187 lines
8.4 KiB
Go
187 lines
8.4 KiB
Go
// 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 provides metrics primitives to instrument code for
|
|
// monitoring. It also offers a registry for metrics. Sub-packages allow to
|
|
// expose the registered metrics via HTTP (package promhttp) or push them to a
|
|
// Pushgateway (package push).
|
|
//
|
|
// All exported functions and methods are safe to be used concurrently unless
|
|
// specified otherwise.
|
|
//
|
|
// A Basic Example
|
|
//
|
|
// As a starting point, a very basic usage example:
|
|
//
|
|
// package main
|
|
//
|
|
// import (
|
|
// "log"
|
|
// "net/http"
|
|
//
|
|
// "github.com/prometheus/client_golang/prometheus"
|
|
// "github.com/prometheus/client_golang/prometheus/promhttp"
|
|
// )
|
|
//
|
|
// var (
|
|
// cpuTemp = prometheus.NewGauge(prometheus.GaugeOpts{
|
|
// Name: "cpu_temperature_celsius",
|
|
// Help: "Current temperature of the CPU.",
|
|
// })
|
|
// hdFailures = prometheus.NewCounterVec(
|
|
// prometheus.CounterOpts{
|
|
// Name: "hd_errors_total",
|
|
// Help: "Number of hard-disk errors.",
|
|
// },
|
|
// []string{"device"},
|
|
// )
|
|
// )
|
|
//
|
|
// func init() {
|
|
// // Metrics have to be registered to be exposed:
|
|
// prometheus.MustRegister(cpuTemp)
|
|
// prometheus.MustRegister(hdFailures)
|
|
// }
|
|
//
|
|
// func main() {
|
|
// cpuTemp.Set(65.3)
|
|
// hdFailures.With(prometheus.Labels{"device":"/dev/sda"}).Inc()
|
|
//
|
|
// // The Handler function provides a default handler to expose metrics
|
|
// // via an HTTP server. "/metrics" is the usual endpoint for that.
|
|
// http.Handle("/metrics", promhttp.Handler())
|
|
// log.Fatal(http.ListenAndServe(":8080", nil))
|
|
// }
|
|
//
|
|
//
|
|
// This is a complete program that exports two metrics, a Gauge and a Counter,
|
|
// the latter with a label attached to turn it into a (one-dimensional) vector.
|
|
//
|
|
// Metrics
|
|
//
|
|
// The number of exported identifiers in this package might appear a bit
|
|
// overwhelming. However, in addition to the basic plumbing shown in the example
|
|
// above, you only need to understand the different metric types and their
|
|
// vector versions for basic usage.
|
|
//
|
|
// Above, you have already touched the Counter and the Gauge. There are two more
|
|
// advanced metric types: the Summary and Histogram. A more thorough description
|
|
// of those four metric types can be found in the Prometheus docs:
|
|
// https://prometheus.io/docs/concepts/metric_types/
|
|
//
|
|
// A fifth "type" of metric is Untyped. It behaves like a Gauge, but signals the
|
|
// Prometheus server not to assume anything about its type.
|
|
//
|
|
// In addition to the fundamental metric types Gauge, Counter, Summary,
|
|
// Histogram, and Untyped, a very important part of the Prometheus data model is
|
|
// the partitioning of samples along dimensions called labels, which results in
|
|
// metric vectors. The fundamental types are GaugeVec, CounterVec, SummaryVec,
|
|
// HistogramVec, and UntypedVec.
|
|
//
|
|
// While only the fundamental metric types implement the Metric interface, both
|
|
// the metrics and their vector versions implement the Collector interface. A
|
|
// Collector manages the collection of a number of Metrics, but for convenience,
|
|
// a Metric can also “collect itself”. Note that Gauge, Counter, Summary,
|
|
// Histogram, and Untyped are interfaces themselves while GaugeVec, CounterVec,
|
|
// SummaryVec, HistogramVec, and UntypedVec are not.
|
|
//
|
|
// To create instances of Metrics and their vector versions, you need a suitable
|
|
// …Opts struct, i.e. GaugeOpts, CounterOpts, SummaryOpts, HistogramOpts, or
|
|
// UntypedOpts.
