package prometheus

Import Path
	github.com/prometheus/client_golang/prometheus (on go.dev)

Dependency Relation
	imports 25 packages, and imported by 2 packages

Involved Source Files

	      build_info.go
	      collector.go
	      counter.go
	      desc.go
	   d➜ doc.go
		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.

	      expvar_collector.go
	      fnv.go
	      gauge.go
	      go_collector.go
	      histogram.go
	      labels.go
	      metric.go
	      observer.go
	      process_collector.go
	      process_collector_other.go
	      registry.go
	      summary.go
	      timer.go
	      untyped.go
	      value.go
	      vec.go
	      wrap.go
Code Examples

	Collector
		package main
		
		import (
			"log"
			"net/http"
		
			"github.com/prometheus/client_golang/prometheus"
			"github.com/prometheus/client_golang/prometheus/promhttp"
		)
		
		// ClusterManager is an example for a system that might have been built without
		// Prometheus in mind. It models a central manager of jobs running in a
		// cluster. Thus, we implement a custom Collector called
		// ClusterManagerCollector, which collects information from a ClusterManager
		// using its provided methods and turns them into Prometheus Metrics for
		// collection.
		//
		// An additional challenge is that multiple instances of the ClusterManager are
		// run within the same binary, each in charge of a different zone. We need to
		// make use of wrapping Registerers to be able to register each
		// ClusterManagerCollector instance with Prometheus.
		type ClusterManager struct {
			Zone string
			// Contains many more fields not listed in this example.
		}
		
		// ReallyExpensiveAssessmentOfTheSystemState is a mock for the data gathering a
		// real cluster manager would have to do. Since it may actually be really
		// expensive, it must only be called once per collection. This implementation,
		// obviously, only returns some made-up data.
		func (c *ClusterManager) ReallyExpensiveAssessmentOfTheSystemState() (
			oomCountByHost map[string]int, ramUsageByHost map[string]float64,
		) {
			// Just example fake data.
			oomCountByHost = map[string]int{
				"foo.example.org": 42,
				"bar.example.org": 2001,
			}
			ramUsageByHost = map[string]float64{
				"foo.example.org": 6.023e23,
				"bar.example.org": 3.14,
			}
			return
		}
		
		// ClusterManagerCollector implements the Collector interface.
		type ClusterManagerCollector struct {
			ClusterManager *ClusterManager
		}
		
		// Descriptors used by the ClusterManagerCollector below.
		var (
			oomCountDesc = prometheus.NewDesc(
				"clustermanager_oom_crashes_total",
				"Number of OOM crashes.",
				[]string{"host"}, nil,
			)
			ramUsageDesc = prometheus.NewDesc(
				"clustermanager_ram_usage_bytes",
				"RAM usage as reported to the cluster manager.",
				[]string{"host"}, nil,
			)
		)
		
		// Describe is implemented with DescribeByCollect. That's possible because the
		// Collect method will always return the same two metrics with the same two
		// descriptors.
		func (cc ClusterManagerCollector) Describe(ch chan<- *prometheus.Desc) {
			prometheus.DescribeByCollect(cc, ch)
		}
		
		// Collect first triggers the ReallyExpensiveAssessmentOfTheSystemState. Then it
		// creates constant metrics for each host on the fly based on the returned data.
		//
		// Note that Collect could be called concurrently, so we depend on
		// ReallyExpensiveAssessmentOfTheSystemState to be concurrency-safe.
		func (cc ClusterManagerCollector) Collect(ch chan<- prometheus.Metric) {
			oomCountByHost, ramUsageByHost := cc.ClusterManager.ReallyExpensiveAssessmentOfTheSystemState()
			for host, oomCount := range oomCountByHost {
				ch <- prometheus.MustNewConstMetric(
					oomCountDesc,
					prometheus.CounterValue,
					float64(oomCount),
					host,
				)
			}
			for host, ramUsage := range ramUsageByHost {
				ch <- prometheus.MustNewConstMetric(
					ramUsageDesc,
					prometheus.GaugeValue,
					ramUsage,
					host,
				)
			}
		}
		
		// NewClusterManager first creates a Prometheus-ignorant ClusterManager
		// instance. Then, it creates a ClusterManagerCollector for the just created
		// ClusterManager. Finally, it registers the ClusterManagerCollector with a
		// wrapping Registerer that adds the zone as a label. In this way, the metrics
		// collected by different ClusterManagerCollectors do not collide.
		func NewClusterManager(zone string, reg prometheus.Registerer) *ClusterManager {
			c := &ClusterManager{
				Zone: zone,
			}
			cc := ClusterManagerCollector{ClusterManager: c}
			prometheus.WrapRegistererWith(prometheus.Labels{"zone": zone}, reg).MustRegister(cc)
			return c
		}
		
		func main() {
			// Since we are dealing with custom Collector implementations, it might
			// be a good idea to try it out with a pedantic registry.
			reg := prometheus.NewPedanticRegistry()
		
			// Construct cluster managers. In real code, we would assign them to
			// variables to then do something with them.
			NewClusterManager("db", reg)
			NewClusterManager("ca", reg)
		
			// Add the standard process and Go metrics to the custom registry.
			reg.MustRegister(
				prometheus.NewProcessCollector(prometheus.ProcessCollectorOpts{}),
				prometheus.NewGoCollector(),
			)
		
			http.Handle("/metrics", promhttp.HandlerFor(reg, promhttp.HandlerOpts{}))
			log.Fatal(http.ListenAndServe(":8080", nil))
		}


	Timer
		package main
		
		import (
			"math/rand"
			"time"
		
			"github.com/prometheus/client_golang/prometheus"
		)
		
		var (
			requestDuration = prometheus.NewHistogram(prometheus.HistogramOpts{
				Name:    "example_request_duration_seconds",
				Help:    "Histogram for the runtime of a simple example function.",
				Buckets: prometheus.LinearBuckets(0.01, 0.01, 10),
			})
		)
		
		func main() {
			// timer times this example function. It uses a Histogram, but a Summary
			// would also work, as both implement Observer. Check out
			// https://prometheus.io/docs/practices/histograms/ for differences.
			timer := prometheus.NewTimer(requestDuration)
			defer timer.ObserveDuration()
		
			// Do something here that takes time.
			time.Sleep(time.Duration(rand.NormFloat64()*10000+50000) * time.Microsecond)
		}


	Timer_complex
		package main
		
		import (
			"net/http"
		
			"github.com/prometheus/client_golang/prometheus"
		)
		
		var (
			// apiRequestDuration tracks the duration separate for each HTTP status
			// class (1xx, 2xx, ...). This creates a fair amount of time series on
			// the Prometheus server. Usually, you would track the duration of
			// serving HTTP request without partitioning by outcome. Do something
			// like this only if needed. Also note how only status classes are
			// tracked, not every single status code. The latter would create an
			// even larger amount of time series. Request counters partitioned by
			// status code are usually OK as each counter only creates one time
			// series. Histograms are way more expensive, so partition with care and
			// only where you really need separate latency tracking. Partitioning by
			// status class is only an example. In concrete cases, other partitions
			// might make more sense.
			apiRequestDuration = prometheus.NewHistogramVec(
				prometheus.HistogramOpts{
					Name:    "api_request_duration_seconds",
					Help:    "Histogram for the request duration of the public API, partitioned by status class.",
					Buckets: prometheus.ExponentialBuckets(0.1, 1.5, 5),
				},
				[]string{"status_class"},
			)
		)
		
		func handler(w http.ResponseWriter, r *http.Request) {
			status := http.StatusOK
			// The ObserverFunc gets called by the deferred ObserveDuration and
			// decides which Histogram's Observe method is called.
			timer := prometheus.NewTimer(prometheus.ObserverFunc(func(v float64) {
				switch {
				case status >= 500: // Server error.
					apiRequestDuration.WithLabelValues("5xx").Observe(v)
				case status >= 400: // Client error.
					apiRequestDuration.WithLabelValues("4xx").Observe(v)
				case status >= 300: // Redirection.
					apiRequestDuration.WithLabelValues("3xx").Observe(v)
				case status >= 200: // Success.
					apiRequestDuration.WithLabelValues("2xx").Observe(v)
				default: // Informational.
					apiRequestDuration.WithLabelValues("1xx").Observe(v)
				}
			}))
			defer timer.ObserveDuration()
		
			// Handle the request. Set status accordingly.
			// ...
		}
		
		func main() {
			http.HandleFunc("/api", handler)
		}


	Timer_gauge
		package main
		
		import (
			"os"
		
			"github.com/prometheus/client_golang/prometheus"
		)
		
		var (
			// If a function is called rarely (i.e. not more often than scrapes
			// happen) or ideally only once (like in a batch job), it can make sense
			// to use a Gauge for timing the function call. For timing a batch job
			// and pushing the result to a Pushgateway, see also the comprehensive
			// example in the push package.
			funcDuration = prometheus.NewGauge(prometheus.GaugeOpts{
				Name: "example_function_duration_seconds",
				Help: "Duration of the last call of an example function.",
			})
		)
		
		func run() error {
			// The Set method of the Gauge is used to observe the duration.
			timer := prometheus.NewTimer(prometheus.ObserverFunc(funcDuration.Set))
			defer timer.ObserveDuration()
		
			// Do something. Return errors as encountered. The use of 'defer' above
			// makes sure the function is still timed properly.
			return nil
		}
		
		func main() {
			if err := run(); err != nil {
				os.Exit(1)
			}
		}


Package-Level Type Names (total 62, in which 34 are exported)

	/* sort exporteds by: alphabet | popularity */
	 type AlreadyRegisteredError (struct)
		AlreadyRegisteredError is returned by the Register method if the Collector to
		be registered has already been registered before, or a different Collector
		that collects the same metrics has been registered before. Registration fails
		in that case, but you can detect from the kind of error what has
		happened. The error contains fields for the existing Collector and the
		(rejected) new Collector that equals the existing one. This can be used to
		find out if an equal Collector has been registered before and switch over to
		using the old one, as demonstrated in the example.

		Fields (total 2, both are exported)
			ExistingCollector Collector
			NewCollector Collector
		Methods (only one, which is exported)
			( T) Error() string
		Implements (at least one exported)
			 T : error

	 type Collector (interface)
		Collector is the interface implemented by anything that can be used by
		Prometheus to collect metrics. A Collector has to be registered for
		collection. See Registerer.Register.

		The stock metrics provided by this package (Gauge, Counter, Summary,
		Histogram, Untyped) are also Collectors (which only ever collect one metric,
		namely itself). An implementer of Collector may, however, collect multiple
		metrics in a coordinated fashion and/or create metrics on the fly. Examples
		for collectors already implemented in this library are the metric vectors
		(i.e. collection of multiple instances of the same Metric but with different
		label values) like GaugeVec or SummaryVec, and the ExpvarCollector.

		Methods (total 2, both are exported)
			( T) Collect(chan<- Metric)
				Collect is called by the Prometheus registry when collecting
				metrics. The implementation sends each collected metric via the
				provided channel and returns once the last metric has been sent. The
				descriptor of each sent metric is one of those returned by Describe
				(unless the Collector is unchecked, see above). Returned metrics that
				share the same descriptor must differ in their variable label
				values.

				This method may be called concurrently and must therefore be
				implemented in a concurrency safe way. Blocking occurs at the expense
				of total performance of rendering all registered metrics. Ideally,
				Collector implementations support concurrent readers.

			( T) Describe(chan<- *Desc)
				Describe sends the super-set of all possible descriptors of metrics
				collected by this Collector to the provided channel and returns once
				the last descriptor has been sent. The sent descriptors fulfill the
				consistency and uniqueness requirements described in the Desc
				documentation.

				It is valid if one and the same Collector sends duplicate
				descriptors. Those duplicates are simply ignored. However, two
				different Collectors must not send duplicate descriptors.

				Sending no descriptor at all marks the Collector as “unchecked”,
				i.e. no checks will be performed at registration time, and the
				Collector may yield any Metric it sees fit in its Collect method.

				This method idempotently sends the same descriptors throughout the
				lifetime of the Collector. It may be called concurrently and
				therefore must be implemented in a concurrency safe way.

				If a Collector encounters an error while executing this method, it
				must send an invalid descriptor (created with NewInvalidDesc) to
				signal the error to the registry.

		Implemented By (at least 26, in which 12 are exported)
			 Counter (interface)
			 CounterFunc (interface)
			 CounterVec
			 Gauge (interface)
			 GaugeFunc (interface)
			 GaugeVec
			 Histogram (interface)
			 HistogramVec
			 ObserverVec (interface)
			 Summary (interface)
			 SummaryVec
			 UntypedFunc (interface)
			/* 14+ unexporteds ... *//* 14+ unexporteds: */
			*counter
			*expvarCollector
			*gauge
			*goCollector
			*histogram
			*metricMap
			 metricVec
			*noObjectivesSummary
			*processCollector
			*selfCollector
			*summary
			*valueFunc
			*wrappingCollector
			*contrib.go.opencensus.io/exporter/prometheus.collector
		As Outputs Of (at least 4, all are exported)
			func NewBuildInfoCollector() Collector
			func NewExpvarCollector(exports map[string]*Desc) Collector
			func NewGoCollector() Collector
			func NewProcessCollector(opts ProcessCollectorOpts) Collector
		As Inputs Of (at least 12, in which 10 are exported)
			func DescribeByCollect(c Collector, descs chan<- *Desc)
			func MustRegister(cs ...Collector)
			func Register(c Collector) error
			func Unregister(c Collector) bool
			func Registerer.MustRegister(...Collector)
			func Registerer.Register(Collector) error
			func Registerer.Unregister(Collector) bool
			func (*Registry).MustRegister(cs ...Collector)
			func (*Registry).Register(c Collector) error
			func (*Registry).Unregister(c Collector) bool
			/* 2+ unexporteds ... *//* 2+ unexporteds: */
			func github.com/prometheus/client_golang/prometheus/promhttp.checkLabels(c Collector) (code bool, method bool)
			func github.com/prometheus/client_golang/prometheus/promhttp.isLabelCurried(c Collector, label string) bool

	 type Counter (interface)
		Counter is a Metric that represents a single numerical value that only ever
		goes up. That implies that it cannot be used to count items whose number can
		also go down, e.g. the number of currently running goroutines. Those
		"counters" are represented by Gauges.

		A Counter is typically used to count requests served, tasks completed, errors
		occurred, etc.

		To create Counter instances, use NewCounter.

		Methods (total 6, all are exported)
			( T) Add(float64)
				Add adds the given value to the counter. It panics if the value is <
				0.

			( T) Collect(chan<- Metric)
				Collect is called by the Prometheus registry when collecting
				metrics. The implementation sends each collected metric via the
				provided channel and returns once the last metric has been sent. The
				descriptor of each sent metric is one of those returned by Describe
				(unless the Collector is unchecked, see above). Returned metrics that
				share the same descriptor must differ in their variable label
				values.

				This method may be called concurrently and must therefore be
				implemented in a concurrency safe way. Blocking occurs at the expense
				of total performance of rendering all registered metrics. Ideally,
				Collector implementations support concurrent readers.

			( T) Desc() *Desc
				Desc returns the descriptor for the Metric. This method idempotently
				returns the same descriptor throughout the lifetime of the
				Metric. The returned descriptor is immutable by contract. A Metric
				unable to describe itself must return an invalid descriptor (created
				with NewInvalidDesc).

			( T) Describe(chan<- *Desc)
				Describe sends the super-set of all possible descriptors of metrics
				collected by this Collector to the provided channel and returns once
				the last descriptor has been sent. The sent descriptors fulfill the
				consistency and uniqueness requirements described in the Desc
				documentation.

				It is valid if one and the same Collector sends duplicate
				descriptors. Those duplicates are simply ignored. However, two
				different Collectors must not send duplicate descriptors.

				Sending no descriptor at all marks the Collector as “unchecked”,
				i.e. no checks will be performed at registration time, and the
				Collector may yield any Metric it sees fit in its Collect method.

				This method idempotently sends the same descriptors throughout the
				lifetime of the Collector. It may be called concurrently and
				therefore must be implemented in a concurrency safe way.

				If a Collector encounters an error while executing this method, it
				must send an invalid descriptor (created with NewInvalidDesc) to
				signal the error to the registry.

			( T) Inc()
				Inc increments the counter by 1. Use Add to increment it by arbitrary
				non-negative values.

			( T) Write(*dto.Metric) error
				Write encodes the Metric into a "Metric" Protocol Buffer data
				transmission object.

				Metric implementations must observe concurrency safety as reads of
				this metric may occur at any time, and any blocking occurs at the
				expense of total performance of rendering all registered
				metrics. Ideally, Metric implementations should support concurrent
				readers.

				While populating dto.Metric, it is the responsibility of the
				implementation to ensure validity of the Metric protobuf (like valid
				UTF-8 strings or syntactically valid metric and label names). It is
				recommended to sort labels lexicographically. Callers of Write should
				still make sure of sorting if they depend on it.

		Implemented By (at least 3, in which 1 are exported)
			 Gauge (interface)
			/* 2+ unexporteds ... *//* 2+ unexporteds: */
			*counter
			*gauge
		Implements (at least 5, all are exported)
			 T : Collector
			 T : CounterFunc
			 T : GaugeFunc
			 T : Metric
			 T : UntypedFunc
		As Outputs Of (at least 5, all are exported)
			func NewCounter(opts CounterOpts) Counter
			func (*CounterVec).GetMetricWith(labels Labels) (Counter, error)
			func (*CounterVec).GetMetricWithLabelValues(lvs ...string) (Counter, error)
			func (*CounterVec).With(labels Labels) Counter
			func (*CounterVec).WithLabelValues(lvs ...string) Counter

	 type CounterFunc (interface)
		CounterFunc is a Counter whose value is determined at collect time by calling a
		provided function.

		To create CounterFunc instances, use NewCounterFunc.

		Methods (total 4, all are exported)
			( T) Collect(chan<- Metric)
				Collect is called by the Prometheus registry when collecting
				metrics. The implementation sends each collected metric via the
				provided channel and returns once the last metric has been sent. The
				descriptor of each sent metric is one of those returned by Describe
				(unless the Collector is unchecked, see above). Returned metrics that
				share the same descriptor must differ in their variable label
				values.

				This method may be called concurrently and must therefore be
				implemented in a concurrency safe way. Blocking occurs at the expense
				of total performance of rendering all registered metrics. Ideally,
				Collector implementations support concurrent readers.

			( T) Desc() *Desc
				Desc returns the descriptor for the Metric. This method idempotently
				returns the same descriptor throughout the lifetime of the
				Metric. The returned descriptor is immutable by contract. A Metric
				unable to describe itself must return an invalid descriptor (created
				with NewInvalidDesc).

			( T) Describe(chan<- *Desc)
				Describe sends the super-set of all possible descriptors of metrics
				collected by this Collector to the provided channel and returns once
				the last descriptor has been sent. The sent descriptors fulfill the
				consistency and uniqueness requirements described in the Desc
				documentation.

				It is valid if one and the same Collector sends duplicate
				descriptors. Those duplicates are simply ignored. However, two
				different Collectors must not send duplicate descriptors.

