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+// Copyright 2014 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package prometheus
+
+import (
+ "fmt"
+ "math"
+ "sort"
+ "sync"
+ "time"
+
+ "github.com/beorn7/perks/quantile"
+ "github.com/golang/protobuf/proto"
+
+ dto "github.com/prometheus/client_model/go"
+)
+
+// quantileLabel is used for the label that defines the quantile in a
+// summary.
+const quantileLabel = "quantile"
+
+// 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.
+//
+// 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.
+type Summary interface {
+ Metric
+ Collector
+
+ // Observe adds a single observation to the summary.
+ Observe(float64)
+}
+
+// DefObjectives are the default Summary quantile values.
+//
+// Deprecated: DefObjectives will not be used as the default objectives in
+// v0.10 of the library. The default Summary will have no quantiles then.
+var (
+ DefObjectives = map[float64]float64{0.5: 0.05, 0.9: 0.01, 0.99: 0.001}
+
+ errQuantileLabelNotAllowed = fmt.Errorf(
+ "%q is not allowed as label name in summaries", quantileLabel,
+ )
+)
+
+// Default values for SummaryOpts.
+const (
+ // DefMaxAge is the default duration for which observations stay
+ // relevant.
+ DefMaxAge time.Duration = 10 * time.Minute
+ // DefAgeBuckets is the default number of buckets used to calculate the
+ // age of observations.
+ DefAgeBuckets = 5
+ // DefBufCap is the standard buffer size for collecting Summary observations.
+ DefBufCap = 500
+)
+
+// SummaryOpts bundles the options for creating a Summary metric. It is
+// mandatory to set Name and Help to a non-empty string. All other fields are
+// optional and can safely be left at their zero value.
+type SummaryOpts struct {
+ // 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.
+ Namespace string
+ Subsystem string
+ Name string
+
+ // Help provides information about this Summary. Mandatory!
+ //
+ // Metrics with the same fully-qualified name must have the same Help
+ // string.
+ Help string
+
+ // ConstLabels are used to attach fixed labels to this
+ // Summary. Summaries with the same fully-qualified name must have the
+ // same label names in their ConstLabels.
+ //
+ // Note that in most cases, labels have a value that varies during the
+ // lifetime of a process. Those labels are usually managed with a
+ // SummaryVec. ConstLabels serve only special purposes. One is for the
+ // special case where the value of a label does not change during the
+ // lifetime of a process, e.g. if the revision of the running binary is
+ // put into a label. Another, more advanced purpose is if more than one
+ // Collector needs to collect Summaries with the same fully-qualified
+ // name. In that case, those Summaries must differ in the values of
+ // their ConstLabels. See the Collector examples.
+ //
+ // If the value of a label never changes (not even between binaries),
+ // that label most likely should not be a label at all (but part of the
+ // metric name).
+ ConstLabels Labels
+
+ // 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 DefObjectives. It is used if Objectives is left at
+ // its zero value (i.e. nil). To create a Summary without Objectives,
+ // set it to an empty map (i.e. map[float64]float64{}).
+ //
+ // Deprecated: Note that the current value of DefObjectives is
+ // deprecated. It will be replaced by an empty map in v0.10 of the
+ // library. Please explicitly set Objectives to the desired value.
+ Objectives map[float64]float64
+
+ // MaxAge defines the duration for which an observation stays relevant
+ // for the summary. Must be positive. The default value is DefMaxAge.
+ MaxAge time.Duration
+
+ // 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.
+ AgeBuckets 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").
+ BufCap uint32
+}
+
+// Great fuck-up with the sliding-window decay algorithm... The Merge method of
+// perk/quantile is actually not working as advertised - and it might be
+// unfixable, as the underlying algorithm is apparently not capable of merging
+// summaries in the first place. To avoid using Merge, we are currently adding
+// observations to _each_ age bucket, i.e. the effort to add a sample is
+// essentially multiplied by the number of age buckets. When rotating age
+// buckets, we empty the previous head stream. On scrape time, we simply take
+// the quantiles from the head stream (no merging required). Result: More effort
+// on observation time, less effort on scrape time, which is exactly the
+// opposite of what we try to accomplish, but at least the results are correct.