|
|
//
|
|
// Custom Collectors and constant Metrics
|
|
//
|
|
// While you could create your own implementations of Metric, most likely you
|
|
// will only ever implement the Collector interface on your own. At a first
|
|
// glance, a custom Collector seems handy to bundle Metrics for common
|
|
// registration (with the prime example of the different metric vectors above,
|
|
// which bundle all the metrics of the same name but with different labels).
|
|
//
|
|
// There is a more involved use case, too: If you already have metrics
|
|
// available, created outside of the Prometheus context, you don't need the
|
|
// interface of the various Metric types. You essentially want to mirror the
|
|
// existing numbers into Prometheus Metrics during collection. An own
|
|
// implementation of the Collector interface is perfect for that. You can create
|
|
// Metric instances “on the fly” using NewConstMetric, NewConstHistogram, and
|
|
// NewConstSummary (and their respective Must… versions). That will happen in
|
|
// the Collect method. The Describe method has to return separate Desc
|
|
// instances, representative of the “throw-away” metrics to be created later.
|
|
// NewDesc comes in handy to create those Desc instances.
|
|
//
|
|
// The Collector example illustrates the use case. You can also look at the
|
|
// source code of the processCollector (mirroring process metrics), the
|
|
// goCollector (mirroring Go metrics), or the expvarCollector (mirroring expvar
|
|
// metrics) as examples that are used in this package itself.
|
|
//
|
|
// If you just need to call a function to get a single float value to collect as
|
|
// a metric, GaugeFunc, CounterFunc, or UntypedFunc might be interesting
|
|
// shortcuts.
|
|
//
|
|
// Advanced Uses of the Registry
|
|
//
|
|
// While MustRegister is the by far most common way of registering a Collector,
|
|
// sometimes you might want to handle the errors the registration might cause.
|
|
// As suggested by the name, MustRegister panics if an error occurs. With the
|
|
// Register function, the error is returned and can be handled.
|
|
//
|
|
// An error is returned if the registered Collector is incompatible or
|
|
// inconsistent with already registered metrics. The registry aims for
|
|
// consistency of the collected metrics according to the Prometheus data model.
|
|
// Inconsistencies are ideally detected at registration time, not at collect
|
|
// time. The former will usually be detected at start-up time of a program,
|
|
// while the latter will only happen at scrape time, possibly not even on the
|
|
// first scrape if the inconsistency only becomes relevant later. That is the
|
|
// main reason why a Collector and a Metric have to describe themselves to the
|
|
// registry.
|
|
//
|
|
// So far, everything we did operated on the so-called default registry, as it
|
|
// can be found in the global DefaultRegistry variable. With NewRegistry, you
|
|
// can create a custom registry, or you can even implement the Registerer or
|
|
// Gatherer interfaces yourself. The methods Register and Unregister work in the
|
|
// same way on a custom registry as the global functions Register and Unregister
|
|
// on the default registry.
|
|
//
|
|
// There are a number of uses for custom registries: You can use registries with
|
|
// special properties, see NewPedanticRegistry. You can avoid global state, as
|
|
// it is imposed by the DefaultRegistry. You can use multiple registries at the
|
|
// same time to expose different metrics in different ways. You can use separate
|
|
// registries for testing purposes.
|
|
//
|
|
// Also note that the DefaultRegistry comes registered with a Collector for Go
|
|
// runtime metrics (via NewGoCollector) and a Collector for process metrics (via
|
|
// NewProcessCollector). With a custom registry, you are in control and decide
|
|
// yourself about the Collectors to register.
|
|
//
|
|
// HTTP Exposition
|
|
//
|
|
// The Registry implements the Gatherer interface. The caller of the Gather
|
|
// method can then expose the gathered metrics in some way. Usually, the metrics
|
|
// are served via HTTP on the /metrics endpoint. That's happening in the example
|
|
// above. The tools to expose metrics via HTTP are in the promhttp sub-package.
|
|
// (The top-level functions in the prometheus package are deprecated.)
|
|
//
|
|
// Pushing to the Pushgateway
|
|
//
|
|
// Function for pushing to the Pushgateway can be found in the push sub-package.
|
|
//
|
|
// Graphite Bridge
|
|
//
|
|
// Functions and examples to push metrics from a Gatherer to Graphite can be
|
|
// found in the graphite sub-package.
|
|
//
|
|
// Other Means of Exposition
|
|
//
|
|
// More ways of exposing metrics can easily be added by following the approaches
|
|
// of the existing implementations.
|
|
package prometheus
|