				Sending no descriptor at all marks the Collector as “unchecked”,
				i.e. no checks will be performed at registration time, and the
				Collector may yield any Metric it sees fit in its Collect method.

				This method idempotently sends the same descriptors throughout the
				lifetime of the Collector. It may be called concurrently and
				therefore must be implemented in a concurrency safe way.

				If a Collector encounters an error while executing this method, it
				must send an invalid descriptor (created with NewInvalidDesc) to
				signal the error to the registry.

			( T) Write(*dto.Metric) error
				Write encodes the Metric into a "Metric" Protocol Buffer data
				transmission object.

				Metric implementations must observe concurrency safety as reads of
				this metric may occur at any time, and any blocking occurs at the
				expense of total performance of rendering all registered
				metrics. Ideally, Metric implementations should support concurrent
				readers.

				While populating dto.Metric, it is the responsibility of the
				implementation to ensure validity of the Metric protobuf (like valid
				UTF-8 strings or syntactically valid metric and label names). It is
				recommended to sort labels lexicographically. Callers of Write should
				still make sure of sorting if they depend on it.

		Implemented By (at least 12, in which 6 are exported)
			 Counter (interface)
			 Gauge (interface)
			 GaugeFunc (interface)
			 Histogram (interface)
			 Summary (interface)
			 UntypedFunc (interface)
			/* 6+ unexporteds ... *//* 6+ unexporteds: */
			*counter
			*gauge
			*histogram
			*noObjectivesSummary
			*summary
			*valueFunc
		Implements (at least 4, all are exported)
			 T : Collector
			 T : GaugeFunc
			 T : Metric
			 T : UntypedFunc
		As Outputs Of (at least one exported)
			func NewCounterFunc(opts CounterOpts, function func() float64) CounterFunc

	 type CounterOpts Opts (struct)
		CounterOpts is an alias for Opts. See there for doc comments.

		Fields (total 5, all are exported)
			ConstLabels Labels
				ConstLabels are used to attach fixed labels to this metric. Metrics
				with the same fully-qualified name must have the same label names in
				their ConstLabels.

				ConstLabels are only used rarely. In particular, do not use them to
				attach the same labels to all your metrics. Those use cases are
				better covered by target labels set by the scraping Prometheus
				server, or by one specific metric (e.g. a build_info or a
				machine_role metric). See also
				https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels,-not-static-scraped-labels

			Help string
				Help provides information about this metric.

				Metrics with the same fully-qualified name must have the same Help
				string.

			Name string
			Namespace string
				Namespace, Subsystem, and Name are components of the fully-qualified
				name of the Metric (created by joining these components with
				"_"). Only Name is mandatory, the others merely help structuring the
				name. Note that the fully-qualified name of the metric must be a
				valid Prometheus metric name.

			Subsystem string
		As Inputs Of (at least 3, all are exported)
			func NewCounter(opts CounterOpts) Counter
			func NewCounterFunc(opts CounterOpts, function func() float64) CounterFunc
			func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec

	 type CounterVec (struct)
		CounterVec is a Collector that bundles a set of Counters that all share the
		same Desc, but have different values for their variable labels. This is used
		if you want to count the same thing partitioned by various dimensions
		(e.g. number of HTTP requests, partitioned by response code and
		method). Create instances with NewCounterVec.

		Fields (total 9, none are exported)
			/* 9 unexporteds ... *//* 9 unexporteds: */
			metricVec *metricVec
			metricVec.curry []curriedLabelValue
			metricVec.hashAdd func(h uint64, s string) uint64
				hashAdd and hashAddByte can be replaced for testing collision handling.

			metricVec.hashAddByte func(h uint64, b byte) uint64
			metricVec.metricMap *metricMap
			metricVec.metricMap.desc *Desc
			metricVec.metricMap.metrics map[uint64][]metricWithLabelValues
			metricVec.metricMap.mtx sync.RWMutex
				// Protects metrics.

			metricVec.metricMap.newMetric func(labelValues ...string) Metric
		Methods (total 22, in which 11 are exported)
			( T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) CurryWith(labels Labels) (*CounterVec, error)
				CurryWith returns a vector curried with the provided labels, i.e. the
				returned vector has those labels pre-set for all labeled operations performed
				on it. The cardinality of the curried vector is reduced accordingly. The
				order of the remaining labels stays the same (just with the curried labels
				taken out of the sequence – which is relevant for the
				(GetMetric)WithLabelValues methods). It is possible to curry a curried
				vector, but only with labels not yet used for currying before.

				The metrics contained in the CounterVec are shared between the curried and
				uncurried vectors. They are just accessed differently. Curried and uncurried
				vectors behave identically in terms of collection. Only one must be
				registered with a given registry (usually the uncurried version). The Reset
				method deletes all metrics, even if called on a curried vector.

			( T) Delete(labels Labels) bool
				Delete deletes the metric where the variable labels are the same as those
				passed in as labels. It returns true if a metric was deleted.

				It is not an error if the number and names of the Labels are inconsistent
				with those of the VariableLabels in Desc. However, such inconsistent Labels
				can never match an actual metric, so the method will always return false in
				that case.

				This method is used for the same purpose as DeleteLabelValues(...string). See
				there for pros and cons of the two methods.

			( T) DeleteLabelValues(lvs ...string) bool
				DeleteLabelValues removes the metric where the variable labels are the same
				as those passed in as labels (same order as the VariableLabels in Desc). It
				returns true if a metric was deleted.

				It is not an error if the number of label values is not the same as the
				number of VariableLabels in Desc. However, such inconsistent label count can
				never match an actual metric, so the method will always return false in that
				case.

				Note that for more than one label value, this method is prone to mistakes
				caused by an incorrect order of arguments. Consider Delete(Labels) as an
				alternative to avoid that type of mistake. For higher label numbers, the
				latter has a much more readable (albeit more verbose) syntax, but it comes
				with a performance overhead (for creating and processing the Labels map).
				See also the CounterVec example.

			( T) Describe(ch chan<- *Desc)
				Describe implements Collector. It will send exactly one Desc to the provided
				channel.

			(*T) GetMetricWith(labels Labels) (Counter, error)
				GetMetricWith returns the Counter for the given Labels map (the label names
				must match those of the VariableLabels in Desc). If that label map is
				accessed for the first time, a new Counter is created. Implications of
				creating a Counter without using it and keeping the Counter for later use are
				the same as for GetMetricWithLabelValues.

				An error is returned if the number and names of the Labels are inconsistent
				with those of the VariableLabels in Desc (minus any curried labels).

				This method is used for the same purpose as
				GetMetricWithLabelValues(...string). See there for pros and cons of the two
				methods.

			(*T) GetMetricWithLabelValues(lvs ...string) (Counter, error)
				GetMetricWithLabelValues returns the Counter for the given slice of label
				values (same order as the VariableLabels in Desc). If that combination of
				label values is accessed for the first time, a new Counter is created.

				It is possible to call this method without using the returned Counter to only
				create the new Counter but leave it at its starting value 0. See also the
				SummaryVec example.

				Keeping the Counter for later use is possible (and should be considered if
				performance is critical), but keep in mind that Reset, DeleteLabelValues and
				Delete can be used to delete the Counter from the CounterVec. In that case,
				the Counter will still exist, but it will not be exported anymore, even if a
				Counter with the same label values is created later.

				An error is returned if the number of label values is not the same as the
				number of VariableLabels in Desc (minus any curried labels).

				Note that for more than one label value, this method is prone to mistakes
				caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
				an alternative to avoid that type of mistake. For higher label numbers, the
				latter has a much more readable (albeit more verbose) syntax, but it comes
				with a performance overhead (for creating and processing the Labels map).
				See also the GaugeVec example.

			(*T) MustCurryWith(labels Labels) *CounterVec
				MustCurryWith works as CurryWith but panics where CurryWith would have
				returned an error.

			( T) Reset()
				Reset deletes all metrics in this vector.

			(*T) With(labels Labels) Counter
				With works as GetMetricWith, but panics where GetMetricWithLabels would have
				returned an error. Not returning an error allows shortcuts like
				    myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Add(42)

			(*T) WithLabelValues(lvs ...string) Counter
				WithLabelValues works as GetMetricWithLabelValues, but panics where
				GetMetricWithLabelValues would have returned an error. Not returning an
				error allows shortcuts like
				    myVec.WithLabelValues("404", "GET").Add(42)

			/* 11 unexporteds ... *//* 11 unexporteds: */
			( T) curryWith(labels Labels) (*metricVec, error)
			( T) deleteByHashWithLabelValues(h uint64, lvs []string, curry []curriedLabelValue) bool
				deleteByHashWithLabelValues removes the metric from the hash bucket h. If
				there are multiple matches in the bucket, use lvs to select a metric and
				remove only that metric.

			( T) deleteByHashWithLabels(h uint64, labels Labels, curry []curriedLabelValue) bool
				deleteByHashWithLabels removes the metric from the hash bucket h. If there
				are multiple matches in the bucket, use lvs to select a metric and remove
				only that metric.

			( T) getMetricWith(labels Labels) (Metric, error)
			( T) getMetricWithHashAndLabelValues(h uint64, lvs []string, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabelValues gets a metric while handling possible
				collisions in the hash space. Must be called while holding the read mutex.

			( T) getMetricWithHashAndLabels(h uint64, labels Labels, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabels gets a metric while handling possible collisions in
				the hash space. Must be called while holding read mutex.

			( T) getMetricWithLabelValues(lvs ...string) (Metric, error)
			( T) getOrCreateMetricWithLabelValues(hash uint64, lvs []string, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			( T) getOrCreateMetricWithLabels(hash uint64, labels Labels, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			( T) hashLabelValues(vals []string) (uint64, error)
			( T) hashLabels(labels Labels) (uint64, error)
		Implements (at least one exported)
			 T : Collector
		As Outputs Of (at least 3, all are exported)
			func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec
			func (*CounterVec).CurryWith(labels Labels) (*CounterVec, error)
			func (*CounterVec).MustCurryWith(labels Labels) *CounterVec
		As Inputs Of (at least 2, both are exported)
			func github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerCounter(counter *CounterVec, next http.Handler) http.HandlerFunc
			func github.com/prometheus/client_golang/prometheus/promhttp.InstrumentRoundTripperCounter(counter *CounterVec, next http.RoundTripper) promhttp.RoundTripperFunc

	 type Desc (struct)
		Desc is the descriptor used by every Prometheus Metric. It is essentially
		the immutable meta-data of a Metric. The normal Metric implementations
		included in this package manage their Desc under the hood. Users only have to
		deal with Desc if they use advanced features like the ExpvarCollector or
		custom Collectors and Metrics.

		Descriptors registered with the same registry have to fulfill certain
		consistency and uniqueness criteria if they share the same fully-qualified
		name: They must have the same help string and the same label names (aka label
		dimensions) in each, constLabels and variableLabels, but they must differ in
		the values of the constLabels.

		Descriptors that share the same fully-qualified names and the same label
		values of their constLabels are considered equal.

		Use NewDesc to create new Desc instances.

		Fields (total 7, none are exported)
			/* 7 unexporteds ... *//* 7 unexporteds: */
			constLabelPairs []*dto.LabelPair
				constLabelPairs contains precalculated DTO label pairs based on
				the constant labels.

			dimHash uint64
				dimHash is a hash of the label names (preset and variable) and the
				Help string. Each Desc with the same fqName must have the same
				dimHash.

			err error
				err is an error that occurred during construction. It is reported on
				registration time.

			fqName string
				fqName has been built from Namespace, Subsystem, and Name.

			help string
				help provides some helpful information about this metric.

			id uint64
				id is a hash of the values of the ConstLabels and fqName. This
				must be unique among all registered descriptors and can therefore be
				used as an identifier of the descriptor.

			variableLabels []string
				VariableLabels contains names of labels for which the metric
				maintains variable values.

		Methods (only one, which is exported)
			(*T) String() string
		Implements (at least 4, in which 2 are exported)
			*T : expvar.Var
			*T : fmt.Stringer
			/* 2+ unexporteds ... *//* 2+ unexporteds: */
			*T : context.stringer
			*T : runtime.stringer
		As Outputs Of (at least 11, in which 10 are exported)
			func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *Desc
			func NewInvalidDesc(err error) *Desc
			func Counter.Desc() *Desc
			func CounterFunc.Desc() *Desc
			func Gauge.Desc() *Desc
			func GaugeFunc.Desc() *Desc
			func Histogram.Desc() *Desc
			func Metric.Desc() *Desc
			func Summary.Desc() *Desc
			func UntypedFunc.Desc() *Desc
			/* at least one unexported ... *//* at least one unexported: */
			func wrapDesc(desc *Desc, prefix string, labels Labels) *Desc
		As Inputs Of (at least 29, in which 18 are exported)
			func DescribeByCollect(c Collector, descs chan<- *Desc)
			func MustNewConstHistogram(desc *Desc, count uint64, sum float64, buckets map[float64]uint64, labelValues ...string) Metric
			func MustNewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) Metric
			func MustNewConstSummary(desc *Desc, count uint64, sum float64, quantiles map[float64]float64, labelValues ...string) Metric
			func NewConstHistogram(desc *Desc, count uint64, sum float64, buckets map[float64]uint64, labelValues ...string) (Metric, error)
			func NewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) (Metric, error)
			func NewConstSummary(desc *Desc, count uint64, sum float64, quantiles map[float64]float64, labelValues ...string) (Metric, error)
			func NewExpvarCollector(exports map[string]*Desc) Collector
			func NewInvalidMetric(desc *Desc, err error) Metric
			func Collector.Describe(chan<- *Desc)
			func Counter.Describe(chan<- *Desc)
			func CounterFunc.Describe(chan<- *Desc)
			func Gauge.Describe(chan<- *Desc)
			func GaugeFunc.Describe(chan<- *Desc)
			func Histogram.Describe(chan<- *Desc)
			func ObserverVec.Describe(chan<- *Desc)
			func Summary.Describe(chan<- *Desc)
			func UntypedFunc.Describe(chan<- *Desc)
			/* 11+ unexporteds ... *//* 11+ unexporteds: */
			func checkDescConsistency(metricFamily *dto.MetricFamily, dtoMetric *dto.Metric, desc *Desc) error
			func extractLabelValues(desc *Desc, labels Labels, curry []curriedLabelValue) []string
			func findMetricWithLabels(desc *Desc, metrics []metricWithLabelValues, labels Labels, curry []curriedLabelValue) int
			func makeLabelPairs(desc *Desc, labelValues []string) []*dto.LabelPair
			func matchLabels(desc *Desc, values []string, labels Labels, curry []curriedLabelValue) bool
			func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogram
			func newMetricVec(desc *Desc, newMetric func(lvs ...string) Metric) *metricVec
			func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary
			func newValueFunc(desc *Desc, valueType ValueType, function func() float64) *valueFunc
			func wrapDesc(desc *Desc, prefix string, labels Labels) *Desc
			func contrib.go.opencensus.io/exporter/prometheus.toPromMetric(desc *Desc, metric *metricdata.Metric, point metricdata.Point, labelValues []string) (Metric, error)

	 type Gatherer (interface)
		Gatherer is the interface for the part of a registry in charge of gathering
		the collected metrics into a number of MetricFamilies. The Gatherer interface
		comes with the same general implication as described for the Registerer
		interface.

		Methods (only one, which is exported)
			( T) Gather() ([]*dto.MetricFamily, error)
				Gather calls the Collect method of the registered Collectors and then
				gathers the collected metrics into a lexicographically sorted slice
				of uniquely named MetricFamily protobufs. Gather ensures that the
				returned slice is valid and self-consistent so that it can be used
				for valid exposition. As an exception to the strict consistency
				requirements described for metric.Desc, Gather will tolerate
				different sets of label names for metrics of the same metric family.

				Even if an error occurs, Gather attempts to gather as many metrics as
				possible. Hence, if a non-nil error is returned, the returned
				MetricFamily slice could be nil (in case of a fatal error that
				prevented any meaningful metric collection) or contain a number of
				MetricFamily protobufs, some of which might be incomplete, and some
				might be missing altogether. The returned error (which might be a
				MultiError) explains the details. Note that this is mostly useful for
				debugging purposes. If the gathered protobufs are to be used for
				exposition in actual monitoring, it is almost always better to not
				expose an incomplete result and instead disregard the returned
				MetricFamily protobufs in case the returned error is non-nil.

		Implemented By (at least 3, all are exported)
			 GathererFunc
			 Gatherers
			*Registry
		As Inputs Of (at least 2, both are exported)
			func WriteToTextfile(filename string, g Gatherer) error
			func github.com/prometheus/client_golang/prometheus/promhttp.HandlerFor(reg Gatherer, opts promhttp.HandlerOpts) http.Handler
		As Types Of (only one, which is exported)
			  var DefaultGatherer

	 type GathererFunc (func)
		GathererFunc turns a function into a Gatherer.

		Methods (only one, which is exported)
			( T) Gather() ([]*dto.MetricFamily, error)
				Gather implements Gatherer.

		Implements (at least one exported)
			 T : Gatherer

	 type Gatherers ([]T)
		Gatherers is a slice of Gatherer instances that implements the Gatherer
		interface itself. Its Gather method calls Gather on all Gatherers in the
		slice in order and returns the merged results. Errors returned from the
		Gather calls are all returned in a flattened MultiError. Duplicate and
		inconsistent Metrics are skipped (first occurrence in slice order wins) and
		reported in the returned error.

		Gatherers can be used to merge the Gather results from multiple
		Registries. It also provides a way to directly inject existing MetricFamily
		protobufs into the gathering by creating a custom Gatherer with a Gather
		method that simply returns the existing MetricFamily protobufs. Note that no
		registration is involved (in contrast to Collector registration), so
		obviously registration-time checks cannot happen. Any inconsistencies between
		the gathered MetricFamilies are reported as errors by the Gather method, and
		inconsistent Metrics are dropped. Invalid parts of the MetricFamilies
		(e.g. syntactically invalid metric or label names) will go undetected.

		Methods (only one, which is exported)
			( T) Gather() ([]*dto.MetricFamily, error)
				Gather implements Gatherer.

		Implements (at least one exported)
			 T : Gatherer

	 type Gauge (interface)
		Gauge is a Metric that represents a single numerical value that can
		arbitrarily go up and down.

		A Gauge is typically used for measured values like temperatures or current
		memory usage, but also "counts" that can go up and down, like the number of
		running goroutines.

		To create Gauge instances, use NewGauge.

		Methods (total 10, all are exported)
			( T) Add(float64)
				Add adds the given value to the Gauge. (The value can be negative,
				resulting in a decrease of the Gauge.)

			( T) Collect(chan<- Metric)
				Collect is called by the Prometheus registry when collecting
				metrics. The implementation sends each collected metric via the
				provided channel and returns once the last metric has been sent. The
				descriptor of each sent metric is one of those returned by Describe
				(unless the Collector is unchecked, see above). Returned metrics that
				share the same descriptor must differ in their variable label
				values.

				This method may be called concurrently and must therefore be
				implemented in a concurrency safe way. Blocking occurs at the expense
				of total performance of rendering all registered metrics. Ideally,
				Collector implementations support concurrent readers.

