292 lines
9.8 KiB
Go
292 lines
9.8 KiB
Go
// Copyright 2014 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package prometheus
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import (
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"math"
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"sync/atomic"
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"time"
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dto "github.com/prometheus/client_model/go"
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)
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// Gauge is a Metric that represents a single numerical value that can
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// arbitrarily go up and down.
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//
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// A Gauge is typically used for measured values like temperatures or current
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// memory usage, but also "counts" that can go up and down, like the number of
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// running goroutines.
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//
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// To create Gauge instances, use NewGauge.
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type Gauge interface {
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Metric
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Collector
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// Set sets the Gauge to an arbitrary value.
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Set(float64)
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// Inc increments the Gauge by 1. Use Add to increment it by arbitrary
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// values.
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Inc()
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// Dec decrements the Gauge by 1. Use Sub to decrement it by arbitrary
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// values.
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Dec()
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// Add adds the given value to the Gauge. (The value can be negative,
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// resulting in a decrease of the Gauge.)
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Add(float64)
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// Sub subtracts the given value from the Gauge. (The value can be
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// negative, resulting in an increase of the Gauge.)
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Sub(float64)
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// SetToCurrentTime sets the Gauge to the current Unix time in seconds.
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SetToCurrentTime()
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}
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// GaugeOpts is an alias for Opts. See there for doc comments.
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type GaugeOpts Opts
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// NewGauge creates a new Gauge based on the provided GaugeOpts.
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//
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// The returned implementation is optimized for a fast Set method. If you have a
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// choice for managing the value of a Gauge via Set vs. Inc/Dec/Add/Sub, pick
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// the former. For example, the Inc method of the returned Gauge is slower than
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// the Inc method of a Counter returned by NewCounter. This matches the typical
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// scenarios for Gauges and Counters, where the former tends to be Set-heavy and
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// the latter Inc-heavy.
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func NewGauge(opts GaugeOpts) Gauge {
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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 := &gauge{desc: desc, 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 gauge struct {
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// valBits contains the bits of the represented float64 value. It has
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// to go first in the struct to guarantee alignment for atomic
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// operations. http://golang.org/pkg/sync/atomic/#pkg-note-BUG
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valBits uint64
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selfCollector
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desc *Desc
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labelPairs []*dto.LabelPair
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}
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func (g *gauge) Desc() *Desc {
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return g.desc
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}
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func (g *gauge) Set(val float64) {
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atomic.StoreUint64(&g.valBits, math.Float64bits(val))
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}
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func (g *gauge) SetToCurrentTime() {
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g.Set(float64(time.Now().UnixNano()) / 1e9)
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}
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func (g *gauge) Inc() {
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g.Add(1)
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}
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func (g *gauge) Dec() {
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g.Add(-1)
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}
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func (g *gauge) Add(val float64) {
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for {
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oldBits := atomic.LoadUint64(&g.valBits)
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newBits := math.Float64bits(math.Float64frombits(oldBits) + val)
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if atomic.CompareAndSwapUint64(&g.valBits, oldBits, newBits) {
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return
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}
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}
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}
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func (g *gauge) Sub(val float64) {
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g.Add(val * -1)
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}
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func (g *gauge) Write(out *dto.Metric) error {
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val := math.Float64frombits(atomic.LoadUint64(&g.valBits))
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return populateMetric(GaugeValue, val, g.labelPairs, nil, out)
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}
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// GaugeVec is a Collector that bundles a set of Gauges that all share the same
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// Desc, but have different values for their variable labels. This is used if
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// you want to count the same thing partitioned by various dimensions
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// (e.g. number of operations queued, partitioned by user and operation
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// type). Create instances with NewGaugeVec.
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type GaugeVec struct {
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*MetricVec
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}
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// NewGaugeVec creates a new GaugeVec based on the provided GaugeOpts and
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// partitioned by the given label names.
