Fix duplicated tags in InfluxDB

vendor/github.com/go-kit/kit/metrics/doc.go

@@ -1,23 +1,54 @@
-// Package metrics provides a framework for application instrumentation. All
-// metrics are safe for concurrent use. Considerable design influence has been
-// taken from https://github.com/codahale/metrics and https://prometheus.io.
+// Package metrics provides a framework for application instrumentation. It's
+// primarily designed to help you get started with good and robust
+// instrumentation, and to help you migrate from a less-capable system like
+// Graphite to a more-capable system like Prometheus. If your organization has
+// already standardized on an instrumentation system like Prometheus, and has no
+// plans to change, it may make sense to use that system's instrumentation
+// library directly.
 //
-// This package contains the common interfaces. Your code should take these
-// interfaces as parameters. Implementations are provided for different
-// instrumentation systems in the various subdirectories.
+// This package provides three core metric abstractions (Counter, Gauge, and
+// Histogram) and implementations for almost all common instrumentation
+// backends. Each metric has an observation method (Add, Set, or Observe,
+// respectively) used to record values, and a With method to "scope" the
+// observation by various parameters. For example, you might have a Histogram to
+// record request durations, parameterized by the method that's being called.
+//
+//    var requestDuration metrics.Histogram
+//    // ...
+//    requestDuration.With("method", "MyMethod").Observe(time.Since(begin))
+//
+// This allows a single high-level metrics object (requestDuration) to work with
+// many code paths somewhat dynamically. The concept of With is fully supported
+// in some backends like Prometheus, and not supported in other backends like
+// Graphite. So, With may be a no-op, depending on the concrete implementation
+// you choose. Please check the implementation to know for sure. For
+// implementations that don't provide With, it's necessary to fully parameterize
+// each metric in the metric name, e.g.
+//
+//    // Statsd
+//    c := statsd.NewCounter("request_duration_MyMethod_200")
+//    c.Add(1)
+//
+//    // Prometheus
+//    c := prometheus.NewCounter(stdprometheus.CounterOpts{
+//        Name: "request_duration",
+//        ...
+//    }, []string{"method", "status_code"})
+//    c.With("method", "MyMethod", "status_code", strconv.Itoa(code)).Add(1)
 //
 // Usage
 //
-// Metrics are dependencies and should be passed to the components that need
+// Metrics are dependencies, and should be passed to the components that need
 // them in the same way you'd construct and pass a database handle, or reference
-// to another component. So, create metrics in your func main, using whichever
-// concrete implementation is appropriate for your organization.
+// to another component. Metrics should *not* be created in the global scope.
+// Instead, instantiate metrics in your func main, using whichever concrete
+// implementation is appropriate for your organization.
 //
 //    latency := prometheus.NewSummaryFrom(stdprometheus.SummaryOpts{
 //        Namespace: "myteam",
 //        Subsystem: "foosvc",
 //        Name:      "request_latency_seconds",
-//        Help:      "Incoming request latency in seconds."
+//        Help:      "Incoming request latency in seconds.",
 //    }, []string{"method", "status_code"})
 //
 // Write your components to take the metrics they will use as parameters to
@@ -40,8 +71,14 @@
 //    api := NewAPI(store, logger, latency)
 //    http.ListenAndServe("/", api)
 //
+// Note that metrics are "write-only" interfaces.
+//
 // Implementation details
 //
+// All metrics are safe for concurrent use. Considerable design influence has
+// been taken from https://github.com/codahale/metrics and
+// https://prometheus.io.
+//
 // Each telemetry system has different semantics for label values, push vs.
 // pull, support for histograms, etc. These properties influence the design of
 // their respective packages. This table attempts to summarize the key points of
@@ -54,7 +91,7 @@
 //    expvar      1    atomic                 atomic                 synthetic, batch, in-place expose
 //    influx      n    custom                 custom                 custom
 //    prometheus  n    native                 native                 native
-//    circonus    1    native                 native                 native
 //    pcp         1    native                 native                 native
+//    cloudwatch  n    batch push-aggregate   batch push-aggregate   synthetic, batch, push-aggregate
 //
 package metrics