			( T) Dec()
				Dec decrements the Gauge by 1. Use Sub to decrement it by arbitrary
				values.

			( T) Desc() *Desc
				Desc returns the descriptor for the Metric. This method idempotently
				returns the same descriptor throughout the lifetime of the
				Metric. The returned descriptor is immutable by contract. A Metric
				unable to describe itself must return an invalid descriptor (created
				with NewInvalidDesc).

			( T) Describe(chan<- *Desc)
				Describe sends the super-set of all possible descriptors of metrics
				collected by this Collector to the provided channel and returns once
				the last descriptor has been sent. The sent descriptors fulfill the
				consistency and uniqueness requirements described in the Desc
				documentation.

				It is valid if one and the same Collector sends duplicate
				descriptors. Those duplicates are simply ignored. However, two
				different Collectors must not send duplicate descriptors.

				Sending no descriptor at all marks the Collector as “unchecked”,
				i.e. no checks will be performed at registration time, and the
				Collector may yield any Metric it sees fit in its Collect method.

				This method idempotently sends the same descriptors throughout the
				lifetime of the Collector. It may be called concurrently and
				therefore must be implemented in a concurrency safe way.

				If a Collector encounters an error while executing this method, it
				must send an invalid descriptor (created with NewInvalidDesc) to
				signal the error to the registry.

			( T) Inc()
				Inc increments the Gauge by 1. Use Add to increment it by arbitrary
				values.

			( T) Set(float64)
				Set sets the Gauge to an arbitrary value.

			( T) SetToCurrentTime()
				SetToCurrentTime sets the Gauge to the current Unix time in seconds.

			( T) Sub(float64)
				Sub subtracts the given value from the Gauge. (The value can be
				negative, resulting in an increase of the Gauge.)

			( T) Write(*dto.Metric) error
				Write encodes the Metric into a "Metric" Protocol Buffer data
				transmission object.

				Metric implementations must observe concurrency safety as reads of
				this metric may occur at any time, and any blocking occurs at the
				expense of total performance of rendering all registered
				metrics. Ideally, Metric implementations should support concurrent
				readers.

				While populating dto.Metric, it is the responsibility of the
				implementation to ensure validity of the Metric protobuf (like valid
				UTF-8 strings or syntactically valid metric and label names). It is
				recommended to sort labels lexicographically. Callers of Write should
				still make sure of sorting if they depend on it.

		Implemented By (at least one unexported)
			/* at least one unexported ... *//* at least one unexported: */
			*gauge
		Implements (at least 6, all are exported)
			 T : Collector
			 T : Counter
			 T : CounterFunc
			 T : GaugeFunc
			 T : Metric
			 T : UntypedFunc
		As Outputs Of (at least 5, all are exported)
			func NewGauge(opts GaugeOpts) Gauge
			func (*GaugeVec).GetMetricWith(labels Labels) (Gauge, error)
			func (*GaugeVec).GetMetricWithLabelValues(lvs ...string) (Gauge, error)
			func (*GaugeVec).With(labels Labels) Gauge
			func (*GaugeVec).WithLabelValues(lvs ...string) Gauge
		As Inputs Of (at least 2, both are exported)
			func github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerInFlight(g Gauge, next http.Handler) http.Handler
			func github.com/prometheus/client_golang/prometheus/promhttp.InstrumentRoundTripperInFlight(gauge Gauge, next http.RoundTripper) promhttp.RoundTripperFunc

	 type GaugeFunc (interface)
		GaugeFunc is a Gauge whose value is determined at collect time by calling a
		provided function.

		To create GaugeFunc instances, use NewGaugeFunc.

		Methods (total 4, all are exported)
			( T) Collect(chan<- Metric)
				Collect is called by the Prometheus registry when collecting
				metrics. The implementation sends each collected metric via the
				provided channel and returns once the last metric has been sent. The
				descriptor of each sent metric is one of those returned by Describe
				(unless the Collector is unchecked, see above). Returned metrics that
				share the same descriptor must differ in their variable label
				values.

				This method may be called concurrently and must therefore be
				implemented in a concurrency safe way. Blocking occurs at the expense
				of total performance of rendering all registered metrics. Ideally,
				Collector implementations support concurrent readers.

			( T) Desc() *Desc
				Desc returns the descriptor for the Metric. This method idempotently
				returns the same descriptor throughout the lifetime of the
				Metric. The returned descriptor is immutable by contract. A Metric
				unable to describe itself must return an invalid descriptor (created
				with NewInvalidDesc).

			( T) Describe(chan<- *Desc)
				Describe sends the super-set of all possible descriptors of metrics
				collected by this Collector to the provided channel and returns once
				the last descriptor has been sent. The sent descriptors fulfill the
				consistency and uniqueness requirements described in the Desc
				documentation.

				It is valid if one and the same Collector sends duplicate
				descriptors. Those duplicates are simply ignored. However, two
				different Collectors must not send duplicate descriptors.

				Sending no descriptor at all marks the Collector as “unchecked”,
				i.e. no checks will be performed at registration time, and the
				Collector may yield any Metric it sees fit in its Collect method.

				This method idempotently sends the same descriptors throughout the
				lifetime of the Collector. It may be called concurrently and
				therefore must be implemented in a concurrency safe way.

				If a Collector encounters an error while executing this method, it
				must send an invalid descriptor (created with NewInvalidDesc) to
				signal the error to the registry.

			( T) Write(*dto.Metric) error
				Write encodes the Metric into a "Metric" Protocol Buffer data
				transmission object.

				Metric implementations must observe concurrency safety as reads of
				this metric may occur at any time, and any blocking occurs at the
				expense of total performance of rendering all registered
				metrics. Ideally, Metric implementations should support concurrent
				readers.

				While populating dto.Metric, it is the responsibility of the
				implementation to ensure validity of the Metric protobuf (like valid
				UTF-8 strings or syntactically valid metric and label names). It is
				recommended to sort labels lexicographically. Callers of Write should
				still make sure of sorting if they depend on it.

		Implemented By (at least 12, in which 6 are exported)
			 Counter (interface)
			 CounterFunc (interface)
			 Gauge (interface)
			 Histogram (interface)
			 Summary (interface)
			 UntypedFunc (interface)
			/* 6+ unexporteds ... *//* 6+ unexporteds: */
			*counter
			*gauge
			*histogram
			*noObjectivesSummary
			*summary
			*valueFunc
		Implements (at least 4, all are exported)
			 T : Collector
			 T : CounterFunc
			 T : Metric
			 T : UntypedFunc
		As Outputs Of (at least one exported)
			func NewGaugeFunc(opts GaugeOpts, function func() float64) GaugeFunc

	 type GaugeOpts Opts (struct)
		GaugeOpts is an alias for Opts. See there for doc comments.

		Fields (total 5, all are exported)
			ConstLabels Labels
				ConstLabels are used to attach fixed labels to this metric. Metrics
				with the same fully-qualified name must have the same label names in
				their ConstLabels.

				ConstLabels are only used rarely. In particular, do not use them to
				attach the same labels to all your metrics. Those use cases are
				better covered by target labels set by the scraping Prometheus
				server, or by one specific metric (e.g. a build_info or a
				machine_role metric). See also
				https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels,-not-static-scraped-labels

			Help string
				Help provides information about this metric.

				Metrics with the same fully-qualified name must have the same Help
				string.

			Name string
			Namespace string
				Namespace, Subsystem, and Name are components of the fully-qualified
				name of the Metric (created by joining these components with
				"_"). Only Name is mandatory, the others merely help structuring the
				name. Note that the fully-qualified name of the metric must be a
				valid Prometheus metric name.

			Subsystem string
		As Inputs Of (at least 3, all are exported)
			func NewGauge(opts GaugeOpts) Gauge
			func NewGaugeFunc(opts GaugeOpts, function func() float64) GaugeFunc
			func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec

	 type GaugeVec (struct)
		GaugeVec is a Collector that bundles a set of Gauges that all share the same
		Desc, but have different values for their variable labels. This is used if
		you want to count the same thing partitioned by various dimensions
		(e.g. number of operations queued, partitioned by user and operation
		type). Create instances with NewGaugeVec.

		Fields (total 9, none are exported)
			/* 9 unexporteds ... *//* 9 unexporteds: */
			metricVec *metricVec
			metricVec.curry []curriedLabelValue
			metricVec.hashAdd func(h uint64, s string) uint64
				hashAdd and hashAddByte can be replaced for testing collision handling.

			metricVec.hashAddByte func(h uint64, b byte) uint64
			metricVec.metricMap *metricMap
			metricVec.metricMap.desc *Desc
			metricVec.metricMap.metrics map[uint64][]metricWithLabelValues
			metricVec.metricMap.mtx sync.RWMutex
				// Protects metrics.

			metricVec.metricMap.newMetric func(labelValues ...string) Metric
		Methods (total 22, in which 11 are exported)
			( T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) CurryWith(labels Labels) (*GaugeVec, error)
				CurryWith returns a vector curried with the provided labels, i.e. the
				returned vector has those labels pre-set for all labeled operations performed
				on it. The cardinality of the curried vector is reduced accordingly. The
				order of the remaining labels stays the same (just with the curried labels
				taken out of the sequence – which is relevant for the
				(GetMetric)WithLabelValues methods). It is possible to curry a curried
				vector, but only with labels not yet used for currying before.

				The metrics contained in the GaugeVec are shared between the curried and
				uncurried vectors. They are just accessed differently. Curried and uncurried
				vectors behave identically in terms of collection. Only one must be
				registered with a given registry (usually the uncurried version). The Reset
				method deletes all metrics, even if called on a curried vector.

			( T) Delete(labels Labels) bool
				Delete deletes the metric where the variable labels are the same as those
				passed in as labels. It returns true if a metric was deleted.

				It is not an error if the number and names of the Labels are inconsistent
				with those of the VariableLabels in Desc. However, such inconsistent Labels
				can never match an actual metric, so the method will always return false in
				that case.

				This method is used for the same purpose as DeleteLabelValues(...string). See
				there for pros and cons of the two methods.

			( T) DeleteLabelValues(lvs ...string) bool
				DeleteLabelValues removes the metric where the variable labels are the same
				as those passed in as labels (same order as the VariableLabels in Desc). It
				returns true if a metric was deleted.

				It is not an error if the number of label values is not the same as the
				number of VariableLabels in Desc. However, such inconsistent label count can
				never match an actual metric, so the method will always return false in that
				case.

				Note that for more than one label value, this method is prone to mistakes
				caused by an incorrect order of arguments. Consider Delete(Labels) as an
				alternative to avoid that type of mistake. For higher label numbers, the
				latter has a much more readable (albeit more verbose) syntax, but it comes
				with a performance overhead (for creating and processing the Labels map).
				See also the CounterVec example.

			( T) Describe(ch chan<- *Desc)
				Describe implements Collector. It will send exactly one Desc to the provided
				channel.

			(*T) GetMetricWith(labels Labels) (Gauge, error)
				GetMetricWith returns the Gauge for the given Labels map (the label names
				must match those of the VariableLabels in Desc). If that label map is
				accessed for the first time, a new Gauge is created. Implications of
				creating a Gauge without using it and keeping the Gauge for later use are
				the same as for GetMetricWithLabelValues.

				An error is returned if the number and names of the Labels are inconsistent
				with those of the VariableLabels in Desc (minus any curried labels).

				This method is used for the same purpose as
				GetMetricWithLabelValues(...string). See there for pros and cons of the two
				methods.

			(*T) GetMetricWithLabelValues(lvs ...string) (Gauge, error)
				GetMetricWithLabelValues returns the Gauge for the given slice of label
				values (same order as the VariableLabels in Desc). If that combination of
				label values is accessed for the first time, a new Gauge is created.

				It is possible to call this method without using the returned Gauge to only
				create the new Gauge but leave it at its starting value 0. See also the
				SummaryVec example.

				Keeping the Gauge for later use is possible (and should be considered if
				performance is critical), but keep in mind that Reset, DeleteLabelValues and
				Delete can be used to delete the Gauge from the GaugeVec. In that case, the
				Gauge will still exist, but it will not be exported anymore, even if a
				Gauge with the same label values is created later. See also the CounterVec
				example.

				An error is returned if the number of label values is not the same as the
				number of VariableLabels in Desc (minus any curried labels).

				Note that for more than one label value, this method is prone to mistakes
				caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
				an alternative to avoid that type of mistake. For higher label numbers, the
				latter has a much more readable (albeit more verbose) syntax, but it comes
				with a performance overhead (for creating and processing the Labels map).

			(*T) MustCurryWith(labels Labels) *GaugeVec
				MustCurryWith works as CurryWith but panics where CurryWith would have
				returned an error.

			( T) Reset()
				Reset deletes all metrics in this vector.

			(*T) With(labels Labels) Gauge
				With works as GetMetricWith, but panics where GetMetricWithLabels would have
				returned an error. Not returning an error allows shortcuts like
				    myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Add(42)

			(*T) WithLabelValues(lvs ...string) Gauge
				WithLabelValues works as GetMetricWithLabelValues, but panics where
				GetMetricWithLabelValues would have returned an error. Not returning an
				error allows shortcuts like
				    myVec.WithLabelValues("404", "GET").Add(42)

			/* 11 unexporteds ... *//* 11 unexporteds: */
			( T) curryWith(labels Labels) (*metricVec, error)
			( T) deleteByHashWithLabelValues(h uint64, lvs []string, curry []curriedLabelValue) bool
				deleteByHashWithLabelValues removes the metric from the hash bucket h. If
				there are multiple matches in the bucket, use lvs to select a metric and
				remove only that metric.

			( T) deleteByHashWithLabels(h uint64, labels Labels, curry []curriedLabelValue) bool
				deleteByHashWithLabels removes the metric from the hash bucket h. If there
				are multiple matches in the bucket, use lvs to select a metric and remove
				only that metric.

			( T) getMetricWith(labels Labels) (Metric, error)
			( T) getMetricWithHashAndLabelValues(h uint64, lvs []string, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabelValues gets a metric while handling possible
				collisions in the hash space. Must be called while holding the read mutex.

			( T) getMetricWithHashAndLabels(h uint64, labels Labels, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabels gets a metric while handling possible collisions in
				the hash space. Must be called while holding read mutex.

			( T) getMetricWithLabelValues(lvs ...string) (Metric, error)
			( T) getOrCreateMetricWithLabelValues(hash uint64, lvs []string, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			( T) getOrCreateMetricWithLabels(hash uint64, labels Labels, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			( T) hashLabelValues(vals []string) (uint64, error)
			( T) hashLabels(labels Labels) (uint64, error)
		Implements (at least one exported)
			 T : Collector
		As Outputs Of (at least 3, all are exported)
			func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec
			func (*GaugeVec).CurryWith(labels Labels) (*GaugeVec, error)
			func (*GaugeVec).MustCurryWith(labels Labels) *GaugeVec

	 type Histogram (interface)
		A Histogram counts individual observations from an event or sample stream in
		configurable buckets. Similar to a summary, it also provides a sum of
		observations and an observation count.

		On the Prometheus server, quantiles can be calculated from a Histogram using
		the histogram_quantile function in the query language.

		Note that Histograms, in contrast to Summaries, can be aggregated with the
		Prometheus query language (see the documentation for detailed
		procedures). However, Histograms require the user to pre-define suitable
		buckets, and they are in general less accurate. The Observe method of a
		Histogram has a very low performance overhead in comparison with the Observe
		method of a Summary.

		To create Histogram instances, use NewHistogram.

		Methods (total 5, all are exported)
			( T) Collect(chan<- Metric)
				Collect is called by the Prometheus registry when collecting
				metrics. The implementation sends each collected metric via the
				provided channel and returns once the last metric has been sent. The
				descriptor of each sent metric is one of those returned by Describe
				(unless the Collector is unchecked, see above). Returned metrics that
				share the same descriptor must differ in their variable label
				values.

				This method may be called concurrently and must therefore be
				implemented in a concurrency safe way. Blocking occurs at the expense
				of total performance of rendering all registered metrics. Ideally,
				Collector implementations support concurrent readers.

			( T) Desc() *Desc
				Desc returns the descriptor for the Metric. This method idempotently
				returns the same descriptor throughout the lifetime of the
				Metric. The returned descriptor is immutable by contract. A Metric
				unable to describe itself must return an invalid descriptor (created
				with NewInvalidDesc).

			( T) Describe(chan<- *Desc)
				Describe sends the super-set of all possible descriptors of metrics
				collected by this Collector to the provided channel and returns once
				the last descriptor has been sent. The sent descriptors fulfill the
				consistency and uniqueness requirements described in the Desc
				documentation.

				It is valid if one and the same Collector sends duplicate
				descriptors. Those duplicates are simply ignored. However, two
				different Collectors must not send duplicate descriptors.

				Sending no descriptor at all marks the Collector as “unchecked”,
				i.e. no checks will be performed at registration time, and the
				Collector may yield any Metric it sees fit in its Collect method.

				This method idempotently sends the same descriptors throughout the
				lifetime of the Collector. It may be called concurrently and
				therefore must be implemented in a concurrency safe way.

				If a Collector encounters an error while executing this method, it
				must send an invalid descriptor (created with NewInvalidDesc) to
				signal the error to the registry.

			( T) Observe(float64)
				Observe adds a single observation to the histogram.

			( T) Write(*dto.Metric) error
				Write encodes the Metric into a "Metric" Protocol Buffer data
				transmission object.

				Metric implementations must observe concurrency safety as reads of
				this metric may occur at any time, and any blocking occurs at the
				expense of total performance of rendering all registered
				metrics. Ideally, Metric implementations should support concurrent
				readers.

				While populating dto.Metric, it is the responsibility of the
				implementation to ensure validity of the Metric protobuf (like valid
				UTF-8 strings or syntactically valid metric and label names). It is
				recommended to sort labels lexicographically. Callers of Write should
				still make sure of sorting if they depend on it.

		Implemented By (at least 4, in which 1 are exported)
			 Summary (interface)
			/* 3+ unexporteds ... *//* 3+ unexporteds: */
			*histogram
			*noObjectivesSummary
			*summary
		Implements (at least 7, all are exported)
			 T : Collector
			 T : CounterFunc
			 T : GaugeFunc
			 T : Metric
			 T : Observer
			 T : Summary
			 T : UntypedFunc
		As Outputs Of (at least 2, in which 1 are exported)
			func NewHistogram(opts HistogramOpts) Histogram
			/* at least one unexported ... *//* at least one unexported: */
			func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogram

	 type HistogramOpts (struct)
		HistogramOpts bundles the options for creating a Histogram metric. It is
		mandatory to set Name to a non-empty string. All other fields are optional
		and can safely be left at their zero value, although it is strongly
		encouraged to set a Help string.

		Fields (total 6, all are exported)
			Buckets []float64
				Buckets defines the buckets into which observations are counted. Each
				element in the slice is the upper inclusive bound of a bucket. The
				values must be sorted in strictly increasing order. There is no need
				to add a highest bucket with +Inf bound, it will be added
				implicitly. The default value is DefBuckets.

			ConstLabels Labels
				ConstLabels are used to attach fixed labels to this metric. Metrics
				with the same fully-qualified name must have the same label names in
				their ConstLabels.