+//
+// The quite elegant previous contraption to merge the age buckets efficiently
+// on scrape time (see code up commit 6b9530d72ea715f0ba612c0120e6e09fbf1d49d0)
+// can't be used anymore.
+
+// NewSummary creates a new Summary based on the provided SummaryOpts.
+func NewSummary(opts SummaryOpts) Summary {
+ return newSummary(
+ NewDesc(
+ BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
+ opts.Help,
+ nil,
+ opts.ConstLabels,
+ ),
+ opts,
+ )
+}
+
+func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
+ if len(desc.variableLabels) != len(labelValues) {
+ panic(errInconsistentCardinality)
+ }
+
+ for _, n := range desc.variableLabels {
+ if n == quantileLabel {
+ panic(errQuantileLabelNotAllowed)
+ }
+ }
+ for _, lp := range desc.constLabelPairs {
+ if lp.GetName() == quantileLabel {
+ panic(errQuantileLabelNotAllowed)
+ }
+ }
+
+ if opts.Objectives == nil {
+ opts.Objectives = DefObjectives
+ }
+
+ if opts.MaxAge < 0 {
+ panic(fmt.Errorf("illegal max age MaxAge=%v", opts.MaxAge))
+ }
+ if opts.MaxAge == 0 {
+ opts.MaxAge = DefMaxAge
+ }
+
+ if opts.AgeBuckets == 0 {
+ opts.AgeBuckets = DefAgeBuckets
+ }
+
+ if opts.BufCap == 0 {
+ opts.BufCap = DefBufCap
+ }
+
+ s := &summary{
+ desc: desc,
+
+ objectives: opts.Objectives,
+ sortedObjectives: make([]float64, 0, len(opts.Objectives)),
+
+ labelPairs: makeLabelPairs(desc, labelValues),
+
+ hotBuf: make([]float64, 0, opts.BufCap),
+ coldBuf: make([]float64, 0, opts.BufCap),
+ streamDuration: opts.MaxAge / time.Duration(opts.AgeBuckets),
+ }
+ s.headStreamExpTime = time.Now().Add(s.streamDuration)
+ s.hotBufExpTime = s.headStreamExpTime
+
+ for i := uint32(0); i < opts.AgeBuckets; i++ {
+ s.streams = append(s.streams, s.newStream())
+ }
+ s.headStream = s.streams[0]
+
+ for qu := range s.objectives {
+ s.sortedObjectives = append(s.sortedObjectives, qu)
+ }
+ sort.Float64s(s.sortedObjectives)
+
+ s.init(s) // Init self-collection.
+ return s
+}
+
+type summary struct {
+ selfCollector
+
+ bufMtx sync.Mutex // Protects hotBuf and hotBufExpTime.
+ mtx sync.Mutex // Protects every other moving part.
+ // Lock bufMtx before mtx if both are needed.
+
+ desc *Desc
+
+ objectives map[float64]float64
+ sortedObjectives []float64
+
+ labelPairs []*dto.LabelPair
+
+ sum float64
+ cnt uint64
+
+ hotBuf, coldBuf []float64
+
+ streams []*quantile.Stream
+ streamDuration time.Duration
+ headStream *quantile.Stream
+ headStreamIdx int
+ headStreamExpTime, hotBufExpTime time.Time
+}
+
+func (s *summary) Desc() *Desc {
+ return s.desc
+}
+
+func (s *summary) Observe(v float64) {
+ s.bufMtx.Lock()
+ defer s.bufMtx.Unlock()
+
+ now := time.Now()
+ if now.After(s.hotBufExpTime) {
+ s.asyncFlush(now)
+ }
+ s.hotBuf = append(s.hotBuf, v)
+ if len(s.hotBuf) == cap(s.hotBuf) {
+ s.asyncFlush(now)
+ }
+}
+
+func (s *summary) Write(out *dto.Metric) error {
+ sum := &dto.Summary{}
+ qs := make([]*dto.Quantile, 0, len(s.objectives))
+
+ s.bufMtx.Lock()
+ s.mtx.Lock()
+ // Swap bufs even if hotBuf is empty to set new hotBufExpTime.