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func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec {
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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 &GaugeVec{
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MetricVec: NewMetricVec(desc, func(lvs ...string) Metric {
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if len(lvs) != len(desc.variableLabels) {
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panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, lvs))
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}
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result := &gauge{desc: desc, labelPairs: MakeLabelPairs(desc, lvs)}
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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 Gauge for the given slice of label
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// values (same order as the variable labels in Desc). If that combination of
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// label values is accessed for the first time, a new Gauge is created.
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//
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// It is possible to call this method without using the returned Gauge to only
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// create the new Gauge 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 Gauge 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 Gauge from the GaugeVec. In that case, the
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// Gauge will still exist, but it will not be exported anymore, even if a
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// Gauge with the same label values is created later. See also the CounterVec
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// example.
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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 variable labels in Desc (minus any curried labels).
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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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func (v *GaugeVec) GetMetricWithLabelValues(lvs ...string) (Gauge, error) {
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metric, err := v.MetricVec.GetMetricWithLabelValues(lvs...)
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if metric != nil {
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return metric.(Gauge), err
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}
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return nil, err
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}
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// GetMetricWith returns the Gauge for the given Labels map (the label names
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// must match those of the variable labels in Desc). If that label map is
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// accessed for the first time, a new Gauge is created. Implications of
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// creating a Gauge without using it and keeping the Gauge 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 variable labels in Desc (minus any curried labels).
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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 *GaugeVec) GetMetricWith(labels Labels) (Gauge, error) {
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metric, err := v.MetricVec.GetMetricWith(labels)
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if metric != nil {
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return metric.(Gauge), 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. Not returning an
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// error allows shortcuts like
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//
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// myVec.WithLabelValues("404", "GET").Add(42)
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func (v *GaugeVec) WithLabelValues(lvs ...string) Gauge {
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g, 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 g
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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. Not returning an error allows shortcuts like
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//
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// myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Add(42)
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func (v *GaugeVec) With(labels Labels) Gauge {
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g, 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 g
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}
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// CurryWith returns a vector curried with the provided labels, i.e. the
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// returned vector has those labels pre-set for all labeled operations performed
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// on it. The cardinality of the curried vector is reduced accordingly. The
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// order of the remaining labels stays the same (just with the curried labels
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// taken out of the sequence – which is relevant for the
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// (GetMetric)WithLabelValues methods). It is possible to curry a curried
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// vector, but only with labels not yet used for currying before.
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//
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// The metrics contained in the GaugeVec are shared between the curried and
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// uncurried vectors. They are just accessed differently. Curried and uncurried
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// vectors behave identically in terms of collection. Only one must be
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// registered with a given registry (usually the uncurried version). The Reset
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// method deletes all metrics, even if called on a curried vector.
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func (v *GaugeVec) CurryWith(labels Labels) (*GaugeVec, error) {
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vec, err := v.MetricVec.CurryWith(labels)
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if vec != nil {
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return &GaugeVec{vec}, err
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}
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return nil, err
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}
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// MustCurryWith works as CurryWith but panics where CurryWith would have
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// returned an error.
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func (v *GaugeVec) MustCurryWith(labels Labels) *GaugeVec {
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vec, err := v.CurryWith(labels)
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if err != nil {
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panic(err)
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}
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return vec
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}
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// GaugeFunc is a Gauge 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 GaugeFunc instances, use NewGaugeFunc.
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type GaugeFunc interface {
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Metric
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Collector
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}
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// NewGaugeFunc creates a new GaugeFunc based on the provided GaugeOpts. The
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// value reported is determined by calling the given function from within the
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// Write method. Take into account that metric collection may happen
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// concurrently. Therefore, it must be safe to call the provided function
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// concurrently.
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//
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// NewGaugeFunc is a good way to create an “info” style metric with a constant
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// value of 1. Example:
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// https://github.com/prometheus/common/blob/8558a5b7db3c84fa38b4766966059a7bd5bfa2ee/version/info.go#L36-L56
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func NewGaugeFunc(opts GaugeOpts, function func() float64) GaugeFunc {
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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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), GaugeValue, function)
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}
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