				ConstLabels are only used rarely. In particular, do not use them to
				attach the same labels to all your metrics. Those use cases are
				better covered by target labels set by the scraping Prometheus
				server, or by one specific metric (e.g. a build_info or a
				machine_role metric). See also
				https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels-not-static-scraped-labels

			Help string
				Help provides information about this Histogram.

				Metrics with the same fully-qualified name must have the same Help
				string.

			Name string
			Namespace string
				Namespace, Subsystem, and Name are components of the fully-qualified
				name of the Histogram (created by joining these components with
				"_"). Only Name is mandatory, the others merely help structuring the
				name. Note that the fully-qualified name of the Histogram must be a
				valid Prometheus metric name.

			Subsystem string
		As Inputs Of (at least 3, in which 2 are exported)
			func NewHistogram(opts HistogramOpts) Histogram
			func NewHistogramVec(opts HistogramOpts, labelNames []string) *HistogramVec
			/* at least one unexported ... *//* at least one unexported: */
			func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogram

	 type HistogramVec (struct)
		HistogramVec is a Collector that bundles a set of Histograms that all share the
		same Desc, but have different values for their variable labels. This is used
		if you want to count the same thing partitioned by various dimensions
		(e.g. HTTP request latencies, partitioned by status code and method). Create
		instances with NewHistogramVec.

		Fields (total 9, none are exported)
			/* 9 unexporteds ... *//* 9 unexporteds: */
			metricVec *metricVec
			metricVec.curry []curriedLabelValue
			metricVec.hashAdd func(h uint64, s string) uint64
				hashAdd and hashAddByte can be replaced for testing collision handling.

			metricVec.hashAddByte func(h uint64, b byte) uint64
			metricVec.metricMap *metricMap
			metricVec.metricMap.desc *Desc
			metricVec.metricMap.metrics map[uint64][]metricWithLabelValues
			metricVec.metricMap.mtx sync.RWMutex
				// Protects metrics.

			metricVec.metricMap.newMetric func(labelValues ...string) Metric
		Methods (total 22, in which 11 are exported)
			( T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) CurryWith(labels Labels) (ObserverVec, error)
				CurryWith returns a vector curried with the provided labels, i.e. the
				returned vector has those labels pre-set for all labeled operations performed
				on it. The cardinality of the curried vector is reduced accordingly. The
				order of the remaining labels stays the same (just with the curried labels
				taken out of the sequence – which is relevant for the
				(GetMetric)WithLabelValues methods). It is possible to curry a curried
				vector, but only with labels not yet used for currying before.

				The metrics contained in the HistogramVec are shared between the curried and
				uncurried vectors. They are just accessed differently. Curried and uncurried
				vectors behave identically in terms of collection. Only one must be
				registered with a given registry (usually the uncurried version). The Reset
				method deletes all metrics, even if called on a curried vector.

			( T) Delete(labels Labels) bool
				Delete deletes the metric where the variable labels are the same as those
				passed in as labels. It returns true if a metric was deleted.

				It is not an error if the number and names of the Labels are inconsistent
				with those of the VariableLabels in Desc. However, such inconsistent Labels
				can never match an actual metric, so the method will always return false in
				that case.

				This method is used for the same purpose as DeleteLabelValues(...string). See
				there for pros and cons of the two methods.

			( T) DeleteLabelValues(lvs ...string) bool
				DeleteLabelValues removes the metric where the variable labels are the same
				as those passed in as labels (same order as the VariableLabels in Desc). It
				returns true if a metric was deleted.

				It is not an error if the number of label values is not the same as the
				number of VariableLabels in Desc. However, such inconsistent label count can
				never match an actual metric, so the method will always return false in that
				case.

				Note that for more than one label value, this method is prone to mistakes
				caused by an incorrect order of arguments. Consider Delete(Labels) as an
				alternative to avoid that type of mistake. For higher label numbers, the
				latter has a much more readable (albeit more verbose) syntax, but it comes
				with a performance overhead (for creating and processing the Labels map).
				See also the CounterVec example.

			( T) Describe(ch chan<- *Desc)
				Describe implements Collector. It will send exactly one Desc to the provided
				channel.

			(*T) GetMetricWith(labels Labels) (Observer, error)
				GetMetricWith returns the Histogram for the given Labels map (the label names
				must match those of the VariableLabels in Desc). If that label map is
				accessed for the first time, a new Histogram is created. Implications of
				creating a Histogram without using it and keeping the Histogram for later use
				are the same as for GetMetricWithLabelValues.

				An error is returned if the number and names of the Labels are inconsistent
				with those of the VariableLabels in Desc (minus any curried labels).

				This method is used for the same purpose as
				GetMetricWithLabelValues(...string). See there for pros and cons of the two
				methods.

			(*T) GetMetricWithLabelValues(lvs ...string) (Observer, error)
				GetMetricWithLabelValues returns the Histogram for the given slice of label
				values (same order as the VariableLabels in Desc). If that combination of
				label values is accessed for the first time, a new Histogram is created.

				It is possible to call this method without using the returned Histogram to only
				create the new Histogram but leave it at its starting value, a Histogram without
				any observations.

				Keeping the Histogram for later use is possible (and should be considered if
				performance is critical), but keep in mind that Reset, DeleteLabelValues and
				Delete can be used to delete the Histogram from the HistogramVec. In that case, the
				Histogram will still exist, but it will not be exported anymore, even if a
				Histogram with the same label values is created later. See also the CounterVec
				example.

				An error is returned if the number of label values is not the same as the
				number of VariableLabels in Desc (minus any curried labels).

				Note that for more than one label value, this method is prone to mistakes
				caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
				an alternative to avoid that type of mistake. For higher label numbers, the
				latter has a much more readable (albeit more verbose) syntax, but it comes
				with a performance overhead (for creating and processing the Labels map).
				See also the GaugeVec example.

			(*T) MustCurryWith(labels Labels) ObserverVec
				MustCurryWith works as CurryWith but panics where CurryWith would have
				returned an error.

			( T) Reset()
				Reset deletes all metrics in this vector.

			(*T) With(labels Labels) Observer
				With works as GetMetricWith but panics where GetMetricWithLabels would have
				returned an error. Not returning an error allows shortcuts like
				    myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Observe(42.21)

			(*T) WithLabelValues(lvs ...string) Observer
				WithLabelValues works as GetMetricWithLabelValues, but panics where
				GetMetricWithLabelValues would have returned an error. Not returning an
				error allows shortcuts like
				    myVec.WithLabelValues("404", "GET").Observe(42.21)

			/* 11 unexporteds ... *//* 11 unexporteds: */
			( T) curryWith(labels Labels) (*metricVec, error)
			( T) deleteByHashWithLabelValues(h uint64, lvs []string, curry []curriedLabelValue) bool
				deleteByHashWithLabelValues removes the metric from the hash bucket h. If
				there are multiple matches in the bucket, use lvs to select a metric and
				remove only that metric.

			( T) deleteByHashWithLabels(h uint64, labels Labels, curry []curriedLabelValue) bool
				deleteByHashWithLabels removes the metric from the hash bucket h. If there
				are multiple matches in the bucket, use lvs to select a metric and remove
				only that metric.

			( T) getMetricWith(labels Labels) (Metric, error)
			( T) getMetricWithHashAndLabelValues(h uint64, lvs []string, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabelValues gets a metric while handling possible
				collisions in the hash space. Must be called while holding the read mutex.

			( T) getMetricWithHashAndLabels(h uint64, labels Labels, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabels gets a metric while handling possible collisions in
				the hash space. Must be called while holding read mutex.

			( T) getMetricWithLabelValues(lvs ...string) (Metric, error)
			( T) getOrCreateMetricWithLabelValues(hash uint64, lvs []string, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			( T) getOrCreateMetricWithLabels(hash uint64, labels Labels, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			( T) hashLabelValues(vals []string) (uint64, error)
			( T) hashLabels(labels Labels) (uint64, error)
		Implements (at least 2, both are exported)
			 T : Collector
			*T : ObserverVec
		As Outputs Of (at least one exported)
			func NewHistogramVec(opts HistogramOpts, labelNames []string) *HistogramVec

	 type Labels (map)
		Labels represents a collection of label name -> value mappings. This type is
		commonly used with the With(Labels) and GetMetricWith(Labels) methods of
		metric vector Collectors, e.g.:
		    myVec.With(Labels{"code": "404", "method": "GET"}).Add(42)

		The other use-case is the specification of constant label pairs in Opts or to
		create a Desc.

		As Outputs Of (at least one unexported)
			/* at least one unexported ... *//* at least one unexported: */
			func github.com/prometheus/client_golang/prometheus/promhttp.labels(code, method bool, reqMethod string, status int) Labels
		As Inputs Of (at least 27, in which 22 are exported)
			func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *Desc
			func WrapRegistererWith(labels Labels, reg Registerer) Registerer
			func (*CounterVec).CurryWith(labels Labels) (*CounterVec, error)
			func (*CounterVec).GetMetricWith(labels Labels) (Counter, error)
			func (*CounterVec).MustCurryWith(labels Labels) *CounterVec
			func (*CounterVec).With(labels Labels) Counter
			func (*GaugeVec).CurryWith(labels Labels) (*GaugeVec, error)
			func (*GaugeVec).GetMetricWith(labels Labels) (Gauge, error)
			func (*GaugeVec).MustCurryWith(labels Labels) *GaugeVec
			func (*GaugeVec).With(labels Labels) Gauge
			func (*HistogramVec).CurryWith(labels Labels) (ObserverVec, error)
			func (*HistogramVec).GetMetricWith(labels Labels) (Observer, error)
			func (*HistogramVec).MustCurryWith(labels Labels) ObserverVec
			func (*HistogramVec).With(labels Labels) Observer
			func ObserverVec.CurryWith(Labels) (ObserverVec, error)
			func ObserverVec.GetMetricWith(Labels) (Observer, error)
			func ObserverVec.MustCurryWith(Labels) ObserverVec
			func ObserverVec.With(Labels) Observer
			func (*SummaryVec).CurryWith(labels Labels) (ObserverVec, error)
			func (*SummaryVec).GetMetricWith(labels Labels) (Observer, error)
			func (*SummaryVec).MustCurryWith(labels Labels) ObserverVec
			func (*SummaryVec).With(labels Labels) Observer
			/* 5+ unexporteds ... *//* 5+ unexporteds: */
			func extractLabelValues(desc *Desc, labels Labels, curry []curriedLabelValue) []string
			func findMetricWithLabels(desc *Desc, metrics []metricWithLabelValues, labels Labels, curry []curriedLabelValue) int
			func matchLabels(desc *Desc, values []string, labels Labels, curry []curriedLabelValue) bool
			func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error
			func wrapDesc(desc *Desc, prefix string, labels Labels) *Desc
		As Types Of (only one, which is unexported)
			/* one unexported ... *//* one unexported: */
			  var github.com/prometheus/client_golang/prometheus/promhttp.emptyLabels

	 type Metric (interface)
		A Metric models a single sample value with its meta data being exported to
		Prometheus. Implementations of Metric in this package are Gauge, Counter,
		Histogram, Summary, and Untyped.

		Methods (total 2, both are exported)
			( T) Desc() *Desc
				Desc returns the descriptor for the Metric. This method idempotently
				returns the same descriptor throughout the lifetime of the
				Metric. The returned descriptor is immutable by contract. A Metric
				unable to describe itself must return an invalid descriptor (created
				with NewInvalidDesc).

			( T) Write(*dto.Metric) error
				Write encodes the Metric into a "Metric" Protocol Buffer data
				transmission object.

				Metric implementations must observe concurrency safety as reads of
				this metric may occur at any time, and any blocking occurs at the
				expense of total performance of rendering all registered
				metrics. Ideally, Metric implementations should support concurrent
				readers.

				While populating dto.Metric, it is the responsibility of the
				implementation to ensure validity of the Metric protobuf (like valid
				UTF-8 strings or syntactically valid metric and label names). It is
				recommended to sort labels lexicographically. Callers of Write should
				still make sure of sorting if they depend on it.

		Implemented By (at least 19, in which 7 are exported)
			 Counter (interface)
			 CounterFunc (interface)
			 Gauge (interface)
			 GaugeFunc (interface)
			 Histogram (interface)
			 Summary (interface)
			 UntypedFunc (interface)
			/* 12+ unexporteds ... *//* 12+ unexporteds: */
			*constHistogram
			*constMetric
			*constSummary
			*counter
			*gauge
			*histogram
			*invalidMetric
			*noObjectivesSummary
			*summary
			 timestampedMetric
			*valueFunc
			*wrappingMetric
		As Outputs Of (at least 9, in which 8 are exported)
			func MustNewConstHistogram(desc *Desc, count uint64, sum float64, buckets map[float64]uint64, labelValues ...string) Metric
			func MustNewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) Metric
			func MustNewConstSummary(desc *Desc, count uint64, sum float64, quantiles map[float64]float64, labelValues ...string) Metric
			func NewConstHistogram(desc *Desc, count uint64, sum float64, buckets map[float64]uint64, labelValues ...string) (Metric, error)
			func NewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) (Metric, error)
			func NewConstSummary(desc *Desc, count uint64, sum float64, quantiles map[float64]float64, labelValues ...string) (Metric, error)
			func NewInvalidMetric(desc *Desc, err error) Metric
			func NewMetricWithTimestamp(t time.Time, m Metric) Metric
			/* at least one unexported ... *//* at least one unexported: */
			func contrib.go.opencensus.io/exporter/prometheus.toPromMetric(desc *Desc, metric *metricdata.Metric, point metricdata.Point, labelValues []string) (Metric, error)
		As Inputs Of (at least 11, in which 10 are exported)
			func NewMetricWithTimestamp(t time.Time, m Metric) Metric
			func Collector.Collect(chan<- Metric)
			func Counter.Collect(chan<- Metric)
			func CounterFunc.Collect(chan<- Metric)
			func Gauge.Collect(chan<- Metric)
			func GaugeFunc.Collect(chan<- Metric)
			func Histogram.Collect(chan<- Metric)
			func ObserverVec.Collect(chan<- Metric)
			func Summary.Collect(chan<- Metric)
			func UntypedFunc.Collect(chan<- Metric)
			/* at least one unexported ... *//* at least one unexported: */
			func processMetric(metric Metric, metricFamiliesByName map[string]*dto.MetricFamily, metricHashes map[uint64]struct{}, registeredDescIDs map[uint64]struct{}) error

	 type MultiError ([]T)
		MultiError is a slice of errors implementing the error interface. It is used
		by a Gatherer to report multiple errors during MetricFamily gathering.

		Methods (total 3, all are exported)
			(*T) Append(err error)
				Append appends the provided error if it is not nil.

			( T) Error() string
			( T) MaybeUnwrap() error
				MaybeUnwrap returns nil if len(errs) is 0. It returns the first and only
				contained error as error if len(errs is 1). In all other cases, it returns
				the MultiError directly. This is helpful for returning a MultiError in a way
				that only uses the MultiError if needed.

		Implements (at least one exported)
			 T : error

	 type Observer (interface)
		Observer is the interface that wraps the Observe method, which is used by
		Histogram and Summary to add observations.

		Methods (only one, which is exported)
			( T) Observe(float64)
		Implemented By (at least 6, in which 3 are exported)
			 Histogram (interface)
			 ObserverFunc
			 Summary (interface)
			/* 3+ unexporteds ... *//* 3+ unexporteds: */
			*histogram
			*noObjectivesSummary
			*summary
		As Outputs Of (at least 12, all are exported)
			func (*HistogramVec).GetMetricWith(labels Labels) (Observer, error)
			func (*HistogramVec).GetMetricWithLabelValues(lvs ...string) (Observer, error)
			func (*HistogramVec).With(labels Labels) Observer
			func (*HistogramVec).WithLabelValues(lvs ...string) Observer
			func ObserverVec.GetMetricWith(Labels) (Observer, error)
			func ObserverVec.GetMetricWithLabelValues(lvs ...string) (Observer, error)
			func ObserverVec.With(Labels) Observer
			func ObserverVec.WithLabelValues(...string) Observer
			func (*SummaryVec).GetMetricWith(labels Labels) (Observer, error)
			func (*SummaryVec).GetMetricWithLabelValues(lvs ...string) (Observer, error)
			func (*SummaryVec).With(labels Labels) Observer
			func (*SummaryVec).WithLabelValues(lvs ...string) Observer
		As Inputs Of (at least one exported)
			func NewTimer(o Observer) *Timer

	 type ObserverFunc (func)
		The ObserverFunc type is an adapter to allow the use of ordinary
		functions as Observers. If f is a function with the appropriate
		signature, ObserverFunc(f) is an Observer that calls f.

		This adapter is usually used in connection with the Timer type, and there are
		two general use cases:

		The most common one is to use a Gauge as the Observer for a Timer.
		See the "Gauge" Timer example.

		The more advanced use case is to create a function that dynamically decides
		which Observer to use for observing the duration. See the "Complex" Timer
		example.

		Methods (only one, which is exported)
			( T) Observe(value float64)
				Observe calls f(value). It implements Observer.

		Implements (at least one exported)
			 T : Observer

	 type ObserverVec (interface)
		ObserverVec is an interface implemented by `HistogramVec` and `SummaryVec`.

		Methods (total 8, all are exported)
			( T) Collect(chan<- Metric)
				Collect is called by the Prometheus registry when collecting
				metrics. The implementation sends each collected metric via the
				provided channel and returns once the last metric has been sent. The
				descriptor of each sent metric is one of those returned by Describe
				(unless the Collector is unchecked, see above). Returned metrics that
				share the same descriptor must differ in their variable label
				values.

				This method may be called concurrently and must therefore be
				implemented in a concurrency safe way. Blocking occurs at the expense
				of total performance of rendering all registered metrics. Ideally,
				Collector implementations support concurrent readers.

			( T) CurryWith(Labels) (ObserverVec, error)
			( T) Describe(chan<- *Desc)
				Describe sends the super-set of all possible descriptors of metrics
				collected by this Collector to the provided channel and returns once
				the last descriptor has been sent. The sent descriptors fulfill the
				consistency and uniqueness requirements described in the Desc
				documentation.

				It is valid if one and the same Collector sends duplicate
				descriptors. Those duplicates are simply ignored. However, two
				different Collectors must not send duplicate descriptors.

				Sending no descriptor at all marks the Collector as “unchecked”,
				i.e. no checks will be performed at registration time, and the
				Collector may yield any Metric it sees fit in its Collect method.

				This method idempotently sends the same descriptors throughout the
				lifetime of the Collector. It may be called concurrently and
				therefore must be implemented in a concurrency safe way.

				If a Collector encounters an error while executing this method, it
				must send an invalid descriptor (created with NewInvalidDesc) to
				signal the error to the registry.

