198 lines
6.9 KiB
Go
198 lines
6.9 KiB
Go
// Copyright 2014 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package prometheus
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import (
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"errors"
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)
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// Counter is a Metric that represents a single numerical value that only ever
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// goes up. That implies that it cannot be used to count items whose number can
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// also go down, e.g. the number of currently running goroutines. Those
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// "counters" are represented by Gauges.
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//
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// A Counter is typically used to count requests served, tasks completed, errors
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// occurred, etc.
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//
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// To create Counter instances, use NewCounter.
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type Counter interface {
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Metric
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Collector
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// Inc increments the counter by 1. Use Add to increment it by arbitrary
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// non-negative values.
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Inc()
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// Add adds the given value to the counter. It panics if the value is <
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// 0.
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Add(float64)
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}
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// CounterOpts is an alias for Opts. See there for doc comments.
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type CounterOpts Opts
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// NewCounter creates a new Counter based on the provided CounterOpts.
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func NewCounter(opts CounterOpts) Counter {
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desc := NewDesc(
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BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
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opts.Help,
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nil,
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opts.ConstLabels,
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)
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result := &counter{value: value{desc: desc, valType: CounterValue, labelPairs: desc.constLabelPairs}}
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result.init(result) // Init self-collection.
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return result
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}
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type counter struct {
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value
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}
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func (c *counter) Add(v float64) {
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if v < 0 {
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panic(errors.New("counter cannot decrease in value"))
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}
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c.value.Add(v)
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}
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// CounterVec is a Collector that bundles a set of Counters that all share the
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// same Desc, but have different values for their variable labels. This is used
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// if you want to count the same thing partitioned by various dimensions
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// (e.g. number of HTTP requests, partitioned by response code and
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// method). Create instances with NewCounterVec.
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type CounterVec struct {
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*metricVec
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}
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// NewCounterVec creates a new CounterVec based on the provided CounterOpts and
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// partitioned by the given label names.
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func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
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desc := NewDesc(
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BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
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opts.Help,
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labelNames,
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opts.ConstLabels,
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)
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return &CounterVec{
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metricVec: newMetricVec(desc, func(lvs ...string) Metric {
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result := &counter{value: value{
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desc: desc,
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valType: CounterValue,
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labelPairs: makeLabelPairs(desc, lvs),
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}}
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result.init(result) // Init self-collection.
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return result
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}),
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}
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}
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// GetMetricWithLabelValues returns the Counter for the given slice of label
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// values (same order as the VariableLabels in Desc). If that combination of
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// label values is accessed for the first time, a new Counter is created.
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//
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// It is possible to call this method without using the returned Counter to only
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// create the new Counter but leave it at its starting value 0. See also the
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// SummaryVec example.
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//
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// Keeping the Counter for later use is possible (and should be considered if
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// performance is critical), but keep in mind that Reset, DeleteLabelValues and
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// Delete can be used to delete the Counter from the CounterVec. In that case,
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// the Counter will still exist, but it will not be exported anymore, even if a
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// Counter with the same label values is created later.
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//
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// An error is returned if the number of label values is not the same as the
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// number of VariableLabels in Desc.
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//
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// Note that for more than one label value, this method is prone to mistakes
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// caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
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// an alternative to avoid that type of mistake. For higher label numbers, the
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// latter has a much more readable (albeit more verbose) syntax, but it comes
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// with a performance overhead (for creating and processing the Labels map).
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// See also the GaugeVec example.
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func (v *CounterVec) GetMetricWithLabelValues(lvs ...string) (Counter, error) {
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metric, err := v.metricVec.getMetricWithLabelValues(lvs...)
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if metric != nil {
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return metric.(Counter), err
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}
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return nil, err
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}
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// GetMetricWith returns the Counter for the given Labels map (the label names
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// must match those of the VariableLabels in Desc). If that label map is
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// accessed for the first time, a new Counter is created. Implications of
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// creating a Counter without using it and keeping the Counter for later use are
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// the same as for GetMetricWithLabelValues.
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//
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// An error is returned if the number and names of the Labels are inconsistent
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// with those of the VariableLabels in Desc.
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//
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// This method is used for the same purpose as
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// GetMetricWithLabelValues(...string). See there for pros and cons of the two
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// methods.
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func (v *CounterVec) GetMetricWith(labels Labels) (Counter, error) {
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metric, err := v.metricVec.getMetricWith(labels)
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if metric != nil {
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return metric.(Counter), err
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}
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return nil, err
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}
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// WithLabelValues works as GetMetricWithLabelValues, but panics where
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// GetMetricWithLabelValues would have returned an error. By not returning an
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// error, WithLabelValues allows shortcuts like
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// myVec.WithLabelValues("404", "GET").Add(42)
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func (v *CounterVec) WithLabelValues(lvs ...string) Counter {
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c, err := v.GetMetricWithLabelValues(lvs...)
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if err != nil {
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panic(err)
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}
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return c
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}
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// With works as GetMetricWith, but panics where GetMetricWithLabels would have
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// returned an error. By not returning an error, With allows shortcuts like
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// myVec.With(Labels{"code": "404", "method": "GET"}).Add(42)
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func (v *CounterVec) With(labels Labels) Counter {
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c, err := v.GetMetricWith(labels)
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if err != nil {
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panic(err)
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}
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return c
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}
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// CounterFunc is a Counter whose value is determined at collect time by calling a
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// provided function.
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//
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// To create CounterFunc instances, use NewCounterFunc.
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type CounterFunc interface {
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Metric
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Collector
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}
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// NewCounterFunc creates a new CounterFunc based on the provided
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// CounterOpts. The value reported is determined by calling the given function
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// from within the Write method. Take into account that metric collection may
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// happen concurrently. If that results in concurrent calls to Write, like in
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// the case where a CounterFunc is directly registered with Prometheus, the
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// provided function must be concurrency-safe. The function should also honor
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// the contract for a Counter (values only go up, not down), but compliance will
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// not be checked.
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func NewCounterFunc(opts CounterOpts, function func() float64) CounterFunc {
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return newValueFunc(NewDesc(
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BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
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opts.Help,
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nil,
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opts.ConstLabels,
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), CounterValue, function)
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}
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