306 lines
8.6 KiB
Go
306 lines
8.6 KiB
Go
// Package dogstatsd provides a DogStatsD backend for package metrics. It's very
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// similar to StatsD, but supports arbitrary tags per-metric, which map to Go
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// kit's label values. So, while label values are no-ops in StatsD, they are
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// supported here. For more details, see the documentation at
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// http://docs.datadoghq.com/guides/dogstatsd/.
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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 DogStatsD server
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// over UDP. Emitting one network packet per observation can quickly overwhelm
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// even the fastest internal network.
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package dogstatsd
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import (
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"fmt"
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"io"
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"strings"
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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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// Dogstatsd receives metrics observations and forwards them to a DogStatsD
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// server. Create a Dogstatsd object, use it to create metrics, and pass those
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// metrics as 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 and
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// histograms are 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 DogStatsD server, use the SendLoop helper method.
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type Dogstatsd struct {
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prefix string
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rates *ratemap.RateMap
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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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histograms *lv.Space
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logger log.Logger
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}
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// New returns a Dogstatsd 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) *Dogstatsd {
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return &Dogstatsd{
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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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histograms: 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 Dogstatsd object.
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func (d *Dogstatsd) NewCounter(name string, sampleRate float64) *Counter {
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d.rates.Set(d.prefix+name, sampleRate)
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return &Counter{
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name: d.prefix + name,
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obs: d.counters.Observe,
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}
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}
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// NewGauge returns a gauge, sending observations to this Dogstatsd object.
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func (d *Dogstatsd) NewGauge(name string) *Gauge {
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return &Gauge{
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name: d.prefix + name,
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obs: d.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 Dogstatsd object.
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func (d *Dogstatsd) NewTiming(name string, sampleRate float64) *Timing {
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d.rates.Set(d.prefix+name, sampleRate)
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return &Timing{
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name: d.prefix + name,
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obs: d.timings.Observe,
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}
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}
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// NewHistogram returns a histogram whose observations are of an unspecified
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// unit, and are forwarded to this Dogstatsd object.
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func (d *Dogstatsd) NewHistogram(name string, sampleRate float64) *Histogram {
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d.rates.Set(d.prefix+name, sampleRate)
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return &Histogram{
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name: d.prefix + name,
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obs: d.histograms.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 (d *Dogstatsd) WriteLoop(c <-chan time.Time, w io.Writer) {
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for range c {
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if _, err := d.WriteTo(w); err != nil {
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d.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 (d *Dogstatsd) SendLoop(c <-chan time.Time, network, address string) {
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d.WriteLoop(c, conn.NewDefaultManager(network, address, d.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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// DogStatsD 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 (d *Dogstatsd) WriteTo(w io.Writer) (count int64, err error) {
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var n int
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d.counters.Reset().Walk(func(name string, lvs lv.LabelValues, values []float64) bool {
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n, err = fmt.Fprintf(w, "%s:%f|c%s%s\n", name, sum(values), sampling(d.rates.Get(name)), tagValues(lvs))
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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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d.gauges.Reset().Walk(func(name string, lvs lv.LabelValues, values []float64) bool {
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n, err = fmt.Fprintf(w, "%s:%f|g%s\n", name, last(values), tagValues(lvs))
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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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d.timings.Reset().Walk(func(name string, lvs lv.LabelValues, values []float64) bool {
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sampleRate := d.rates.Get(name)
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for _, value := range values {
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n, err = fmt.Fprintf(w, "%s:%f|ms%s%s\n", name, value, sampling(sampleRate), tagValues(lvs))
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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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d.histograms.Reset().Walk(func(name string, lvs lv.LabelValues, values []float64) bool {
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sampleRate := d.rates.Get(name)
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for _, value := range values {
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n, err = fmt.Fprintf(w, "%s:%f|h%s%s\n", name, value, sampling(sampleRate), tagValues(lvs))
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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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func tagValues(labelValues []string) string {
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if len(labelValues) == 0 {
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return ""
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}
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if len(labelValues)%2 != 0 {
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panic("tagValues received a labelValues with an odd number of strings")
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}
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pairs := make([]string, 0, len(labelValues)/2)
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for i := 0; i < len(labelValues); i += 2 {
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pairs = append(pairs, labelValues[i]+":"+labelValues[i+1])
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}
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return "|#" + strings.Join(pairs, ",")
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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 DogStatsD counter. Observations are forwarded to a Dogstatsd
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// object, and aggregated (summed) per timeseries.
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type Counter struct {
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name string
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lvs lv.LabelValues
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obs observeFunc
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}
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// With implements metrics.Counter.
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func (c *Counter) With(labelValues ...string) metrics.Counter {
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return &Counter{
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name: c.name,
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lvs: c.lvs.With(labelValues...),
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obs: c.obs,
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}
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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, c.lvs, delta)
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}
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// Gauge is a DogStatsD gauge. Observations are forwarded to a Dogstatsd
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// object, and aggregated (the last observation selected) per timeseries.
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type Gauge struct {
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name string
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lvs lv.LabelValues
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obs observeFunc
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}
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// With implements metrics.Gauge.
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func (g *Gauge) With(labelValues ...string) metrics.Gauge {
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return &Gauge{
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name: g.name,
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lvs: g.lvs.With(labelValues...),
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obs: g.obs,
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}
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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, g.lvs, value)
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}
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// Timing is a DogStatsD timing, or metrics.Histogram. Observations are
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// forwarded to a Dogstatsd 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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lvs lv.LabelValues
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obs observeFunc
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}
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// With implements metrics.Timing.
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func (t *Timing) With(labelValues ...string) metrics.Histogram {
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return &Timing{
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name: t.name,
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lvs: t.lvs.With(labelValues...),
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obs: t.obs,
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}
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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, t.lvs, value)
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}
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// Histogram is a DogStatsD histrogram. Observations are forwarded to a
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// Dogstatsd object, and collected (but not aggregated) per timeseries.
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type Histogram struct {
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name string
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lvs lv.LabelValues
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obs observeFunc
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}
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// With implements metrics.Histogram.
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func (h *Histogram) With(labelValues ...string) metrics.Histogram {
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return &Histogram{
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name: h.name,
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lvs: h.lvs.With(labelValues...),
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obs: h.obs,
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}
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}
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// Observe implements metrics.Histogram.
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func (h *Histogram) Observe(value float64) {
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h.obs(h.name, h.lvs, value)
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}
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