			( T) GetMetricWith(Labels) (Observer, error)
			( T) GetMetricWithLabelValues(lvs ...string) (Observer, error)
			( T) MustCurryWith(Labels) ObserverVec
			( T) With(Labels) Observer
			( T) WithLabelValues(...string) Observer
		Implemented By (at least 2, both are exported)
			*HistogramVec
			*SummaryVec
		Implements (at least one exported)
			 T : Collector
		As Outputs Of (at least 6, all are exported)
			func (*HistogramVec).CurryWith(labels Labels) (ObserverVec, error)
			func (*HistogramVec).MustCurryWith(labels Labels) ObserverVec
			func ObserverVec.CurryWith(Labels) (ObserverVec, error)
			func ObserverVec.MustCurryWith(Labels) ObserverVec
			func (*SummaryVec).CurryWith(labels Labels) (ObserverVec, error)
			func (*SummaryVec).MustCurryWith(labels Labels) ObserverVec
		As Inputs Of (at least 5, all are exported)
			func github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerDuration(obs ObserverVec, next http.Handler) http.HandlerFunc
			func github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerRequestSize(obs ObserverVec, next http.Handler) http.HandlerFunc
			func github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerResponseSize(obs ObserverVec, next http.Handler) http.Handler
			func github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerTimeToWriteHeader(obs ObserverVec, next http.Handler) http.HandlerFunc
			func github.com/prometheus/client_golang/prometheus/promhttp.InstrumentRoundTripperDuration(obs ObserverVec, next http.RoundTripper) promhttp.RoundTripperFunc

	 type Opts (struct)
		Opts bundles the options for creating most Metric types. Each metric
		implementation XXX has its own XXXOpts type, but in most cases, it is just be
		an alias of this type (which might change when the requirement arises.)

		It is mandatory to set Name to a non-empty string. All other fields are
		optional and can safely be left at their zero value, although it is strongly
		encouraged to set a Help string.

		Fields (total 5, all are exported)
			ConstLabels Labels
				ConstLabels are used to attach fixed labels to this metric. Metrics
				with the same fully-qualified name must have the same label names in
				their ConstLabels.

				ConstLabels are only used rarely. In particular, do not use them to
				attach the same labels to all your metrics. Those use cases are
				better covered by target labels set by the scraping Prometheus
				server, or by one specific metric (e.g. a build_info or a
				machine_role metric). See also
				https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels,-not-static-scraped-labels

			Help string
				Help provides information about this metric.

				Metrics with the same fully-qualified name must have the same Help
				string.

			Name string
			Namespace string
				Namespace, Subsystem, and Name are components of the fully-qualified
				name of the Metric (created by joining these components with
				"_"). Only Name is mandatory, the others merely help structuring the
				name. Note that the fully-qualified name of the metric must be a
				valid Prometheus metric name.

			Subsystem string

	 type ProcessCollectorOpts (struct)
		ProcessCollectorOpts defines the behavior of a process metrics collector
		created with NewProcessCollector.

		Fields (total 3, all are exported)
			Namespace string
				If non-empty, each of the collected metrics is prefixed by the
				provided string and an underscore ("_").

			PidFn func() (int, error)
				PidFn returns the PID of the process the collector collects metrics
				for. It is called upon each collection. By default, the PID of the
				current process is used, as determined on construction time by
				calling os.Getpid().

			ReportErrors bool
				If true, any error encountered during collection is reported as an
				invalid metric (see NewInvalidMetric). Otherwise, errors are ignored
				and the collected metrics will be incomplete. (Possibly, no metrics
				will be collected at all.) While that's usually not desired, it is
				appropriate for the common "mix-in" of process metrics, where process
				metrics are nice to have, but failing to collect them should not
				disrupt the collection of the remaining metrics.

		As Inputs Of (at least one exported)
			func NewProcessCollector(opts ProcessCollectorOpts) Collector

	 type Registerer (interface)
		Registerer is the interface for the part of a registry in charge of
		registering and unregistering. Users of custom registries should use
		Registerer as type for registration purposes (rather than the Registry type
		directly). In that way, they are free to use custom Registerer implementation
		(e.g. for testing purposes).

		Methods (total 3, all are exported)
			( T) MustRegister(...Collector)
				MustRegister works like Register but registers any number of
				Collectors and panics upon the first registration that causes an
				error.

			( T) Register(Collector) error
				Register registers a new Collector to be included in metrics
				collection. It returns an error if the descriptors provided by the
				Collector are invalid or if they — in combination with descriptors of
				already registered Collectors — do not fulfill the consistency and
				uniqueness criteria described in the documentation of metric.Desc.

				If the provided Collector is equal to a Collector already registered
				(which includes the case of re-registering the same Collector), the
				returned error is an instance of AlreadyRegisteredError, which
				contains the previously registered Collector.

				A Collector whose Describe method does not yield any Desc is treated
				as unchecked. Registration will always succeed. No check for
				re-registering (see previous paragraph) is performed. Thus, the
				caller is responsible for not double-registering the same unchecked
				Collector, and for providing a Collector that will not cause
				inconsistent metrics on collection. (This would lead to scrape
				errors.)

			( T) Unregister(Collector) bool
				Unregister unregisters the Collector that equals the Collector passed
				in as an argument.  (Two Collectors are considered equal if their
				Describe method yields the same set of descriptors.) The function
				returns whether a Collector was unregistered. Note that an unchecked
				Collector cannot be unregistered (as its Describe method does not
				yield any descriptor).

				Note that even after unregistering, it will not be possible to
				register a new Collector that is inconsistent with the unregistered
				Collector, e.g. a Collector collecting metrics with the same name but
				a different help string. The rationale here is that the same registry
				instance must only collect consistent metrics throughout its
				lifetime.

		Implemented By (at least 2, in which 1 are exported)
			*Registry
			/* at least one unexported ... *//* at least one unexported: */
			*wrappingRegisterer
		As Outputs Of (at least 2, both are exported)
			func WrapRegistererWith(labels Labels, reg Registerer) Registerer
			func WrapRegistererWithPrefix(prefix string, reg Registerer) Registerer
		As Inputs Of (at least 3, all are exported)
			func WrapRegistererWith(labels Labels, reg Registerer) Registerer
			func WrapRegistererWithPrefix(prefix string, reg Registerer) Registerer
			func github.com/prometheus/client_golang/prometheus/promhttp.InstrumentMetricHandler(reg Registerer, handler http.Handler) http.Handler
		As Types Of (only one, which is exported)
			  var DefaultRegisterer

	 type Registry (struct)
		Registry registers Prometheus collectors, collects their metrics, and gathers
		them into MetricFamilies for exposition. It implements both Registerer and
		Gatherer. The zero value is not usable. Create instances with NewRegistry or
		NewPedanticRegistry.

		Fields (total 6, none are exported)
			/* 6 unexporteds ... *//* 6 unexporteds: */
			collectorsByID map[uint64]Collector
				// ID is a hash of the descIDs.

			descIDs map[uint64]struct{}
			dimHashesByName map[string]uint64
			mtx sync.RWMutex
			pedanticChecksEnabled bool
			uncheckedCollectors []Collector
		Methods (total 4, all are exported)
			(*T) Gather() ([]*dto.MetricFamily, error)
				Gather implements Gatherer.

			(*T) MustRegister(cs ...Collector)
				MustRegister implements Registerer.

			(*T) Register(c Collector) error
				Register implements Registerer.

			(*T) Unregister(c Collector) bool
				Unregister implements Registerer.

		Implements (at least 2, both are exported)
			*T : Gatherer
			*T : Registerer
		As Outputs Of (at least 2, both are exported)
			func NewPedanticRegistry() *Registry
			func NewRegistry() *Registry
		As Inputs Of (at least one unexported)
			/* at least one unexported ... *//* at least one unexported: */
			func contrib.go.opencensus.io/exporter/prometheus.newCollector(opts prometheus.Options, registrar *Registry) *prometheus.collector
		As Types Of (only one, which is unexported)
			/* one unexported ... *//* one unexported: */
			  var defaultRegistry *Registry

	 type Summary (interface)
		A Summary captures individual observations from an event or sample stream and
		summarizes them in a manner similar to traditional summary statistics: 1. sum
		of observations, 2. observation count, 3. rank estimations.

		A typical use-case is the observation of request latencies. By default, a
		Summary provides the median, the 90th and the 99th percentile of the latency
		as rank estimations. However, the default behavior will change in the
		upcoming v1.0.0 of the library. There will be no rank estimations at all by
		default. For a sane transition, it is recommended to set the desired rank
		estimations explicitly.

		Note that the rank estimations cannot be aggregated in a meaningful way with
		the Prometheus query language (i.e. you cannot average or add them). If you
		need aggregatable quantiles (e.g. you want the 99th percentile latency of all
		queries served across all instances of a service), consider the Histogram
		metric type. See the Prometheus documentation for more details.

		To create Summary instances, use NewSummary.

		Methods (total 5, all are exported)
			( T) Collect(chan<- Metric)
				Collect is called by the Prometheus registry when collecting
				metrics. The implementation sends each collected metric via the
				provided channel and returns once the last metric has been sent. The
				descriptor of each sent metric is one of those returned by Describe
				(unless the Collector is unchecked, see above). Returned metrics that
				share the same descriptor must differ in their variable label
				values.

				This method may be called concurrently and must therefore be
				implemented in a concurrency safe way. Blocking occurs at the expense
				of total performance of rendering all registered metrics. Ideally,
				Collector implementations support concurrent readers.

			( T) Desc() *Desc
				Desc returns the descriptor for the Metric. This method idempotently
				returns the same descriptor throughout the lifetime of the
				Metric. The returned descriptor is immutable by contract. A Metric
				unable to describe itself must return an invalid descriptor (created
				with NewInvalidDesc).

			( T) Describe(chan<- *Desc)
				Describe sends the super-set of all possible descriptors of metrics
				collected by this Collector to the provided channel and returns once
				the last descriptor has been sent. The sent descriptors fulfill the
				consistency and uniqueness requirements described in the Desc
				documentation.

				It is valid if one and the same Collector sends duplicate
				descriptors. Those duplicates are simply ignored. However, two
				different Collectors must not send duplicate descriptors.

				Sending no descriptor at all marks the Collector as “unchecked”,
				i.e. no checks will be performed at registration time, and the
				Collector may yield any Metric it sees fit in its Collect method.

				This method idempotently sends the same descriptors throughout the
				lifetime of the Collector. It may be called concurrently and
				therefore must be implemented in a concurrency safe way.

				If a Collector encounters an error while executing this method, it
				must send an invalid descriptor (created with NewInvalidDesc) to
				signal the error to the registry.

			( T) Observe(float64)
				Observe adds a single observation to the histogram.

			( T) Write(*dto.Metric) error
				Write encodes the Metric into a "Metric" Protocol Buffer data
				transmission object.

				Metric implementations must observe concurrency safety as reads of
				this metric may occur at any time, and any blocking occurs at the
				expense of total performance of rendering all registered
				metrics. Ideally, Metric implementations should support concurrent
				readers.

				While populating dto.Metric, it is the responsibility of the
				implementation to ensure validity of the Metric protobuf (like valid
				UTF-8 strings or syntactically valid metric and label names). It is
				recommended to sort labels lexicographically. Callers of Write should
				still make sure of sorting if they depend on it.

		Implemented By (at least 4, in which 1 are exported)
			 Histogram (interface)
			/* 3+ unexporteds ... *//* 3+ unexporteds: */
			*histogram
			*noObjectivesSummary
			*summary
		Implements (at least 7, all are exported)
			 T : Collector
			 T : CounterFunc
			 T : GaugeFunc
			 T : Histogram
			 T : Metric
			 T : Observer
			 T : UntypedFunc
		As Outputs Of (at least 2, in which 1 are exported)
			func NewSummary(opts SummaryOpts) Summary
			/* at least one unexported ... *//* at least one unexported: */
			func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary

	 type SummaryOpts (struct)
		SummaryOpts bundles the options for creating a Summary metric. It is
		mandatory to set Name to a non-empty string. While all other fields are
		optional and can safely be left at their zero value, it is recommended to set
		a help string and to explicitly set the Objectives field to the desired value
		as the default value will change in the upcoming v1.0.0 of the library.

		Fields (total 9, all are exported)
			AgeBuckets uint32
				AgeBuckets is the number of buckets used to exclude observations that
				are older than MaxAge from the summary. A higher number has a
				resource penalty, so only increase it if the higher resolution is
				really required. For very high observation rates, you might want to
				reduce the number of age buckets. With only one age bucket, you will
				effectively see a complete reset of the summary each time MaxAge has
				passed. The default value is DefAgeBuckets.

			BufCap uint32
				BufCap defines the default sample stream buffer size.  The default
				value of DefBufCap should suffice for most uses. If there is a need
				to increase the value, a multiple of 500 is recommended (because that
				is the internal buffer size of the underlying package
				"github.com/bmizerany/perks/quantile").

			ConstLabels Labels
				ConstLabels are used to attach fixed labels to this metric. Metrics
				with the same fully-qualified name must have the same label names in
				their ConstLabels.

				Due to the way a Summary is represented in the Prometheus text format
				and how it is handled by the Prometheus server internally, “quantile”
				is an illegal label name. Construction of a Summary or SummaryVec
				will panic if this label name is used in ConstLabels.

				ConstLabels are only used rarely. In particular, do not use them to
				attach the same labels to all your metrics. Those use cases are
				better covered by target labels set by the scraping Prometheus
				server, or by one specific metric (e.g. a build_info or a
				machine_role metric). See also
				https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels,-not-static-scraped-labels

			Help string
				Help provides information about this Summary.

				Metrics with the same fully-qualified name must have the same Help
				string.

			MaxAge time.Duration
				MaxAge defines the duration for which an observation stays relevant
				for the summary. Must be positive. The default value is DefMaxAge.

			Name string
			Namespace string
				Namespace, Subsystem, and Name are components of the fully-qualified
				name of the Summary (created by joining these components with
				"_"). Only Name is mandatory, the others merely help structuring the
				name. Note that the fully-qualified name of the Summary must be a
				valid Prometheus metric name.

			Objectives map[float64]float64
				Objectives defines the quantile rank estimates with their respective
				absolute error. If Objectives[q] = e, then the value reported for q
				will be the φ-quantile value for some φ between q-e and q+e.  The
				default value is an empty map, resulting in a summary without
				quantiles.

			Subsystem string
		As Inputs Of (at least 3, in which 2 are exported)
			func NewSummary(opts SummaryOpts) Summary
			func NewSummaryVec(opts SummaryOpts, labelNames []string) *SummaryVec
			/* at least one unexported ... *//* at least one unexported: */
			func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary

	 type SummaryVec (struct)
		SummaryVec is a Collector that bundles a set of Summaries that all share the
		same Desc, but have different values for their variable labels. This is used
		if you want to count the same thing partitioned by various dimensions
		(e.g. HTTP request latencies, partitioned by status code and method). Create
		instances with NewSummaryVec.

		Fields (total 9, none are exported)
			/* 9 unexporteds ... *//* 9 unexporteds: */
			metricVec *metricVec
			metricVec.curry []curriedLabelValue
			metricVec.hashAdd func(h uint64, s string) uint64
				hashAdd and hashAddByte can be replaced for testing collision handling.

			metricVec.hashAddByte func(h uint64, b byte) uint64
			metricVec.metricMap *metricMap
			metricVec.metricMap.desc *Desc
			metricVec.metricMap.metrics map[uint64][]metricWithLabelValues
			metricVec.metricMap.mtx sync.RWMutex
				// Protects metrics.

			metricVec.metricMap.newMetric func(labelValues ...string) Metric
		Methods (total 22, in which 11 are exported)
			( T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) CurryWith(labels Labels) (ObserverVec, error)
				CurryWith returns a vector curried with the provided labels, i.e. the
				returned vector has those labels pre-set for all labeled operations performed
				on it. The cardinality of the curried vector is reduced accordingly. The
				order of the remaining labels stays the same (just with the curried labels
				taken out of the sequence – which is relevant for the
				(GetMetric)WithLabelValues methods). It is possible to curry a curried
				vector, but only with labels not yet used for currying before.

				The metrics contained in the SummaryVec are shared between the curried and
				uncurried vectors. They are just accessed differently. Curried and uncurried
				vectors behave identically in terms of collection. Only one must be
				registered with a given registry (usually the uncurried version). The Reset
				method deletes all metrics, even if called on a curried vector.

			( T) Delete(labels Labels) bool
				Delete deletes the metric where the variable labels are the same as those
				passed in as labels. It returns true if a metric was deleted.

				It is not an error if the number and names of the Labels are inconsistent
				with those of the VariableLabels in Desc. However, such inconsistent Labels
				can never match an actual metric, so the method will always return false in
				that case.

				This method is used for the same purpose as DeleteLabelValues(...string). See
				there for pros and cons of the two methods.

			( T) DeleteLabelValues(lvs ...string) bool
				DeleteLabelValues removes the metric where the variable labels are the same
				as those passed in as labels (same order as the VariableLabels in Desc). It
				returns true if a metric was deleted.

				It is not an error if the number of label values is not the same as the
				number of VariableLabels in Desc. However, such inconsistent label count can
				never match an actual metric, so the method will always return false in that
				case.

				Note that for more than one label value, this method is prone to mistakes
				caused by an incorrect order of arguments. Consider Delete(Labels) as an
				alternative to avoid that type of mistake. For higher label numbers, the
				latter has a much more readable (albeit more verbose) syntax, but it comes
				with a performance overhead (for creating and processing the Labels map).
				See also the CounterVec example.

			( T) Describe(ch chan<- *Desc)
				Describe implements Collector. It will send exactly one Desc to the provided
				channel.

			(*T) GetMetricWith(labels Labels) (Observer, error)
				GetMetricWith returns the Summary for the given Labels map (the label names
				must match those of the VariableLabels in Desc). If that label map is
				accessed for the first time, a new Summary is created. Implications of
				creating a Summary without using it and keeping the Summary for later use are
				the same as for GetMetricWithLabelValues.

				An error is returned if the number and names of the Labels are inconsistent
				with those of the VariableLabels in Desc (minus any curried labels).

				This method is used for the same purpose as
				GetMetricWithLabelValues(...string). See there for pros and cons of the two
				methods.

			(*T) GetMetricWithLabelValues(lvs ...string) (Observer, error)
				GetMetricWithLabelValues returns the Summary for the given slice of label
				values (same order as the VariableLabels in Desc). If that combination of
				label values is accessed for the first time, a new Summary is created.

				It is possible to call this method without using the returned Summary to only
				create the new Summary but leave it at its starting value, a Summary without
				any observations.

				Keeping the Summary for later use is possible (and should be considered if
				performance is critical), but keep in mind that Reset, DeleteLabelValues and
				Delete can be used to delete the Summary from the SummaryVec. In that case,
				the Summary will still exist, but it will not be exported anymore, even if a
				Summary with the same label values is created later. See also the CounterVec
				example.

				An error is returned if the number of label values is not the same as the
				number of VariableLabels in Desc (minus any curried labels).

				Note that for more than one label value, this method is prone to mistakes
				caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
				an alternative to avoid that type of mistake. For higher label numbers, the
				latter has a much more readable (albeit more verbose) syntax, but it comes
				with a performance overhead (for creating and processing the Labels map).
				See also the GaugeVec example.

			(*T) MustCurryWith(labels Labels) ObserverVec
				MustCurryWith works as CurryWith but panics where CurryWith would have
				returned an error.