+ s.swapBufs(time.Now())
+ s.bufMtx.Unlock()
+
+ s.flushColdBuf()
+ sum.SampleCount = proto.Uint64(s.cnt)
+ sum.SampleSum = proto.Float64(s.sum)
+
+ for _, rank := range s.sortedObjectives {
+ var q float64
+ if s.headStream.Count() == 0 {
+ q = math.NaN()
+ } else {
+ q = s.headStream.Query(rank)
+ }
+ qs = append(qs, &dto.Quantile{
+ Quantile: proto.Float64(rank),
+ Value: proto.Float64(q),
+ })
+ }
+
+ s.mtx.Unlock()
+
+ if len(qs) > 0 {
+ sort.Sort(quantSort(qs))
+ }
+ sum.Quantile = qs
+
+ out.Summary = sum
+ out.Label = s.labelPairs
+ return nil
+}
+
+func (s *summary) newStream() *quantile.Stream {
+ return quantile.NewTargeted(s.objectives)
+}
+
+// asyncFlush needs bufMtx locked.
+func (s *summary) asyncFlush(now time.Time) {
+ s.mtx.Lock()
+ s.swapBufs(now)
+
+ // Unblock the original goroutine that was responsible for the mutation
+ // that triggered the compaction. But hold onto the global non-buffer
+ // state mutex until the operation finishes.
+ go func() {
+ s.flushColdBuf()
+ s.mtx.Unlock()
+ }()
+}
+
+// rotateStreams needs mtx AND bufMtx locked.
+func (s *summary) maybeRotateStreams() {
+ for !s.hotBufExpTime.Equal(s.headStreamExpTime) {
+ s.headStream.Reset()
+ s.headStreamIdx++
+ if s.headStreamIdx >= len(s.streams) {
+ s.headStreamIdx = 0
+ }
+ s.headStream = s.streams[s.headStreamIdx]
+ s.headStreamExpTime = s.headStreamExpTime.Add(s.streamDuration)
+ }
+}
+
+// flushColdBuf needs mtx locked.
+func (s *summary) flushColdBuf() {
+ for _, v := range s.coldBuf {
+ for _, stream := range s.streams {
+ stream.Insert(v)
+ }
+ s.cnt++
+ s.sum += v
+ }
+ s.coldBuf = s.coldBuf[0:0]
+ s.maybeRotateStreams()
+}
+
+// swapBufs needs mtx AND bufMtx locked, coldBuf must be empty.
+func (s *summary) swapBufs(now time.Time) {
+ if len(s.coldBuf) != 0 {
+ panic("coldBuf is not empty")
+ }
+ s.hotBuf, s.coldBuf = s.coldBuf, s.hotBuf
+ // hotBuf is now empty and gets new expiration set.
+ for now.After(s.hotBufExpTime) {
+ s.hotBufExpTime = s.hotBufExpTime.Add(s.streamDuration)
+ }
+}
+
+type quantSort []*dto.Quantile
+
+func (s quantSort) Len() int {
+ return len(s)
+}
+
+func (s quantSort) Swap(i, j int) {
+ s[i], s[j] = s[j], s[i]
+}
+
+func (s quantSort) Less(i, j int) bool {
+ return s[i].GetQuantile() < s[j].GetQuantile()
+}
+
+// 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.
+type SummaryVec struct {
+ *MetricVec
+}
+
+// NewSummaryVec creates a new SummaryVec based on the provided SummaryOpts and
+// partitioned by the given label names. At least one label name must be
+// provided.
