232 lines
6.7 KiB
Go
232 lines
6.7 KiB
Go
// Package statsd provides a StatsD backend for package metrics. StatsD has no
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// concept of arbitrary key-value tagging, so label values are not supported,
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// and With is a no-op on all metrics.
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//
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// This package batches observations and emits them on some schedule to the
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// remote server. This is useful even if you connect to your StatsD server over
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// UDP. Emitting one network packet per observation can quickly overwhelm even
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// the fastest internal network.
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package statsd
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import (
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"fmt"
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"io"
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"time"
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"github.com/go-kit/kit/log"
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"github.com/go-kit/kit/metrics"
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"github.com/go-kit/kit/metrics/internal/lv"
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"github.com/go-kit/kit/metrics/internal/ratemap"
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"github.com/go-kit/kit/util/conn"
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)
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// Statsd receives metrics observations and forwards them to a StatsD server.
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// Create a Statsd object, use it to create metrics, and pass those metrics as
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// dependencies to the components that will use them.
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//
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// All metrics are buffered until WriteTo is called. Counters and gauges are
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// aggregated into a single observation per timeseries per write. Timings are
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// buffered but not aggregated.
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//
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// To regularly report metrics to an io.Writer, use the WriteLoop helper method.
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// To send to a StatsD server, use the SendLoop helper method.
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type Statsd struct {
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prefix string
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rates *ratemap.RateMap
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// The observations are collected in an N-dimensional vector space, even
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// though they only take advantage of a single dimension (name). This is an
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// implementation detail born purely from convenience. It would be more
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// accurate to collect them in a map[string][]float64, but we already have
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// this nice data structure and helper methods.
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counters *lv.Space
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gauges *lv.Space
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timings *lv.Space
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logger log.Logger
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}
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// New returns a Statsd object that may be used to create metrics. Prefix is
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// applied to all created metrics. Callers must ensure that regular calls to
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// WriteTo are performed, either manually or with one of the helper methods.
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func New(prefix string, logger log.Logger) *Statsd {
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return &Statsd{
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prefix: prefix,
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rates: ratemap.New(),
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counters: lv.NewSpace(),
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gauges: lv.NewSpace(),
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timings: lv.NewSpace(),
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logger: logger,
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}
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}
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// NewCounter returns a counter, sending observations to this Statsd object.
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func (s *Statsd) NewCounter(name string, sampleRate float64) *Counter {
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s.rates.Set(s.prefix+name, sampleRate)
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return &Counter{
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name: s.prefix + name,
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obs: s.counters.Observe,
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}
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}
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// NewGauge returns a gauge, sending observations to this Statsd object.
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func (s *Statsd) NewGauge(name string) *Gauge {
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return &Gauge{
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name: s.prefix + name,
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obs: s.gauges.Observe,
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}
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}
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// NewTiming returns a histogram whose observations are interpreted as
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// millisecond durations, and are forwarded to this Statsd object.
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func (s *Statsd) NewTiming(name string, sampleRate float64) *Timing {
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s.rates.Set(s.prefix+name, sampleRate)
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return &Timing{
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name: s.prefix + name,
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obs: s.timings.Observe,
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}
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}
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// WriteLoop is a helper method that invokes WriteTo to the passed writer every
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// time the passed channel fires. This method blocks until the channel is
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// closed, so clients probably want to run it in its own goroutine. For typical
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// usage, create a time.Ticker and pass its C channel to this method.
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func (s *Statsd) WriteLoop(c <-chan time.Time, w io.Writer) {
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for range c {
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if _, err := s.WriteTo(w); err != nil {
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s.logger.Log("during", "WriteTo", "err", err)
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}
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}
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}
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// SendLoop is a helper method that wraps WriteLoop, passing a managed
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// connection to the network and address. Like WriteLoop, this method blocks
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// until the channel is closed, so clients probably want to start it in its own
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// goroutine. For typical usage, create a time.Ticker and pass its C channel to
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// this method.
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func (s *Statsd) SendLoop(c <-chan time.Time, network, address string) {
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s.WriteLoop(c, conn.NewDefaultManager(network, address, s.logger))
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}
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// WriteTo flushes the buffered content of the metrics to the writer, in
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// StatsD format. WriteTo abides best-effort semantics, so observations are
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// lost if there is a problem with the write. Clients should be sure to call
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// WriteTo regularly, ideally through the WriteLoop or SendLoop helper methods.
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func (s *Statsd) WriteTo(w io.Writer) (count int64, err error) {
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var n int
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s.counters.Reset().Walk(func(name string, _ lv.LabelValues, values []float64) bool {
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n, err = fmt.Fprintf(w, "%s:%f|c%s\n", name, sum(values), sampling(s.rates.Get(name)))
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if err != nil {
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return false
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}
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count += int64(n)
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return true
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})
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if err != nil {
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return count, err
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}
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s.gauges.Reset().Walk(func(name string, _ lv.LabelValues, values []float64) bool {
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n, err = fmt.Fprintf(w, "%s:%f|g\n", name, last(values))
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if err != nil {
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return false
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}
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count += int64(n)
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return true
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})
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if err != nil {
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return count, err
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}
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s.timings.Reset().Walk(func(name string, _ lv.LabelValues, values []float64) bool {
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sampleRate := s.rates.Get(name)
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for _, value := range values {
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n, err = fmt.Fprintf(w, "%s:%f|ms%s\n", name, value, sampling(sampleRate))
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if err != nil {
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return false
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}
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count += int64(n)
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}
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return true
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})
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if err != nil {
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return count, err
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}
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return count, err
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}
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func sum(a []float64) float64 {
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var v float64
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for _, f := range a {
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v += f
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}
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return v
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}
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func last(a []float64) float64 {
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return a[len(a)-1]
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}
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func sampling(r float64) string {
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var sv string
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if r < 1.0 {
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sv = fmt.Sprintf("|@%f", r)
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}
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return sv
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}
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type observeFunc func(name string, lvs lv.LabelValues, value float64)
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// Counter is a StatsD counter. Observations are forwarded to a Statsd object,
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// and aggregated (summed) per timeseries.
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type Counter struct {
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name string
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obs observeFunc
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}
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// With is a no-op.
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func (c *Counter) With(...string) metrics.Counter {
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return c
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}
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// Add implements metrics.Counter.
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func (c *Counter) Add(delta float64) {
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c.obs(c.name, lv.LabelValues{}, delta)
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}
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// Gauge is a StatsD gauge. Observations are forwarded to a Statsd object, and
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// aggregated (the last observation selected) per timeseries.
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type Gauge struct {
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name string
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obs observeFunc
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}
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// With is a no-op.
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func (g *Gauge) With(...string) metrics.Gauge {
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return g
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}
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// Set implements metrics.Gauge.
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func (g *Gauge) Set(value float64) {
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g.obs(g.name, lv.LabelValues{}, value)
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}
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// Timing is a StatsD timing, or metrics.Histogram. Observations are
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// forwarded to a Statsd object, and collected (but not aggregated) per
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// timeseries.
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type Timing struct {
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name string
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obs observeFunc
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}
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// With is a no-op.
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func (t *Timing) With(...string) metrics.Histogram {
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return t
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}
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// Observe implements metrics.Histogram. Value is interpreted as milliseconds.
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func (t *Timing) Observe(value float64) {
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t.obs(t.name, lv.LabelValues{}, value)
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}
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