			( T) Reset()
				Reset deletes all metrics in this vector.

			(*T) With(labels Labels) Observer
				With works as GetMetricWith, but panics where GetMetricWithLabels would have
				returned an error. Not returning an error allows shortcuts like
				    myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Observe(42.21)

			(*T) WithLabelValues(lvs ...string) Observer
				WithLabelValues works as GetMetricWithLabelValues, but panics where
				GetMetricWithLabelValues would have returned an error. Not returning an
				error allows shortcuts like
				    myVec.WithLabelValues("404", "GET").Observe(42.21)

			/* 11 unexporteds ... *//* 11 unexporteds: */
			( T) curryWith(labels Labels) (*metricVec, error)
			( T) deleteByHashWithLabelValues(h uint64, lvs []string, curry []curriedLabelValue) bool
				deleteByHashWithLabelValues removes the metric from the hash bucket h. If
				there are multiple matches in the bucket, use lvs to select a metric and
				remove only that metric.

			( T) deleteByHashWithLabels(h uint64, labels Labels, curry []curriedLabelValue) bool
				deleteByHashWithLabels removes the metric from the hash bucket h. If there
				are multiple matches in the bucket, use lvs to select a metric and remove
				only that metric.

			( T) getMetricWith(labels Labels) (Metric, error)
			( T) getMetricWithHashAndLabelValues(h uint64, lvs []string, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabelValues gets a metric while handling possible
				collisions in the hash space. Must be called while holding the read mutex.

			( T) getMetricWithHashAndLabels(h uint64, labels Labels, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabels gets a metric while handling possible collisions in
				the hash space. Must be called while holding read mutex.

			( T) getMetricWithLabelValues(lvs ...string) (Metric, error)
			( T) getOrCreateMetricWithLabelValues(hash uint64, lvs []string, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			( T) getOrCreateMetricWithLabels(hash uint64, labels Labels, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			( T) hashLabelValues(vals []string) (uint64, error)
			( T) hashLabels(labels Labels) (uint64, error)
		Implements (at least 2, both are exported)
			 T : Collector
			*T : ObserverVec
		As Outputs Of (at least one exported)
			func NewSummaryVec(opts SummaryOpts, labelNames []string) *SummaryVec

	 type Timer (struct)
		Timer is a helper type to time functions. Use NewTimer to create new
		instances.

		Fields (total 2, neither is exported)
			/* 2 unexporteds ... *//* 2 unexporteds: */
			begin time.Time
			observer Observer
		Methods (only one, which is exported)
			(*T) ObserveDuration() time.Duration
				ObserveDuration records the duration passed since the Timer was created with
				NewTimer. It calls the Observe method of the Observer provided during
				construction with the duration in seconds as an argument. The observed
				duration is also returned. ObserveDuration is usually called with a defer
				statement.

				Note that this method is only guaranteed to never observe negative durations
				if used with Go1.9+.

		As Outputs Of (at least one exported)
			func NewTimer(o Observer) *Timer

	 type UntypedFunc (interface)
		UntypedFunc works like GaugeFunc but the collected metric is of type
		"Untyped". UntypedFunc is useful to mirror an external metric of unknown
		type.

		To create UntypedFunc instances, use NewUntypedFunc.

		Methods (total 4, all are exported)
			( T) Collect(chan<- Metric)
				Collect is called by the Prometheus registry when collecting
				metrics. The implementation sends each collected metric via the
				provided channel and returns once the last metric has been sent. The
				descriptor of each sent metric is one of those returned by Describe
				(unless the Collector is unchecked, see above). Returned metrics that
				share the same descriptor must differ in their variable label
				values.

				This method may be called concurrently and must therefore be
				implemented in a concurrency safe way. Blocking occurs at the expense
				of total performance of rendering all registered metrics. Ideally,
				Collector implementations support concurrent readers.

			( T) Desc() *Desc
				Desc returns the descriptor for the Metric. This method idempotently
				returns the same descriptor throughout the lifetime of the
				Metric. The returned descriptor is immutable by contract. A Metric
				unable to describe itself must return an invalid descriptor (created
				with NewInvalidDesc).

			( T) Describe(chan<- *Desc)
				Describe sends the super-set of all possible descriptors of metrics
				collected by this Collector to the provided channel and returns once
				the last descriptor has been sent. The sent descriptors fulfill the
				consistency and uniqueness requirements described in the Desc
				documentation.

				It is valid if one and the same Collector sends duplicate
				descriptors. Those duplicates are simply ignored. However, two
				different Collectors must not send duplicate descriptors.

				Sending no descriptor at all marks the Collector as “unchecked”,
				i.e. no checks will be performed at registration time, and the
				Collector may yield any Metric it sees fit in its Collect method.

				This method idempotently sends the same descriptors throughout the
				lifetime of the Collector. It may be called concurrently and
				therefore must be implemented in a concurrency safe way.

				If a Collector encounters an error while executing this method, it
				must send an invalid descriptor (created with NewInvalidDesc) to
				signal the error to the registry.

			( T) Write(*dto.Metric) error
				Write encodes the Metric into a "Metric" Protocol Buffer data
				transmission object.

				Metric implementations must observe concurrency safety as reads of
				this metric may occur at any time, and any blocking occurs at the
				expense of total performance of rendering all registered
				metrics. Ideally, Metric implementations should support concurrent
				readers.

				While populating dto.Metric, it is the responsibility of the
				implementation to ensure validity of the Metric protobuf (like valid
				UTF-8 strings or syntactically valid metric and label names). It is
				recommended to sort labels lexicographically. Callers of Write should
				still make sure of sorting if they depend on it.

		Implemented By (at least 12, in which 6 are exported)
			 Counter (interface)
			 CounterFunc (interface)
			 Gauge (interface)
			 GaugeFunc (interface)
			 Histogram (interface)
			 Summary (interface)
			/* 6+ unexporteds ... *//* 6+ unexporteds: */
			*counter
			*gauge
			*histogram
			*noObjectivesSummary
			*summary
			*valueFunc
		Implements (at least 4, all are exported)
			 T : Collector
			 T : CounterFunc
			 T : GaugeFunc
			 T : Metric
		As Outputs Of (at least one exported)
			func NewUntypedFunc(opts UntypedOpts, function func() float64) UntypedFunc

	 type UntypedOpts Opts (struct)
		UntypedOpts is an alias for Opts. See there for doc comments.

		Fields (total 5, all are exported)
			ConstLabels Labels
				ConstLabels are used to attach fixed labels to this metric. Metrics
				with the same fully-qualified name must have the same label names in
				their ConstLabels.

				ConstLabels are only used rarely. In particular, do not use them to
				attach the same labels to all your metrics. Those use cases are
				better covered by target labels set by the scraping Prometheus
				server, or by one specific metric (e.g. a build_info or a
				machine_role metric). See also
				https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels,-not-static-scraped-labels

			Help string
				Help provides information about this metric.

				Metrics with the same fully-qualified name must have the same Help
				string.

			Name string
			Namespace string
				Namespace, Subsystem, and Name are components of the fully-qualified
				name of the Metric (created by joining these components with
				"_"). Only Name is mandatory, the others merely help structuring the
				name. Note that the fully-qualified name of the metric must be a
				valid Prometheus metric name.

			Subsystem string
		As Inputs Of (at least one exported)
			func NewUntypedFunc(opts UntypedOpts, function func() float64) UntypedFunc

	 type ValueType int (basic type)
		ValueType is an enumeration of metric types that represent a simple value.

		As Inputs Of (at least 4, in which 2 are exported)
			func MustNewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) Metric
			func NewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) (Metric, error)
			/* 2+ unexporteds ... *//* 2+ unexporteds: */
			func newValueFunc(desc *Desc, valueType ValueType, function func() float64) *valueFunc
			func populateMetric(t ValueType, v float64, labelPairs []*dto.LabelPair, m *dto.Metric) error
		As Types Of (total 3, all are exported)
			const CounterValue
			const GaugeValue
			const UntypedValue

	/* 28 unexporteds ... *//* 28 unexporteds: */
	 type buckSort ([]T)

		Methods (total 3, all are exported)
			( T) Len() int
			( T) Less(i, j int) bool
			( T) Swap(i, j int)
		Implements (at least 2, in which 1 are exported)
			 T : sort.Interface
			/* at least one unexported ... *//* at least one unexported: */
			 T : github.com/aws/aws-sdk-go/aws/corehandlers.lener

	 type constHistogram (struct)

		Fields (total 5, none are exported)
			/* 5 unexporteds ... *//* 5 unexporteds: */
			buckets map[float64]uint64
			count uint64
			desc *Desc
			labelPairs []*dto.LabelPair
			sum float64
		Methods (total 2, both are exported)
			(*T) Desc() *Desc
			(*T) Write(out *dto.Metric) error
		Implements (at least one exported)
			*T : Metric

	 type constMetric (struct)

		Fields (total 4, none are exported)
			/* 4 unexporteds ... *//* 4 unexporteds: */
			desc *Desc
			labelPairs []*dto.LabelPair
			val float64
			valType ValueType
		Methods (total 2, both are exported)
			(*T) Desc() *Desc
			(*T) Write(out *dto.Metric) error
		Implements (at least one exported)
			*T : Metric

	 type constSummary (struct)

		Fields (total 5, none are exported)
			/* 5 unexporteds ... *//* 5 unexporteds: */
			count uint64
			desc *Desc
			labelPairs []*dto.LabelPair
			quantiles map[float64]float64
			sum float64
		Methods (total 2, both are exported)
			(*T) Desc() *Desc
			(*T) Write(out *dto.Metric) error
		Implements (at least one exported)
			*T : Metric

	 type counter (struct)

		Fields (total 6, none are exported)
			/* 6 unexporteds ... *//* 6 unexporteds: */
			desc *Desc
			labelPairs []*dto.LabelPair
			selfCollector selfCollector
			selfCollector.self Metric
			valBits uint64
				valBits contains the bits of the represented float64 value, while
				valInt stores values that are exact integers. Both have to go first
				in the struct to guarantee alignment for atomic operations.
				http://golang.org/pkg/sync/atomic/#pkg-note-BUG

			valInt uint64
		Methods (total 7, in which 6 are exported)
			(*T) Add(v float64)
			(*T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) Desc() *Desc
			(*T) Describe(ch chan<- *Desc)
				Describe implements Collector.

			(*T) Inc()
			(*T) Write(out *dto.Metric) error
			/* one unexported ... *//* one unexported: */
			(*T) init(self Metric)
				init provides the selfCollector with a reference to the metric it is supposed
				to collect. It is usually called within the factory function to create a
				metric. See example.

		Implements (at least 6, all are exported)
			*T : Collector
			*T : Counter
			*T : CounterFunc
			*T : GaugeFunc
			*T : Metric
			*T : UntypedFunc

	 type curriedLabelValue (struct)
		curriedLabelValue sets the curried value for a label at the given index.

		Fields (total 2, neither is exported)
			/* 2 unexporteds ... *//* 2 unexporteds: */
			index int
			value string
		As Inputs Of (at least 6, none are exported)
			/* 6+ unexporteds ... *//* 6+ unexporteds: */
			func extractLabelValues(desc *Desc, labels Labels, curry []curriedLabelValue) []string
			func findMetricWithLabels(desc *Desc, metrics []metricWithLabelValues, labels Labels, curry []curriedLabelValue) int
			func findMetricWithLabelValues(metrics []metricWithLabelValues, lvs []string, curry []curriedLabelValue) int
			func inlineLabelValues(lvs []string, curry []curriedLabelValue) []string
			func matchLabels(desc *Desc, values []string, labels Labels, curry []curriedLabelValue) bool
			func matchLabelValues(values []string, lvs []string, curry []curriedLabelValue) bool

	 type expvarCollector (struct)

		Fields (only one, which is unexported)
			/* one unexported ... *//* one unexported: */
			exports map[string]*Desc
		Methods (total 2, both are exported)
			(*T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) Describe(ch chan<- *Desc)
				Describe implements Collector.

		Implements (at least one exported)
			*T : Collector

	 type gauge (struct)

		Fields (total 5, none are exported)
			/* 5 unexporteds ... *//* 5 unexporteds: */
			desc *Desc
			labelPairs []*dto.LabelPair
			selfCollector selfCollector
			selfCollector.self Metric
			valBits uint64
				valBits contains the bits of the represented float64 value. It has
				to go first in the struct to guarantee alignment for atomic
				operations.  http://golang.org/pkg/sync/atomic/#pkg-note-BUG

		Methods (total 11, in which 10 are exported)
			(*T) Add(val float64)
			(*T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) Dec()
			(*T) Desc() *Desc
			(*T) Describe(ch chan<- *Desc)
				Describe implements Collector.

			(*T) Inc()
			(*T) Set(val float64)
			(*T) SetToCurrentTime()
			(*T) Sub(val float64)
			(*T) Write(out *dto.Metric) error
			/* one unexported ... *//* one unexported: */
			(*T) init(self Metric)
				init provides the selfCollector with a reference to the metric it is supposed
				to collect. It is usually called within the factory function to create a
				metric. See example.

		Implements (at least 7, all are exported)
			*T : Collector
			*T : Counter
			*T : CounterFunc
			*T : Gauge
			*T : GaugeFunc
			*T : Metric
			*T : UntypedFunc

	 type goCollector (struct)

		Fields (total 11, none are exported)
			/* 11 unexporteds ... *//* 11 unexporteds: */
			gcDesc *Desc
			goInfoDesc *Desc
			goroutinesDesc *Desc
			msLast *runtime.MemStats
				ms... are memstats related.
				// Previously collected memstats.

			msLastTimestamp time.Time
			msMaxAge time.Duration
				// Maximum allowed age of old memstats.

			msMaxWait time.Duration
				// Wait time for fresh memstats.

			msMetrics memStatsMetrics
			msMtx sync.Mutex
				// Protects msLast and msLastTimestamp.

			msRead func(*runtime.MemStats)
				// For mocking in tests.

			threadsDesc *Desc
		Methods (total 3, in which 2 are exported)
			(*T) Collect(ch chan<- Metric)
				Collect returns the current state of all metrics of the collector.

			(*T) Describe(ch chan<- *Desc)
				Describe returns all descriptions of the collector.

			/* one unexported ... *//* one unexported: */
			(*T) msCollect(ch chan<- Metric, ms *runtime.MemStats)
		Implements (at least one exported)
			*T : Collector

	 type histogram (struct)

		Fields (total 8, none are exported)
			/* 8 unexporteds ... *//* 8 unexporteds: */
			countAndHotIdx uint64
				countAndHotIdx enables lock-free writes with use of atomic updates.
				The most significant bit is the hot index [0 or 1] of the count field
				below. Observe calls update the hot one. All remaining bits count the
				number of Observe calls. Observe starts by incrementing this counter,
				and finish by incrementing the count field in the respective
				histogramCounts, as a marker for completion.

				Calls of the Write method (which are non-mutating reads from the
				perspective of the histogram) swap the hot–cold under the writeMtx
				lock. A cooldown is awaited (while locked) by comparing the number of
				observations with the initiation count. Once they match, then the
				last observation on the now cool one has completed. All cool fields must
				be merged into the new hot before releasing writeMtx.

				Fields with atomic access first! See alignment constraint:
				http://golang.org/pkg/sync/atomic/#pkg-note-BUG

			counts [2]*histogramCounts
				Two counts, one is "hot" for lock-free observations, the other is
				"cold" for writing out a dto.Metric. It has to be an array of
				pointers to guarantee 64bit alignment of the histogramCounts, see
				http://golang.org/pkg/sync/atomic/#pkg-note-BUG.

			desc *Desc
			labelPairs []*dto.LabelPair
			selfCollector selfCollector
			selfCollector.self Metric
			upperBounds []float64
			writeMtx sync.Mutex
				// Only used in the Write method.

		Methods (total 6, in which 5 are exported)
			(*T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) Desc() *Desc
			(*T) Describe(ch chan<- *Desc)
				Describe implements Collector.

			(*T) Observe(v float64)
			(*T) Write(out *dto.Metric) error
			/* one unexported ... *//* one unexported: */
			(*T) init(self Metric)
				init provides the selfCollector with a reference to the metric it is supposed
				to collect. It is usually called within the factory function to create a
				metric. See example.

		Implements (at least 8, all are exported)
			*T : Collector
			*T : CounterFunc
			*T : GaugeFunc
			*T : Histogram
			*T : Metric
			*T : Observer
			*T : Summary
			*T : UntypedFunc

	 type histogramCounts (struct)

		Fields (total 3, none are exported)
			/* 3 unexporteds ... *//* 3 unexporteds: */
			buckets []uint64
			count uint64
			sumBits uint64
				sumBits contains the bits of the float64 representing the sum of all
				observations. sumBits and count have to go first in the struct to
				guarantee alignment for atomic operations.
				http://golang.org/pkg/sync/atomic/#pkg-note-BUG


	 type invalidMetric (struct)

		Fields (total 2, neither is exported)
			/* 2 unexporteds ... *//* 2 unexporteds: */
			desc *Desc
			err error
		Methods (total 2, both are exported)
			(*T) Desc() *Desc
			(*T) Write(*dto.Metric) error
		Implements (at least one exported)
			*T : Metric

	 type labelPairSorter ([]T)
		labelPairSorter implements sort.Interface. It is used to sort a slice of
		dto.LabelPair pointers.

		Methods (total 3, all are exported)
			( T) Len() int
			( T) Less(i, j int) bool
			( T) Swap(i, j int)
		Implements (at least 2, in which 1 are exported)
			 T : sort.Interface
			/* at least one unexported ... *//* at least one unexported: */
			 T : github.com/aws/aws-sdk-go/aws/corehandlers.lener

	 type memStatsMetrics ([]T)
		memStatsMetrics provide description, value, and value type for memstat metrics.


	 type metricMap (struct)
		metricMap is a helper for metricVec and shared between differently curried
		metricVecs.

		Fields (total 4, none are exported)
			/* 4 unexporteds ... *//* 4 unexporteds: */
			desc *Desc
			metrics map[uint64][]metricWithLabelValues
			mtx sync.RWMutex
				// Protects metrics.

			newMetric func(labelValues ...string) Metric
		Methods (total 9, in which 3 are exported)
			(*T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) Describe(ch chan<- *Desc)
				Describe implements Collector. It will send exactly one Desc to the provided
				channel.

			(*T) Reset()
				Reset deletes all metrics in this vector.

			/* 6 unexporteds ... *//* 6 unexporteds: */
			(*T) deleteByHashWithLabelValues(h uint64, lvs []string, curry []curriedLabelValue) bool
				deleteByHashWithLabelValues removes the metric from the hash bucket h. If
				there are multiple matches in the bucket, use lvs to select a metric and
				remove only that metric.

			(*T) deleteByHashWithLabels(h uint64, labels Labels, curry []curriedLabelValue) bool
				deleteByHashWithLabels removes the metric from the hash bucket h. If there
				are multiple matches in the bucket, use lvs to select a metric and remove
				only that metric.

			(*T) getMetricWithHashAndLabelValues(h uint64, lvs []string, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabelValues gets a metric while handling possible
				collisions in the hash space. Must be called while holding the read mutex.

