| // 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 is the core instrumentation package. It 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). There is |
| // also a sub-package promauto, which provides metrics constructors with |
| // automatic registration. |
| // |
| // 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. Furthermore, if you are not concerned with |
| // fine-grained control of when and how to register metrics with the registry, |
| // have a look at the promauto package, which will effectively allow you to |
| // ignore registration altogether in simple cases. |
| // |
| // 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. Alternatively, you |
| // could return no Desc at all, which will mark the Collector “unchecked”. No |
| // checks are performed at registration time, but metric consistency will still |
| // be ensured at scrape time, i.e. any inconsistencies will lead to scrape |
| // errors. Thus, with unchecked Collectors, the responsibility to not collect |
| // metrics that lead to inconsistencies in the total scrape result lies with the |
| // implementer of the Collector. While this is not a desirable state, it is |
| // sometimes necessary. The typical use case is a situation where the exact |
| // metrics to be returned by a Collector cannot be predicted at registration |
| // time, but the implementer has sufficient knowledge of the whole system to |
| // guarantee metric consistency. |
| // |
| // 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 DefaultRegisterer 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 DefaultRegisterer. 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 DefaultRegisterer 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. |
| // |
| // 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 |