vendor/github.com/go-kit/kit/metrics/dogstatsd/dogstatsd.go

@@ -14,10 +14,13 @@ import (
 	"fmt"
 	"io"
 	"strings"
+	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/metrics"
+	"github.com/go-kit/kit/metrics/generic"
 	"github.com/go-kit/kit/metrics/internal/lv"
 	"github.com/go-kit/kit/metrics/internal/ratemap"
 	"github.com/go-kit/kit/util/conn"
@@ -34,53 +37,63 @@ import (
 // To regularly report metrics to an io.Writer, use the WriteLoop helper method.
 // To send to a DogStatsD server, use the SendLoop helper method.
 type Dogstatsd struct {
+	mtx        sync.RWMutex
 	prefix     string
 	rates      *ratemap.RateMap
 	counters   *lv.Space
-	gauges     *lv.Space
+	gauges     map[string]*gaugeNode
 	timings    *lv.Space
 	histograms *lv.Space
 	logger     log.Logger
+	lvs        lv.LabelValues
 }
 
 // New returns a Dogstatsd object that may be used to create metrics. Prefix is
 // applied to all created metrics. Callers must ensure that regular calls to
 // WriteTo are performed, either manually or with one of the helper methods.
-func New(prefix string, logger log.Logger) *Dogstatsd {
+func New(prefix string, logger log.Logger, lvs ...string) *Dogstatsd {
+	if len(lvs)%2 != 0 {
+		panic("odd number of LabelValues; programmer error!")
+	}
 	return &Dogstatsd{
 		prefix:     prefix,
 		rates:      ratemap.New(),
 		counters:   lv.NewSpace(),
-		gauges:     lv.NewSpace(),
+		gauges:     map[string]*gaugeNode{},
 		timings:    lv.NewSpace(),
 		histograms: lv.NewSpace(),
 		logger:     logger,
+		lvs:        lvs,
 	}
 }
 
 // NewCounter returns a counter, sending observations to this Dogstatsd object.
 func (d *Dogstatsd) NewCounter(name string, sampleRate float64) *Counter {
-	d.rates.Set(d.prefix+name, sampleRate)
+	d.rates.Set(name, sampleRate)
 	return &Counter{
-		name: d.prefix + name,
+		name: name,
 		obs:  d.counters.Observe,
 	}
 }
 
 // NewGauge returns a gauge, sending observations to this Dogstatsd object.
 func (d *Dogstatsd) NewGauge(name string) *Gauge {
-	return &Gauge{
-		name: d.prefix + name,
-		obs:  d.gauges.Observe,
+	d.mtx.Lock()
+	n, ok := d.gauges[name]
+	if !ok {
+		n = &gaugeNode{gauge: &Gauge{g: generic.NewGauge(name), ddog: d}}
+		d.gauges[name] = n
 	}
+	d.mtx.Unlock()
+	return n.gauge
 }
 
 // NewTiming returns a histogram whose observations are interpreted as
 // millisecond durations, and are forwarded to this Dogstatsd object.
 func (d *Dogstatsd) NewTiming(name string, sampleRate float64) *Timing {
-	d.rates.Set(d.prefix+name, sampleRate)
+	d.rates.Set(name, sampleRate)
 	return &Timing{
-		name: d.prefix + name,
+		name: name,
 		obs:  d.timings.Observe,
 	}
 }
@@ -88,9 +101,9 @@ func (d *Dogstatsd) NewTiming(name string, sampleRate float64) *Timing {
 // NewHistogram returns a histogram whose observations are of an unspecified
 // unit, and are forwarded to this Dogstatsd object.
 func (d *Dogstatsd) NewHistogram(name string, sampleRate float64) *Histogram {
-	d.rates.Set(d.prefix+name, sampleRate)
+	d.rates.Set(name, sampleRate)
 	return &Histogram{
-		name: d.prefix + name,
+		name: name,
 		obs:  d.histograms.Observe,
 	}
 }
@@ -124,7 +137,7 @@ func (d *Dogstatsd) WriteTo(w io.Writer) (count int64, err error) {
 	var n int
 
 	d.counters.Reset().Walk(func(name string, lvs lv.LabelValues, values []float64) bool {
-		n, err = fmt.Fprintf(w, "%s:%f|c%s%s\n", name, sum(values), sampling(d.rates.Get(name)), tagValues(lvs))
+		n, err = fmt.Fprintf(w, "%s%s:%f|c%s%s\n", d.prefix, name, sum(values), sampling(d.rates.Get(name)), d.tagValues(lvs))
 		if err != nil {
 			return false
 		}
@@ -135,22 +148,23 @@ func (d *Dogstatsd) WriteTo(w io.Writer) (count int64, err error) {
 		return count, err
 	}
 