			(*T) getMetricWithHashAndLabels(h uint64, labels Labels, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabels gets a metric while handling possible collisions in
				the hash space. Must be called while holding read mutex.

			(*T) getOrCreateMetricWithLabelValues(hash uint64, lvs []string, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			(*T) getOrCreateMetricWithLabels(hash uint64, labels Labels, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

		Implements (at least one exported)
			*T : Collector

	 type metricVec (struct)
		metricVec is a Collector to bundle metrics of the same name that differ in
		their label values. metricVec is not used directly (and therefore
		unexported). It is used as a building block for implementations of vectors of
		a given metric type, like GaugeVec, CounterVec, SummaryVec, and HistogramVec.
		It also handles label currying.

		Fields (total 8, none are exported)
			/* 8 unexporteds ... *//* 8 unexporteds: */
			curry []curriedLabelValue
			hashAdd func(h uint64, s string) uint64
				hashAdd and hashAddByte can be replaced for testing collision handling.

			hashAddByte func(h uint64, b byte) uint64
			metricMap *metricMap
			metricMap.desc *Desc
			metricMap.metrics map[uint64][]metricWithLabelValues
			metricMap.mtx sync.RWMutex
				// Protects metrics.

			metricMap.newMetric func(labelValues ...string) Metric
		Methods (total 16, in which 5 are exported)
			( T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) Delete(labels Labels) bool
				Delete deletes the metric where the variable labels are the same as those
				passed in as labels. It returns true if a metric was deleted.

				It is not an error if the number and names of the Labels are inconsistent
				with those of the VariableLabels in Desc. However, such inconsistent Labels
				can never match an actual metric, so the method will always return false in
				that case.

				This method is used for the same purpose as DeleteLabelValues(...string). See
				there for pros and cons of the two methods.

			(*T) DeleteLabelValues(lvs ...string) bool
				DeleteLabelValues removes the metric where the variable labels are the same
				as those passed in as labels (same order as the VariableLabels in Desc). It
				returns true if a metric was deleted.

				It is not an error if the number of label values is not the same as the
				number of VariableLabels in Desc. However, such inconsistent label count can
				never match an actual metric, so the method will always return false in that
				case.

				Note that for more than one label value, this method is prone to mistakes
				caused by an incorrect order of arguments. Consider Delete(Labels) as an
				alternative to avoid that type of mistake. For higher label numbers, the
				latter has a much more readable (albeit more verbose) syntax, but it comes
				with a performance overhead (for creating and processing the Labels map).
				See also the CounterVec example.

			( T) Describe(ch chan<- *Desc)
				Describe implements Collector. It will send exactly one Desc to the provided
				channel.

			( T) Reset()
				Reset deletes all metrics in this vector.

			/* 11 unexporteds ... *//* 11 unexporteds: */
			(*T) curryWith(labels Labels) (*metricVec, error)
			( T) deleteByHashWithLabelValues(h uint64, lvs []string, curry []curriedLabelValue) bool
				deleteByHashWithLabelValues removes the metric from the hash bucket h. If
				there are multiple matches in the bucket, use lvs to select a metric and
				remove only that metric.

			( T) deleteByHashWithLabels(h uint64, labels Labels, curry []curriedLabelValue) bool
				deleteByHashWithLabels removes the metric from the hash bucket h. If there
				are multiple matches in the bucket, use lvs to select a metric and remove
				only that metric.

			(*T) getMetricWith(labels Labels) (Metric, error)
			( T) getMetricWithHashAndLabelValues(h uint64, lvs []string, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabelValues gets a metric while handling possible
				collisions in the hash space. Must be called while holding the read mutex.

			( T) getMetricWithHashAndLabels(h uint64, labels Labels, curry []curriedLabelValue) (Metric, bool)
				getMetricWithHashAndLabels gets a metric while handling possible collisions in
				the hash space. Must be called while holding read mutex.

			(*T) getMetricWithLabelValues(lvs ...string) (Metric, error)
			( T) getOrCreateMetricWithLabelValues(hash uint64, lvs []string, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			( T) getOrCreateMetricWithLabels(hash uint64, labels Labels, curry []curriedLabelValue) Metric
				getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
				or creates it and returns the new one.

				This function holds the mutex.

			(*T) hashLabelValues(vals []string) (uint64, error)
			(*T) hashLabels(labels Labels) (uint64, error)
		Implements (at least one exported)
			 T : Collector
		As Outputs Of (at least one unexported)
			/* at least one unexported ... *//* at least one unexported: */
			func newMetricVec(desc *Desc, newMetric func(lvs ...string) Metric) *metricVec

	 type metricWithLabelValues (struct)
		metricWithLabelValues provides the metric and its label values for
		disambiguation on hash collision.

		Fields (total 2, neither is exported)
			/* 2 unexporteds ... *//* 2 unexporteds: */
			metric Metric
			values []string
		As Inputs Of (at least 2, neither is exported)
			/* 2+ unexporteds ... *//* 2+ unexporteds: */
			func findMetricWithLabels(desc *Desc, metrics []metricWithLabelValues, labels Labels, curry []curriedLabelValue) int
			func findMetricWithLabelValues(metrics []metricWithLabelValues, lvs []string, curry []curriedLabelValue) int

	 type noObjectivesSummary (struct)

		Fields (total 7, none are exported)
			/* 7 unexporteds ... *//* 7 unexporteds: */
			countAndHotIdx uint64
				Fields with atomic access first! See alignment constraint:
				http://golang.org/pkg/sync/atomic/#pkg-note-BUG

			counts [2]*summaryCounts
				Two counts, one is "hot" for lock-free observations, the other is
				"cold" for writing out a dto.Metric. It has to be an array of
				pointers to guarantee 64bit alignment of the histogramCounts, see
				http://golang.org/pkg/sync/atomic/#pkg-note-BUG.

			desc *Desc
			labelPairs []*dto.LabelPair
			selfCollector selfCollector
			selfCollector.self Metric
			writeMtx sync.Mutex
				// Only used in the Write method.

		Methods (total 6, in which 5 are exported)
			(*T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) Desc() *Desc
			(*T) Describe(ch chan<- *Desc)
				Describe implements Collector.

			(*T) Observe(v float64)
			(*T) Write(out *dto.Metric) error
			/* one unexported ... *//* one unexported: */
			(*T) init(self Metric)
				init provides the selfCollector with a reference to the metric it is supposed
				to collect. It is usually called within the factory function to create a
				metric. See example.

		Implements (at least 8, all are exported)
			*T : Collector
			*T : CounterFunc
			*T : GaugeFunc
			*T : Histogram
			*T : Metric
			*T : Observer
			*T : Summary
			*T : UntypedFunc

	 type processCollector (struct)

		Fields (total 10, none are exported)
			/* 10 unexporteds ... *//* 10 unexporteds: */
			collectFn func(chan<- Metric)
			cpuTotal *Desc
			maxFDs *Desc
			maxVsize *Desc
			openFDs *Desc
			pidFn func() (int, error)
			reportErrors bool
			rss *Desc
			startTime *Desc
			vsize *Desc
		Methods (total 4, in which 2 are exported)
			(*T) Collect(ch chan<- Metric)
				Collect returns the current state of all metrics of the collector.

			(*T) Describe(ch chan<- *Desc)
				Describe returns all descriptions of the collector.

			/* 2 unexporteds ... *//* 2 unexporteds: */
			(*T) processCollect(ch chan<- Metric)
			(*T) reportError(ch chan<- Metric, desc *Desc, err error)
		Implements (at least one exported)
			*T : Collector

	 type quantSort ([]T)

		Methods (total 3, all are exported)
			( T) Len() int
			( T) Less(i, j int) bool
			( T) Swap(i, j int)
		Implements (at least 2, in which 1 are exported)
			 T : sort.Interface
			/* at least one unexported ... *//* at least one unexported: */
			 T : github.com/aws/aws-sdk-go/aws/corehandlers.lener

	 type selfCollector (struct)
		selfCollector implements Collector for a single Metric so that the Metric
		collects itself. Add it as an anonymous field to a struct that implements
		Metric, and call init with the Metric itself as an argument.

		Fields (only one, which is unexported)
			/* one unexported ... *//* one unexported: */
			self Metric
		Methods (total 3, in which 2 are exported)
			(*T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) Describe(ch chan<- *Desc)
				Describe implements Collector.

			/* one unexported ... *//* one unexported: */
			(*T) init(self Metric)
				init provides the selfCollector with a reference to the metric it is supposed
				to collect. It is usually called within the factory function to create a
				metric. See example.

		Implements (at least one exported)
			*T : Collector

	 type summary (struct)

		Fields (total 18, none are exported)
			/* 18 unexporteds ... *//* 18 unexporteds: */
			bufMtx sync.Mutex
				// Protects hotBuf and hotBufExpTime.

			cnt uint64
			coldBuf []float64
			desc *Desc
			headStream *quantile.Stream
			headStreamExpTime time.Time
			headStreamIdx int
			hotBuf []float64
			hotBufExpTime time.Time
			labelPairs []*dto.LabelPair
			mtx sync.Mutex
				// Protects every other moving part.

			objectives map[float64]float64
			selfCollector selfCollector
			selfCollector.self Metric
			sortedObjectives []float64
			streamDuration time.Duration
			streams []*quantile.Stream
			sum float64
		Methods (total 11, in which 5 are exported)
			(*T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) Desc() *Desc
			(*T) Describe(ch chan<- *Desc)
				Describe implements Collector.

			(*T) Observe(v float64)
			(*T) Write(out *dto.Metric) error
			/* 6 unexporteds ... *//* 6 unexporteds: */
			(*T) asyncFlush(now time.Time)
				asyncFlush needs bufMtx locked.

			(*T) flushColdBuf()
				flushColdBuf needs mtx locked.

			(*T) init(self Metric)
				init provides the selfCollector with a reference to the metric it is supposed
				to collect. It is usually called within the factory function to create a
				metric. See example.

			(*T) maybeRotateStreams()
				rotateStreams needs mtx AND bufMtx locked.

			(*T) newStream() *quantile.Stream
			(*T) swapBufs(now time.Time)
				swapBufs needs mtx AND bufMtx locked, coldBuf must be empty.

		Implements (at least 8, all are exported)
			*T : Collector
			*T : CounterFunc
			*T : GaugeFunc
			*T : Histogram
			*T : Metric
			*T : Observer
			*T : Summary
			*T : UntypedFunc

	 type summaryCounts (struct)

		Fields (total 2, neither is exported)
			/* 2 unexporteds ... *//* 2 unexporteds: */
			count uint64
			sumBits uint64
				sumBits contains the bits of the float64 representing the sum of all
				observations. sumBits and count have to go first in the struct to
				guarantee alignment for atomic operations.
				http://golang.org/pkg/sync/atomic/#pkg-note-BUG


	 type timestampedMetric (struct)

		Fields (total 2, in which 1 are exported)
			Metric Metric
			/* one unexported ... *//* one unexported: */
			t time.Time
		Methods (total 2, both are exported)
			( T) Desc() *Desc
				Desc returns the descriptor for the Metric. This method idempotently
				returns the same descriptor throughout the lifetime of the
				Metric. The returned descriptor is immutable by contract. A Metric
				unable to describe itself must return an invalid descriptor (created
				with NewInvalidDesc).

			( T) Write(pb *dto.Metric) error
		Implements (at least one exported)
			 T : Metric

	 type valueFunc (struct)
		valueFunc is a generic metric for simple values retrieved on collect time
		from a function. It implements Metric and Collector. Its effective type is
		determined by ValueType. This is a low-level building block used by the
		library to back the implementations of CounterFunc, GaugeFunc, and
		UntypedFunc.

		Fields (total 6, none are exported)
			/* 6 unexporteds ... *//* 6 unexporteds: */
			desc *Desc
			function func() float64
			labelPairs []*dto.LabelPair
			selfCollector selfCollector
			selfCollector.self Metric
			valType ValueType
		Methods (total 5, in which 4 are exported)
			(*T) Collect(ch chan<- Metric)
				Collect implements Collector.

			(*T) Desc() *Desc
			(*T) Describe(ch chan<- *Desc)
				Describe implements Collector.

			(*T) Write(out *dto.Metric) error
			/* one unexported ... *//* one unexported: */
			(*T) init(self Metric)
				init provides the selfCollector with a reference to the metric it is supposed
				to collect. It is usually called within the factory function to create a
				metric. See example.

		Implements (at least 5, all are exported)
			*T : Collector
			*T : CounterFunc
			*T : GaugeFunc
			*T : Metric
			*T : UntypedFunc
		As Outputs Of (at least one unexported)
			/* at least one unexported ... *//* at least one unexported: */
			func newValueFunc(desc *Desc, valueType ValueType, function func() float64) *valueFunc

	 type wrappingCollector (struct)

		Fields (total 3, none are exported)
			/* 3 unexporteds ... *//* 3 unexporteds: */
			labels Labels
			prefix string
			wrappedCollector Collector
		Methods (total 3, in which 2 are exported)
			(*T) Collect(ch chan<- Metric)
			(*T) Describe(ch chan<- *Desc)
			/* one unexported ... *//* one unexported: */
			(*T) unwrapRecursively() Collector
		Implements (at least one exported)
			*T : Collector

	 type wrappingMetric (struct)

		Fields (total 3, none are exported)
			/* 3 unexporteds ... *//* 3 unexporteds: */
			labels Labels
			prefix string
			wrappedMetric Metric
		Methods (total 2, both are exported)
			(*T) Desc() *Desc
			(*T) Write(out *dto.Metric) error
		Implements (at least one exported)
			*T : Metric

	 type wrappingRegisterer (struct)

		Fields (total 3, none are exported)
			/* 3 unexporteds ... *//* 3 unexporteds: */
			labels Labels
			prefix string
			wrappedRegisterer Registerer
		Methods (total 3, all are exported)
			(*T) MustRegister(cs ...Collector)
			(*T) Register(c Collector) error
			(*T) Unregister(c Collector) bool
		Implements (at least one exported)
			*T : Registerer


Package-Level Functions (total 66, in which 38 are exported)

	 func BuildFQName(namespace, subsystem, name string) string
		BuildFQName joins the given three name components by "_". Empty name
		components are ignored. If the name parameter itself is empty, an empty
		string is returned, no matter what. Metric implementations included in this
		library use this function internally to generate the fully-qualified metric
		name from the name component in their Opts. Users of the library will only
		need this function if they implement their own Metric or instantiate a Desc
		(with NewDesc) directly.

	 func DescribeByCollect(c Collector, descs chan<- *Desc)
		DescribeByCollect is a helper to implement the Describe method of a custom
		Collector. It collects the metrics from the provided Collector and sends
		their descriptors to the provided channel.

		If a Collector collects the same metrics throughout its lifetime, its
		Describe method can simply be implemented as:

		  func (c customCollector) Describe(ch chan<- *Desc) {
		  	DescribeByCollect(c, ch)
		  }

		However, this will not work if the metrics collected change dynamically over
		the lifetime of the Collector in a way that their combined set of descriptors
		changes as well. The shortcut implementation will then violate the contract
		of the Describe method. If a Collector sometimes collects no metrics at all
		(for example vectors like CounterVec, GaugeVec, etc., which only collect
		metrics after a metric with a fully specified label set has been accessed),
		it might even get registered as an unchecked Collector (cf. the Register
		method of the Registerer interface). Hence, only use this shortcut
		implementation of Describe if you are certain to fulfill the contract.

		The Collector example demonstrates a use of DescribeByCollect.

	 func ExponentialBuckets(start, factor float64, count int) []float64
		ExponentialBuckets creates 'count' buckets, where the lowest bucket has an
		upper bound of 'start' and each following bucket's upper bound is 'factor'
		times the previous bucket's upper bound. The final +Inf bucket is not counted
		and not included in the returned slice. The returned slice is meant to be
		used for the Buckets field of HistogramOpts.

		The function panics if 'count' is 0 or negative, if 'start' is 0 or negative,
		or if 'factor' is less than or equal 1.

	 func LinearBuckets(start, width float64, count int) []float64
		LinearBuckets creates 'count' buckets, each 'width' wide, where the lowest
		bucket has an upper bound of 'start'. The final +Inf bucket is not counted
		and not included in the returned slice. The returned slice is meant to be
		used for the Buckets field of HistogramOpts.

		The function panics if 'count' is zero or negative.

	 func MustNewConstHistogram(desc *Desc, count uint64, sum float64, buckets map[float64]uint64, labelValues ...string) Metric
		MustNewConstHistogram is a version of NewConstHistogram that panics where
		NewConstMetric would have returned an error.

	 func MustNewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) Metric
		MustNewConstMetric is a version of NewConstMetric that panics where
		NewConstMetric would have returned an error.

	 func MustNewConstSummary(desc *Desc, count uint64, sum float64, quantiles map[float64]float64, labelValues ...string) Metric
		MustNewConstSummary is a version of NewConstSummary that panics where
		NewConstMetric would have returned an error.

	 func MustRegister(cs ...Collector)
		MustRegister registers the provided Collectors with the DefaultRegisterer and
		panics if any error occurs.

		MustRegister is a shortcut for DefaultRegisterer.MustRegister(cs...). See
		there for more details.

	 func NewBuildInfoCollector() Collector
		NewBuildInfoCollector returns a collector collecting a single metric
		"go_build_info" with the constant value 1 and three labels "path", "version",
		and "checksum". Their label values contain the main module path, version, and
		checksum, respectively. The labels will only have meaningful values if the
		binary is built with Go module support and from source code retrieved from
		the source repository (rather than the local file system). This is usually
		accomplished by building from outside of GOPATH, specifying the full address
		of the main package, e.g. "GO111MODULE=on go run
		github.com/prometheus/client_golang/examples/random". If built without Go
		module support, all label values will be "unknown". If built with Go module
		support but using the source code from the local file system, the "path" will
		be set appropriately, but "checksum" will be empty and "version" will be
		"(devel)".

		This collector uses only the build information for the main module. See
		https://github.com/povilasv/prommod for an example of a collector for the
		module dependencies.

	 func NewConstHistogram(desc *Desc, count uint64, sum float64, buckets map[float64]uint64, labelValues ...string) (Metric, error)
		NewConstHistogram returns a metric representing a Prometheus histogram with
		fixed values for the count, sum, and bucket counts. As those parameters
		cannot be changed, the returned value does not implement the Histogram
		interface (but only the Metric interface). Users of this package will not
		have much use for it in regular operations. However, when implementing custom
		Collectors, it is useful as a throw-away metric that is generated on the fly
		to send it to Prometheus in the Collect method.

		buckets is a map of upper bounds to cumulative counts, excluding the +Inf
		bucket.