+func NewSummaryVec(opts SummaryOpts, labelNames []string) *SummaryVec {
+ desc := NewDesc(
+ BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
+ opts.Help,
+ labelNames,
+ opts.ConstLabels,
+ )
+ return &SummaryVec{
+ MetricVec: newMetricVec(desc, func(lvs ...string) Metric {
+ return newSummary(desc, opts, lvs...)
+ }),
+ }
+}
+
+// GetMetricWithLabelValues replaces the method of the same name in
+// MetricVec. The difference is that this method returns a Summary and not a
+// Metric so that no type conversion is required.
+func (m *SummaryVec) GetMetricWithLabelValues(lvs ...string) (Summary, error) {
+ metric, err := m.MetricVec.GetMetricWithLabelValues(lvs...)
+ if metric != nil {
+ return metric.(Summary), err
+ }
+ return nil, err
+}
+
+// GetMetricWith replaces the method of the same name in MetricVec. The
+// difference is that this method returns a Summary and not a Metric so that no
+// type conversion is required.
+func (m *SummaryVec) GetMetricWith(labels Labels) (Summary, error) {
+ metric, err := m.MetricVec.GetMetricWith(labels)
+ if metric != nil {
+ return metric.(Summary), err
+ }
+ return nil, err
+}
+
+// WithLabelValues works as GetMetricWithLabelValues, but panics where
+// GetMetricWithLabelValues would have returned an error. By not returning an
+// error, WithLabelValues allows shortcuts like
+// myVec.WithLabelValues("404", "GET").Observe(42.21)
+func (m *SummaryVec) WithLabelValues(lvs ...string) Summary {
+ return m.MetricVec.WithLabelValues(lvs...).(Summary)
+}
+
+// With works as GetMetricWith, but panics where GetMetricWithLabels would have
+// returned an error. By not returning an error, With allows shortcuts like
+// myVec.With(Labels{"code": "404", "method": "GET"}).Observe(42.21)
+func (m *SummaryVec) With(labels Labels) Summary {
+ return m.MetricVec.With(labels).(Summary)
+}
+
+type constSummary struct {
+ desc *Desc
+ count uint64
+ sum float64
+ quantiles map[float64]float64
+ labelPairs []*dto.LabelPair
+}
+
+func (s *constSummary) Desc() *Desc {
+ return s.desc
+}
+
+func (s *constSummary) Write(out *dto.Metric) error {
+ sum := &dto.Summary{}
+ qs := make([]*dto.Quantile, 0, len(s.quantiles))
+
+ sum.SampleCount = proto.Uint64(s.count)
+ sum.SampleSum = proto.Float64(s.sum)
+
+ for rank, q := range s.quantiles {
+ qs = append(qs, &dto.Quantile{
+ Quantile: proto.Float64(rank),
+ Value: proto.Float64(q),
+ })
+ }
+
+ if len(qs) > 0 {
+ sort.Sort(quantSort(qs))
+ }
+ sum.Quantile = qs
+
+ out.Summary = sum
+ out.Label = s.labelPairs
+
+ return nil
+}
+
+// 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.
+func NewConstSummary(
+ desc *Desc,
+ count uint64,
+ sum float64,
+ quantiles map[float64]float64,
+ labelValues ...string,
+) (Metric, error) {
+ if len(desc.variableLabels) != len(labelValues) {
+ return nil, errInconsistentCardinality
+ }
+ return &constSummary{
+ desc: desc,
+ count: count,
+ sum: sum,
+ quantiles: quantiles,
+ labelPairs: makeLabelPairs(desc, labelValues),
+ }, nil
+}
+
+// MustNewConstSummary is a version of NewConstSummary that panics where
+// NewConstMetric would have returned an error.
+func MustNewConstSummary(
+ desc *Desc,
+ count uint64,
+ sum float64,
+ quantiles map[float64]float64,
+ labelValues ...string,
+) Metric {
+ m, err := NewConstSummary(desc, count, sum, quantiles, labelValues...)
+ if err != nil {
+ panic(err)
+ }
+ return m
+}