-	d.gauges.Reset().Walk(func(name string, lvs lv.LabelValues, values []float64) bool {
-		n, err = fmt.Fprintf(w, "%s:%f|g%s\n", name, last(values), tagValues(lvs))
-		if err != nil {
-			return false
-		}
-		count += int64(n)
-		return true
-	})
-	if err != nil {
-		return count, err
+	d.mtx.RLock()
+	for _, root := range d.gauges {
+		root.walk(func(name string, lvs lv.LabelValues, value float64) bool {
+			n, err = fmt.Fprintf(w, "%s%s:%f|g%s\n", d.prefix, name, value, d.tagValues(lvs))
+			if err != nil {
+				return false
+			}
+			count += int64(n)
+			return true
+		})
 	}
+	d.mtx.RUnlock()
 
 	d.timings.Reset().Walk(func(name string, lvs lv.LabelValues, values []float64) bool {
 		sampleRate := d.rates.Get(name)
 		for _, value := range values {
-			n, err = fmt.Fprintf(w, "%s:%f|ms%s%s\n", name, value, sampling(sampleRate), tagValues(lvs))
+			n, err = fmt.Fprintf(w, "%s%s:%f|ms%s%s\n", d.prefix, name, value, sampling(sampleRate), d.tagValues(lvs))
 			if err != nil {
 				return false
 			}
@@ -165,7 +179,7 @@ func (d *Dogstatsd) WriteTo(w io.Writer) (count int64, err error) {
 	d.histograms.Reset().Walk(func(name string, lvs lv.LabelValues, values []float64) bool {
 		sampleRate := d.rates.Get(name)
 		for _, value := range values {
-			n, err = fmt.Fprintf(w, "%s:%f|h%s%s\n", name, value, sampling(sampleRate), tagValues(lvs))
+			n, err = fmt.Fprintf(w, "%s%s:%f|h%s%s\n", d.prefix, name, value, sampling(sampleRate), d.tagValues(lvs))
 			if err != nil {
 				return false
 			}
@@ -200,14 +214,17 @@ func sampling(r float64) string {
 	return sv
 }
 
-func tagValues(labelValues []string) string {
-	if len(labelValues) == 0 {
+func (d *Dogstatsd) tagValues(labelValues []string) string {
+	if len(labelValues) == 0 && len(d.lvs) == 0 {
 		return ""
 	}
 	if len(labelValues)%2 != 0 {
 		panic("tagValues received a labelValues with an odd number of strings")
 	}
-	pairs := make([]string, 0, len(labelValues)/2)
+	pairs := make([]string, 0, (len(d.lvs)+len(labelValues))/2)
+	for i := 0; i < len(d.lvs); i += 2 {
+		pairs = append(pairs, d.lvs[i]+":"+d.lvs[i+1])
+	}
 	for i := 0; i < len(labelValues); i += 2 {
 		pairs = append(pairs, labelValues[i]+":"+labelValues[i+1])
 	}
@@ -241,23 +258,31 @@ func (c *Counter) Add(delta float64) {
 // Gauge is a DogStatsD gauge. Observations are forwarded to a Dogstatsd
 // object, and aggregated (the last observation selected) per timeseries.
 type Gauge struct {
-	name string
-	lvs  lv.LabelValues
-	obs  observeFunc
+	g    *generic.Gauge
+	ddog *Dogstatsd
+	set  int32
 }
 
 // With implements metrics.Gauge.
 func (g *Gauge) With(labelValues ...string) metrics.Gauge {
-	return &Gauge{
-		name: g.name,
-		lvs:  g.lvs.With(labelValues...),
-		obs:  g.obs,
-	}
+	g.ddog.mtx.RLock()
+	node := g.ddog.gauges[g.g.Name]
+	g.ddog.mtx.RUnlock()
+
+	ga := &Gauge{g: g.g.With(labelValues...).(*generic.Gauge), ddog: g.ddog}
+	return node.addGauge(ga, ga.g.LabelValues())
 }
 
 // Set implements metrics.Gauge.
 func (g *Gauge) Set(value float64) {
-	g.obs(g.name, g.lvs, value)
+	g.g.Set(value)
+	g.touch()
+}
+
+// Add implements metrics.Gauge.
+func (g *Gauge) Add(delta float64) {
+	g.g.Add(delta)
+	g.touch()
 }
 