		NewConstHistogram returns an error if the length of labelValues is not
		consistent with the variable labels in Desc or if Desc is invalid.

	 func NewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) (Metric, error)
		NewConstMetric returns a metric with one fixed value that cannot be
		changed. Users of this package will not have much use for it in regular
		operations. However, when implementing custom Collectors, it is useful as a
		throw-away metric that is generated on the fly to send it to Prometheus in
		the Collect method. NewConstMetric returns an error if the length of
		labelValues is not consistent with the variable labels in Desc or if Desc is
		invalid.

	 func NewConstSummary(desc *Desc, count uint64, sum float64, quantiles map[float64]float64, labelValues ...string) (Metric, error)
		NewConstSummary returns a metric representing a Prometheus summary with fixed
		values for the count, sum, and quantiles. As those parameters cannot be
		changed, the returned value does not implement the Summary interface (but
		only the Metric interface). Users of this package will not have much use for
		it in regular operations. However, when implementing custom Collectors, it is
		useful as a throw-away metric that is generated on the fly to send it to
		Prometheus in the Collect method.

		quantiles maps ranks to quantile values. For example, a median latency of
		0.23s and a 99th percentile latency of 0.56s would be expressed as:
		    map[float64]float64{0.5: 0.23, 0.99: 0.56}

		NewConstSummary returns an error if the length of labelValues is not
		consistent with the variable labels in Desc or if Desc is invalid.

	 func NewCounter(opts CounterOpts) Counter
		NewCounter creates a new Counter based on the provided CounterOpts.

		The returned implementation tracks the counter value in two separate
		variables, a float64 and a uint64. The latter is used to track calls of the
		Inc method and calls of the Add method with a value that can be represented
		as a uint64. This allows atomic increments of the counter with optimal
		performance. (It is common to have an Inc call in very hot execution paths.)
		Both internal tracking values are added up in the Write method. This has to
		be taken into account when it comes to precision and overflow behavior.

	 func NewCounterFunc(opts CounterOpts, function func() float64) CounterFunc
		NewCounterFunc creates a new CounterFunc based on the provided
		CounterOpts. The value reported is determined by calling the given function
		from within the Write method. Take into account that metric collection may
		happen concurrently. If that results in concurrent calls to Write, like in
		the case where a CounterFunc is directly registered with Prometheus, the
		provided function must be concurrency-safe. The function should also honor
		the contract for a Counter (values only go up, not down), but compliance will
		not be checked.

	 func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec
		NewCounterVec creates a new CounterVec based on the provided CounterOpts and
		partitioned by the given label names.

	 func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *Desc
		NewDesc allocates and initializes a new Desc. Errors are recorded in the Desc
		and will be reported on registration time. variableLabels and constLabels can
		be nil if no such labels should be set. fqName must not be empty.

		variableLabels only contain the label names. Their label values are variable
		and therefore not part of the Desc. (They are managed within the Metric.)

		For constLabels, the label values are constant. Therefore, they are fully
		specified in the Desc. See the Collector example for a usage pattern.

	 func NewExpvarCollector(exports map[string]*Desc) Collector
		NewExpvarCollector returns a newly allocated expvar Collector that still has
		to be registered with a Prometheus registry.

		An expvar Collector collects metrics from the expvar interface. It provides a
		quick way to expose numeric values that are already exported via expvar as
		Prometheus metrics. Note that the data models of expvar and Prometheus are
		fundamentally different, and that the expvar Collector is inherently slower
		than native Prometheus metrics. Thus, the expvar Collector is probably great
		for experiments and prototying, but you should seriously consider a more
		direct implementation of Prometheus metrics for monitoring production
		systems.

		The exports map has the following meaning:

		The keys in the map correspond to expvar keys, i.e. for every expvar key you
		want to export as Prometheus metric, you need an entry in the exports
		map. The descriptor mapped to each key describes how to export the expvar
		value. It defines the name and the help string of the Prometheus metric
		proxying the expvar value. The type will always be Untyped.

		For descriptors without variable labels, the expvar value must be a number or
		a bool. The number is then directly exported as the Prometheus sample
		value. (For a bool, 'false' translates to 0 and 'true' to 1). Expvar values
		that are not numbers or bools are silently ignored.

		If the descriptor has one variable label, the expvar value must be an expvar
		map. The keys in the expvar map become the various values of the one
		Prometheus label. The values in the expvar map must be numbers or bools again
		as above.

		For descriptors with more than one variable label, the expvar must be a
		nested expvar map, i.e. where the values of the topmost map are maps again
		etc. until a depth is reached that corresponds to the number of labels. The
		leaves of that structure must be numbers or bools as above to serve as the
		sample values.

		Anything that does not fit into the scheme above is silently ignored.

	 func NewGauge(opts GaugeOpts) Gauge
		NewGauge creates a new Gauge based on the provided GaugeOpts.

		The returned implementation is optimized for a fast Set method. If you have a
		choice for managing the value of a Gauge via Set vs. Inc/Dec/Add/Sub, pick
		the former. For example, the Inc method of the returned Gauge is slower than
		the Inc method of a Counter returned by NewCounter. This matches the typical
		scenarios for Gauges and Counters, where the former tends to be Set-heavy and
		the latter Inc-heavy.

	 func NewGaugeFunc(opts GaugeOpts, function func() float64) GaugeFunc
		NewGaugeFunc creates a new GaugeFunc based on the provided GaugeOpts. The
		value reported is determined by calling the given function from within the
		Write method. Take into account that metric collection may happen
		concurrently. Therefore, it must be safe to call the provided function
		concurrently.

		NewGaugeFunc is a good way to create an “info” style metric with a constant
		value of 1. Example:
		https://github.com/prometheus/common/blob/8558a5b7db3c84fa38b4766966059a7bd5bfa2ee/version/info.go#L36-L56

	 func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec
		NewGaugeVec creates a new GaugeVec based on the provided GaugeOpts and
		partitioned by the given label names.

	 func NewGoCollector() Collector
		NewGoCollector returns a collector that exports metrics about the current Go
		process. This includes memory stats. To collect those, runtime.ReadMemStats
		is called. This requires to “stop the world”, which usually only happens for
		garbage collection (GC). Take the following implications into account when
		deciding whether to use the Go collector:

		1. The performance impact of stopping the world is the more relevant the more
		frequently metrics are collected. However, with Go1.9 or later the
		stop-the-world time per metrics collection is very short (~25µs) so that the
		performance impact will only matter in rare cases. However, with older Go
		versions, the stop-the-world duration depends on the heap size and can be
		quite significant (~1.7 ms/GiB as per
		https://go-review.googlesource.com/c/go/+/34937).

		2. During an ongoing GC, nothing else can stop the world. Therefore, if the
		metrics collection happens to coincide with GC, it will only complete after
		GC has finished. Usually, GC is fast enough to not cause problems. However,
		with a very large heap, GC might take multiple seconds, which is enough to
		cause scrape timeouts in common setups. To avoid this problem, the Go
		collector will use the memstats from a previous collection if
		runtime.ReadMemStats takes more than 1s. However, if there are no previously
		collected memstats, or their collection is more than 5m ago, the collection
		will block until runtime.ReadMemStats succeeds. (The problem might be solved
		in Go1.13, see https://github.com/golang/go/issues/19812 for the related Go
		issue.)

	 func NewHistogram(opts HistogramOpts) Histogram
		NewHistogram creates a new Histogram based on the provided HistogramOpts. It
		panics if the buckets in HistogramOpts are not in strictly increasing order.

	 func NewHistogramVec(opts HistogramOpts, labelNames []string) *HistogramVec
		NewHistogramVec creates a new HistogramVec based on the provided HistogramOpts and
		partitioned by the given label names.

	 func NewInvalidDesc(err error) *Desc
		NewInvalidDesc returns an invalid descriptor, i.e. a descriptor with the
		provided error set. If a collector returning such a descriptor is registered,
		registration will fail with the provided error. NewInvalidDesc can be used by
		a Collector to signal inability to describe itself.

	 func NewInvalidMetric(desc *Desc, err error) Metric
		NewInvalidMetric returns a metric whose Write method always returns the
		provided error. It is useful if a Collector finds itself unable to collect
		a metric and wishes to report an error to the registry.

	 func NewMetricWithTimestamp(t time.Time, m Metric) Metric
		NewMetricWithTimestamp returns a new Metric wrapping the provided Metric in a
		way that it has an explicit timestamp set to the provided Time. This is only
		useful in rare cases as the timestamp of a Prometheus metric should usually
		be set by the Prometheus server during scraping. Exceptions include mirroring
		metrics with given timestamps from other metric
		sources.

		NewMetricWithTimestamp works best with MustNewConstMetric,
		MustNewConstHistogram, and MustNewConstSummary, see example.

		Currently, the exposition formats used by Prometheus are limited to
		millisecond resolution. Thus, the provided time will be rounded down to the
		next full millisecond value.

	 func NewPedanticRegistry() *Registry
		NewPedanticRegistry returns a registry that checks during collection if each
		collected Metric is consistent with its reported Desc, and if the Desc has
		actually been registered with the registry. Unchecked Collectors (those whose
		Describe method does not yield any descriptors) are excluded from the check.

		Usually, a Registry will be happy as long as the union of all collected
		Metrics is consistent and valid even if some metrics are not consistent with
		their own Desc or a Desc provided by their registered Collector. Well-behaved
		Collectors and Metrics will only provide consistent Descs. This Registry is
		useful to test the implementation of Collectors and Metrics.

	 func NewProcessCollector(opts ProcessCollectorOpts) Collector
		NewProcessCollector returns a collector which exports the current state of
		process metrics including CPU, memory and file descriptor usage as well as
		the process start time. The detailed behavior is defined by the provided
		ProcessCollectorOpts. The zero value of ProcessCollectorOpts creates a
		collector for the current process with an empty namespace string and no error
		reporting.

		The collector only works on operating systems with a Linux-style proc
		filesystem and on Microsoft Windows. On other operating systems, it will not
		collect any metrics.

	 func NewRegistry() *Registry
		NewRegistry creates a new vanilla Registry without any Collectors
		pre-registered.

	 func NewSummary(opts SummaryOpts) Summary
		NewSummary creates a new Summary based on the provided SummaryOpts.

	 func NewSummaryVec(opts SummaryOpts, labelNames []string) *SummaryVec
		NewSummaryVec creates a new SummaryVec based on the provided SummaryOpts and
		partitioned by the given label names.

		Due to the way a Summary is represented in the Prometheus text format and how
		it is handled by the Prometheus server internally, “quantile” is an illegal
		label name. NewSummaryVec will panic if this label name is used.

	 func NewTimer(o Observer) *Timer
		NewTimer creates a new Timer. The provided Observer is used to observe a
		duration in seconds. Timer is usually used to time a function call in the
		following way:
		   func TimeMe() {
		       timer := NewTimer(myHistogram)
		       defer timer.ObserveDuration()
		       // Do actual work.
		   }

	 func NewUntypedFunc(opts UntypedOpts, function func() float64) UntypedFunc
		NewUntypedFunc creates a new UntypedFunc based on the provided
		UntypedOpts. The value reported is determined by calling the given function
		from within the Write method. Take into account that metric collection may
		happen concurrently. If that results in concurrent calls to Write, like in
		the case where an UntypedFunc is directly registered with Prometheus, the
		provided function must be concurrency-safe.

	 func Register(c Collector) error
		Register registers the provided Collector with the DefaultRegisterer.

		Register is a shortcut for DefaultRegisterer.Register(c). See there for more
		details.

	 func Unregister(c Collector) bool
		Unregister removes the registration of the provided Collector from the
		DefaultRegisterer.

		Unregister is a shortcut for DefaultRegisterer.Unregister(c). See there for
		more details.

	 func WrapRegistererWith(labels Labels, reg Registerer) Registerer
		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.

		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.

		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 WrapRegistererWithPrefix(prefix string, reg Registerer) Registerer
		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.

		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 WriteToTextfile(filename string, g Gatherer) error
		WriteToTextfile calls Gather on the provided Gatherer, encodes the result in the
		Prometheus text format, and writes it to a temporary file. Upon success, the
		temporary file is renamed to the provided filename.

		This is intended for use with the textfile collector of the node exporter.
		Note that the node exporter expects the filename to be suffixed with ".prom".

	/* 28 unexporteds ... *//* 28 unexporteds: */
	 func canCollectProcess() bool
	 func checkDescConsistency(metricFamily *dto.MetricFamily, dtoMetric *dto.Metric, desc *Desc) error
	 func checkLabelName(l string) bool
	 func checkMetricConsistency(metricFamily *dto.MetricFamily, dtoMetric *dto.Metric, metricHashes map[uint64]struct{}) error
		checkMetricConsistency checks if the provided Metric is consistent with the
		provided MetricFamily. It also hashes the Metric labels and the MetricFamily
		name. If the resulting hash is already in the provided metricHashes, an error
		is returned. If not, it is added to metricHashes.

	 func checkSuffixCollisions(mf *dto.MetricFamily, mfs map[string]*dto.MetricFamily) error
		checkSuffixCollisions checks for collisions with the “magic” suffixes the
		Prometheus text format and the internal metric representation of the
		Prometheus server add while flattening Summaries and Histograms.

	 func extractLabelValues(desc *Desc, labels Labels, curry []curriedLabelValue) []string
	 func findMetricWithLabels(desc *Desc, metrics []metricWithLabelValues, labels Labels, curry []curriedLabelValue) int
		findMetricWithLabels returns the index of the matching metric or len(metrics)
		if not found.

	 func findMetricWithLabelValues(metrics []metricWithLabelValues, lvs []string, curry []curriedLabelValue) int
		findMetricWithLabelValues returns the index of the matching metric or
		len(metrics) if not found.

	 func hashAdd(h uint64, s string) uint64
		hashAdd adds a string to a fnv64a hash value, returning the updated hash.

	 func hashAddByte(h uint64, b byte) uint64
		hashAddByte adds a byte to a fnv64a hash value, returning the updated hash.

	 func hashNew() uint64
		hashNew initializies a new fnv64a hash value.

	 func init()
	 func inlineLabelValues(lvs []string, curry []curriedLabelValue) []string
	 func makeInconsistentCardinalityError(fqName string, labels, labelValues []string) error
	 func makeLabelPairs(desc *Desc, labelValues []string) []*dto.LabelPair
	 func matchLabels(desc *Desc, values []string, labels Labels, curry []curriedLabelValue) bool
	 func matchLabelValues(values []string, lvs []string, curry []curriedLabelValue) bool
	 func memstatNamespace(s string) string
	 func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogram
	 func newMetricVec(desc *Desc, newMetric func(lvs ...string) Metric) *metricVec
		newMetricVec returns an initialized metricVec.

	 func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary
	 func newValueFunc(desc *Desc, valueType ValueType, function func() float64) *valueFunc
		newValueFunc returns a newly allocated valueFunc with the given Desc and
		ValueType. The value reported is determined by calling the given function
		from within the Write method. Take into account that metric collection may
		happen concurrently. If that results in concurrent calls to Write, like in
		the case where a valueFunc is directly registered with Prometheus, the
		provided function must be concurrency-safe.

	 func populateMetric(t ValueType, v float64, labelPairs []*dto.LabelPair, m *dto.Metric) error
	 func processMetric(metric Metric, metricFamiliesByName map[string]*dto.MetricFamily, metricHashes map[uint64]struct{}, registeredDescIDs map[uint64]struct{}) error
		processMetric is an internal helper method only used by the Gather method.

	 func readBuildInfo() (path, version, sum string)
		readBuildInfo is a wrapper around debug.ReadBuildInfo for Go 1.12+.

	 func validateLabelValues(vals []string, expectedNumberOfValues int) error
	 func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error
	 func wrapDesc(desc *Desc, prefix string, labels Labels) *Desc
Package-Level Variables (total 8, in which 3 are exported)

	  var DefaultGatherer Gatherer
		DefaultRegisterer and DefaultGatherer are the implementations of the
		Registerer and Gatherer interface a number of convenience functions in this
		package act on. Initially, both variables point to the same Registry, which
		has a process collector (currently on Linux only, see NewProcessCollector)
		and a Go collector (see NewGoCollector, in particular the note about
		stop-the-world implication with Go versions older than 1.9) already
		registered. This approach to keep default instances as global state mirrors
		the approach of other packages in the Go standard library. Note that there
		are caveats. Change the variables with caution and only if you understand the
		consequences. Users who want to avoid global state altogether should not use
		the convenience functions and act on custom instances instead.

	  var DefaultRegisterer Registerer
		DefaultRegisterer and DefaultGatherer are the implementations of the
		Registerer and Gatherer interface a number of convenience functions in this
		package act on. Initially, both variables point to the same Registry, which
		has a process collector (currently on Linux only, see NewProcessCollector)
		and a Go collector (see NewGoCollector, in particular the note about
		stop-the-world implication with Go versions older than 1.9) already
		registered. This approach to keep default instances as global state mirrors
		the approach of other packages in the Go standard library. Note that there
		are caveats. Change the variables with caution and only if you understand the
		consequences. Users who want to avoid global state altogether should not use
		the convenience functions and act on custom instances instead.

	  var DefBuckets []float64
		DefBuckets are the default Histogram buckets. The default buckets are
		tailored to broadly measure the response time (in seconds) of a network
		service. Most likely, however, you will be required to define buckets
		customized to your use case.

	/* 5 unexporteds ... *//* 5 unexporteds: */
	  var defaultRegistry *Registry
		DefaultRegisterer and DefaultGatherer are the implementations of the
		Registerer and Gatherer interface a number of convenience functions in this
		package act on. Initially, both variables point to the same Registry, which
		has a process collector (currently on Linux only, see NewProcessCollector)
		and a Go collector (see NewGoCollector, in particular the note about
		stop-the-world implication with Go versions older than 1.9) already
		registered. This approach to keep default instances as global state mirrors
		the approach of other packages in the Go standard library. Note that there
		are caveats. Change the variables with caution and only if you understand the
		consequences. Users who want to avoid global state altogether should not use
		the convenience functions and act on custom instances instead.

	  var errBucketLabelNotAllowed error
		DefBuckets are the default Histogram buckets. The default buckets are
		tailored to broadly measure the response time (in seconds) of a network
		service. Most likely, however, you will be required to define buckets
		customized to your use case.

	  var errInconsistentCardinality error
	  var errQuantileLabelNotAllowed error
	  var separatorByteSlice []byte // For convenient use with xxhash.
Package-Level Constants (total 13, in which 6 are exported)

	const CounterValue ValueType = 1
		Possible values for the ValueType enum.

	const DefAgeBuckets = 5
		DefAgeBuckets is the default number of buckets used to calculate the
		age of observations.

	const DefBufCap = 500
		DefBufCap is the standard buffer size for collecting Summary observations.

	const DefMaxAge time.Duration = 600000000000
		DefMaxAge is the default duration for which observations stay
		relevant.

	const GaugeValue ValueType = 2
		Possible values for the ValueType enum.

	const UntypedValue ValueType = 3
		Possible values for the ValueType enum.

	/* 7 unexporteds ... *//* 7 unexporteds: */
	const bucketLabel = "le"
		bucketLabel is used for the label that defines the upper bound of a
		bucket of a histogram ("le" -> "less or equal").

	const capDescChan = 10
	const capMetricChan = 1000
		Capacity for the channel to collect metrics and descriptors.

	const offset64 = 14695981039346656037
	const prime64 = 1099511628211
	const quantileLabel = "quantile"
		quantileLabel is used for the label that defines the quantile in a
		summary.

	const reservedLabelPrefix = "__"
		reservedLabelPrefix is a prefix which is not legal in user-supplied
		label names.

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