forked from mirror/client_golang
81 lines
3.8 KiB
Go
81 lines
3.8 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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// Collector is the interface implemented by anything that can be used by
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// Prometheus to collect metrics. A Collector has to be registered for
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// collection. See Register, MustRegister, RegisterOrGet, and MustRegisterOrGet.
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//
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// The stock metrics provided by this package (like Gauge, Counter, Summary) are
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// also Collectors (which only ever collect one metric, namely itself). An
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// implementer of Collector may, however, collect multiple metrics in a
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// coordinated fashion and/or create metrics on the fly. Examples for collectors
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// already implemented in this library are the metric vectors (i.e. collection
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// of multiple instances of the same Metric but with different label values)
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// like GaugeVec or SummaryVec, and the ExpvarCollector.
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//
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// (Two Collectors are considered equal if their
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// Describe method yields the same set of descriptors.)
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type Collector interface {
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// Describe sends the super-set of all possible descriptors of metrics
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// collected by this Collector to the provided channel and returns once
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// the last descriptor has been sent. The sent descriptors fulfill the
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// consistency and uniqueness requirements described in the Desc
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// documentation. (It is valid if one and the same Collector sends
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// duplicate descriptors. Those duplicates are simply ignored. However,
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// two different Collectors must not send duplicate descriptors.) This
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// method idempotently sends the same descriptors throughout the
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// lifetime of the Collector. If a Collector encounters an error while
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// executing this method, it must send an invalid descriptor (created
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// with NewInvalidDesc) to signal the error to the registry.
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Describe(chan<- *Desc)
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// Collect is called by Prometheus when collecting metrics. The
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// implementation sends each collected metric via the provided channel
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// and returns once the last metric has been sent. The descriptor of
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// each sent metric is one of those returned by Describe. Returned
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// metrics that share the same descriptor must differ in their variable
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// label values. This method may be called concurrently and must
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// therefore be implemented in a concurrency safe way. Blocking occurs
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// at the expense of total performance of rendering all registered
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// metrics. Ideally, Collector implementations support concurrent
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// readers. If a Collector finds itself unable to collect a metric, it
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// can signal the error to the registry by sending a Metric that will
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// return the error when its Write method is called.
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Collect(chan<- Metric)
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}
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// SelfCollector implements Collector for a single Metric so that that the
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// Metric collects itself. Add it as an anonymous field to a struct that
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// implements Metric, and call Init with the Metric itself as an argument.
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type SelfCollector struct {
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self Metric
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}
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// Init provides the SelfCollector with a reference to the metric it is supposed
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// to collect. It is usually called within the factory function to create a
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// metric. See example.
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func (c *SelfCollector) Init(self Metric) {
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c.self = self
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}
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// Describe implements Collector.
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func (c *SelfCollector) Describe(ch chan<- *Desc) {
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ch <- c.self.Desc()
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}
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// Collect implements Collector.
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func (c *SelfCollector) Collect(ch chan<- Metric) {
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ch <- c.self
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}
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