 // Timing is a DogStatsD timing, or metrics.Histogram. Observations are
@@ -304,3 +329,61 @@ func (h *Histogram) With(labelValues ...string) metrics.Histogram {
 func (h *Histogram) Observe(value float64) {
 	h.obs(h.name, h.lvs, value)
 }
+
+type pair struct{ label, value string }
+
+type gaugeNode struct {
+	mtx      sync.RWMutex
+	gauge    *Gauge
+	children map[pair]*gaugeNode
+}
+
+func (n *gaugeNode) addGauge(g *Gauge, lvs lv.LabelValues) *Gauge {
+	n.mtx.Lock()
+	defer n.mtx.Unlock()
+	if len(lvs) == 0 {
+		if n.gauge == nil {
+			n.gauge = g
+		}
+		return n.gauge
+	}
+	if len(lvs) < 2 {
+		panic("too few LabelValues; programmer error!")
+	}
+	head, tail := pair{lvs[0], lvs[1]}, lvs[2:]
+	if n.children == nil {
+		n.children = map[pair]*gaugeNode{}
+	}
+	child, ok := n.children[head]
+	if !ok {
+		child = &gaugeNode{}
+		n.children[head] = child
+	}
+	return child.addGauge(g, tail)
+}
+
+func (n *gaugeNode) walk(fn func(string, lv.LabelValues, float64) bool) bool {
+	n.mtx.RLock()
+	defer n.mtx.RUnlock()
+	if n.gauge != nil {
+		value, ok := n.gauge.read()
+		if ok && !fn(n.gauge.g.Name, n.gauge.g.LabelValues(), value) {
+			return false
+		}
+	}
+	for _, child := range n.children {
+		if !child.walk(fn) {
+			return false
+		}
+	}
+	return true
+}
+
+func (g *Gauge) touch() {
+	atomic.StoreInt32(&(g.set), 1)
+}
+
+func (g *Gauge) read() (float64, bool) {
+	set := atomic.SwapInt32(&(g.set), 0)
+	return g.g.Value(), set != 0
+}

vendor/github.com/go-kit/kit/metrics/generic/generic.go

@@ -33,6 +33,7 @@ func NewCounter(name string) *Counter {
 // With implements Counter.
 func (c *Counter) With(labelValues ...string) metrics.Counter {
 	return &Counter{
+		Name: c.Name,
 		bits: atomic.LoadUint64(&c.bits),
 		lvs:  c.lvs.With(labelValues...),
 	}
@@ -95,6 +96,7 @@ func NewGauge(name string) *Gauge {
 // With implements Gauge.
 func (g *Gauge) With(labelValues ...string) metrics.Gauge {
 	return &Gauge{
+		Name: g.Name,
 		bits: atomic.LoadUint64(&g.bits),
 		lvs:  g.lvs.With(labelValues...),
 	}
@@ -105,6 +107,20 @@ func (g *Gauge) Set(value float64) {
 	atomic.StoreUint64(&g.bits, math.Float64bits(value))
 }
 
+// Add implements metrics.Gauge.
+func (g *Gauge) Add(delta float64) {
+	for {
+		var (
+			old  = atomic.LoadUint64(&g.bits)
+			newf = math.Float64frombits(old) + delta
+			new  = math.Float64bits(newf)
+		)
+		if atomic.CompareAndSwapUint64(&g.bits, old, new) {
+			break
+		}
+	}
+}
+
 // Value returns the current value of the gauge.
 func (g *Gauge) Value() float64 {
 	return math.Float64frombits(atomic.LoadUint64(&g.bits))
@@ -121,7 +137,7 @@ func (g *Gauge) LabelValues() []string {
 type Histogram struct {
 	Name string
 	lvs  lv.LabelValues
-	h    gohistogram.Histogram
+	h    *safeHistogram
 }
 
 // NewHistogram returns a numeric histogram based on VividCortex/gohistogram. A
@@ -129,25 +145,30 @@ type Histogram struct {
 func NewHistogram(name string, buckets int) *Histogram {
 	return &Histogram{
 		Name: name,
-		h:    gohistogram.NewHistogram(buckets),
+		h:    &safeHistogram{Histogram: gohistogram.NewHistogram(buckets)},
 	}
 }
 
 // With implements Histogram.
 func (h *Histogram) With(labelValues ...string) metrics.Histogram {
 	return &Histogram{
-		lvs: h.lvs.With(labelValues...),
-		h:   h.h,
+		Name: h.Name,
+		lvs:  h.lvs.With(labelValues...),
+		h:    h.h,
 	}
 }
 
