360 lines
12 KiB
Go
360 lines
12 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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"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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"google.golang.org/protobuf/types/known/timestamppb"
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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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// ExemplarAdder is implemented by Counters that offer the option of adding a
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// value to the Counter together with an exemplar. Its AddWithExemplar method
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// works like the Add method of the Counter interface but also replaces the
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// currently saved exemplar (if any) with a new one, created from the provided
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// value, the current time as timestamp, and the provided labels. Empty Labels
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// will lead to a valid (label-less) exemplar. But if Labels is nil, the current
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// exemplar is left in place. AddWithExemplar panics if the value is < 0, if any
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// of the provided labels are invalid, or if the provided labels contain more
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// than 128 runes in total.
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type ExemplarAdder interface {
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AddWithExemplar(value float64, exemplar Labels)
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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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// CounterVecOpts bundles the options to create a CounterVec metric.
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// It is mandatory to set CounterOpts, see there for mandatory fields. VariableLabels
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// is optional and can safely be left to its default value.
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type CounterVecOpts struct {
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CounterOpts
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// VariableLabels are used to partition the metric vector by the given set
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// of labels. Each label value will be constrained with the optional Contraint
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// function, if provided.
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VariableLabels ConstrainableLabels
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}
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// NewCounter creates a new Counter based on the provided CounterOpts.
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//
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// The returned implementation also implements ExemplarAdder. It is safe to
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// perform the corresponding type assertion.
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//
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// The returned implementation tracks the counter value in two separate
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// variables, a float64 and a uint64. The latter is used to track calls of the
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// Inc method and calls of the Add method with a value that can be represented
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// as a uint64. This allows atomic increments of the counter with optimal
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// performance. (It is common to have an Inc call in very hot execution paths.)
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// Both internal tracking values are added up in the Write method. This has to
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// be taken into account when it comes to precision and overflow behavior.
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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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if opts.now == nil {
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opts.now = time.Now
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}
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result := &counter{desc: desc, labelPairs: desc.constLabelPairs, now: opts.now}
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result.init(result) // Init self-collection.
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result.createdTs = timestamppb.New(opts.now())
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return result
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}
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type counter struct {
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// valBits contains the bits of the represented float64 value, while
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// valInt stores values that are exact integers. Both have to go first
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// in the struct to guarantee alignment for atomic operations.
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// http://golang.org/pkg/sync/atomic/#pkg-note-BUG
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valBits uint64
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valInt uint64
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selfCollector
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desc *Desc
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createdTs *timestamppb.Timestamp
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labelPairs []*dto.LabelPair
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exemplar atomic.Value // Containing nil or a *dto.Exemplar.
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now func() time.Time // For testing, all constructors put time.Now() here.
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}
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func (c *counter) Desc() *Desc {
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return c.desc
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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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ival := uint64(v)
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if float64(ival) == v {
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atomic.AddUint64(&c.valInt, ival)
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return
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}
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for {
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oldBits := atomic.LoadUint64(&c.valBits)
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newBits := math.Float64bits(math.Float64frombits(oldBits) + v)
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if atomic.CompareAndSwapUint64(&c.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 (c *counter) AddWithExemplar(v float64, e Labels) {
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c.Add(v)
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c.updateExemplar(v, e)
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}
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func (c *counter) Inc() {
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atomic.AddUint64(&c.valInt, 1)
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}
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func (c *counter) get() float64 {
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fval := math.Float64frombits(atomic.LoadUint64(&c.valBits))
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ival := atomic.LoadUint64(&c.valInt)
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return fval + float64(ival)
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}
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func (c *counter) Write(out *dto.Metric) error {
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// Read the Exemplar first and the value second. This is to avoid a race condition
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// where users see an exemplar for a not-yet-existing observation.
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var exemplar *dto.Exemplar
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if e := c.exemplar.Load(); e != nil {
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exemplar = e.(*dto.Exemplar)
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}
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val := c.get()
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ct := c.createdTs.AsTime()
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return populateMetric(CounterValue, val, c.labelPairs, exemplar, out, &ct)
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}
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func (c *counter) updateExemplar(v float64, l Labels) {
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if l == nil {
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return
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}
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e, err := newExemplar(v, c.now(), l)
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if err != nil {
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panic(err)
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}
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c.exemplar.Store(e)
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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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return V2.NewCounterVec(CounterVecOpts{
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CounterOpts: opts,
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VariableLabels: UnconstrainedLabels(labelNames),
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})
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}
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// NewCounterVec creates a new CounterVec based on the provided CounterVecOpts.
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func (v2) NewCounterVec(opts CounterVecOpts) *CounterVec {
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desc := V2.NewDesc(
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BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
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opts.Help,
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opts.VariableLabels,
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opts.ConstLabels,
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)
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if opts.now == nil {
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opts.now = time.Now
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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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if len(lvs) != len(desc.variableLabels.names) {
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panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels.names, lvs))
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}
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result := &counter{desc: desc, labelPairs: MakeLabelPairs(desc, lvs), now: time.Now}
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result.init(result) // Init self-collection.
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result.createdTs = timestamppb.New(opts.now())
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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 variable labels 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 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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// 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 variable labels 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 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 *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. 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 *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. 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 *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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// 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 CounterVec 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 *CounterVec) CurryWith(labels Labels) (*CounterVec, error) {
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vec, err := v.MetricVec.CurryWith(labels)
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if vec != nil {
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return &CounterVec{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 *CounterVec) MustCurryWith(labels Labels) *CounterVec {
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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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// 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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//
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// Check out the ExampleGaugeFunc examples for the similar GaugeFunc.
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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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