for ln, lv := range labels {
- if _, alreadyUsed := constLabels[ln]; alreadyUsed {
- return &Desc{
- fqName: desc.fqName,
- help: desc.help,
- variableLabels: desc.variableLabels,
- constLabelPairs: desc.constLabelPairs,
- err: fmt.Errorf("attempted wrapping with already existing label name %q", ln),
- }
- }
- constLabels[ln] = lv
- }
- // NewDesc will do remaining validations.
- newDesc := NewDesc(prefix+desc.fqName, desc.help, desc.variableLabels, constLabels)
- // Propagate errors if there was any. This will override any errer
- // created by NewDesc above, i.e. earlier errors get precedence.
- if desc.err != nil {
- newDesc.err = desc.err
- }
- return newDesc
- }
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