 // Observe implements Histogram.
 func (h *Histogram) Observe(value float64) {
+	h.h.Lock()
+	defer h.h.Unlock()
 	h.h.Add(value)
 }
 
 // Quantile returns the value of the quantile q, 0.0 < q < 1.0.
 func (h *Histogram) Quantile(q float64) float64 {
+	h.h.RLock()
+	defer h.h.RUnlock()
 	return h.h.Quantile(q)
 }
 
@@ -159,9 +180,17 @@ func (h *Histogram) LabelValues() []string {
 // Print writes a string representation of the histogram to the passed writer.
 // Useful for printing to a terminal.
 func (h *Histogram) Print(w io.Writer) {
+	h.h.RLock()
+	defer h.h.RUnlock()
 	fmt.Fprintf(w, h.h.String())
 }
 
+// safeHistogram exists as gohistogram.Histogram is not goroutine-safe.
+type safeHistogram struct {
+	sync.RWMutex
+	gohistogram.Histogram
+}
+
 // Bucket is a range in a histogram which aggregates observations.
 type Bucket struct {
 	From, To, Count int64

vendor/github.com/go-kit/kit/metrics/influx/influx.go

@@ -66,6 +66,7 @@ func (in *Influx) NewGauge(name string) *Gauge {
 	return &Gauge{
 		name: name,
 		obs:  in.gauges.Observe,
+		add:  in.gauges.Add,
 	}
 }
 
@@ -168,10 +169,14 @@ func mergeTags(tags map[string]string, labelValues []string) map[string]string {
 	if len(labelValues)%2 != 0 {
 		panic("mergeTags received a labelValues with an odd number of strings")
 	}
-	for i := 0; i < len(labelValues); i += 2 {
-		tags[labelValues[i]] = labelValues[i+1]
+	ret := make(map[string]string, len(tags)+len(labelValues)/2)
+	for k, v := range tags {
+		ret[k] = v
 	}
-	return tags
+	for i := 0; i < len(labelValues); i += 2 {
+		ret[labelValues[i]] = labelValues[i+1]
+	}
+	return ret
 }
 
 func sum(a []float64) float64 {
@@ -216,6 +221,7 @@ type Gauge struct {
 	name string
 	lvs  lv.LabelValues
 	obs  observeFunc
+	add  observeFunc
 }
 
 // With implements metrics.Gauge.
@@ -224,6 +230,7 @@ func (g *Gauge) With(labelValues ...string) metrics.Gauge {
 		name: g.name,
 		lvs:  g.lvs.With(labelValues...),
 		obs:  g.obs,
+		add:  g.add,
 	}
 }
 
@@ -232,6 +239,11 @@ func (g *Gauge) Set(value float64) {
 	g.obs(g.name, g.lvs, value)
 }
 
+// Add implements metrics.Gauge.
+func (g *Gauge) Add(delta float64) {
+	g.add(g.name, g.lvs, delta)
+}
+
 // Histogram is an Influx histrogram. Observations are aggregated into a
 // generic.Histogram and emitted as per-quantile gauges to the Influx server.
 type Histogram struct {

vendor/github.com/go-kit/kit/metrics/internal/lv/space.go

@@ -21,6 +21,13 @@ func (s *Space) Observe(name string, lvs LabelValues, value float64) {
 	s.nodeFor(name).observe(lvs, value)
 }
 
+// Add locates the time series identified by the name and label values in
+// the vector space, and appends the delta to the last value in the list of
+// observations.
+func (s *Space) Add(name string, lvs LabelValues, delta float64) {
+	s.nodeFor(name).add(lvs, delta)
+}
+
 // Walk traverses the vector space and invokes fn for each non-empty time series
 // which is encountered. Return false to abort the traversal.
 func (s *Space) Walk(fn func(name string, lvs LabelValues, observations []float64) bool) {
@@ -91,6 +98,34 @@ func (n *node) observe(lvs LabelValues, value float64) {
 	child.observe(tail, value)
 }
 
+func (n *node) add(lvs LabelValues, delta float64) {
+	n.mtx.Lock()
+	defer n.mtx.Unlock()
+	if len(lvs) == 0 {
+		var value float64
+		if len(n.observations) > 0 {
+			value = last(n.observations) + delta
+		} else {
+			value = delta
+		}
+		n.observations = append(n.observations, value)
+		return
+	}
+	if len(lvs) < 2 {
+		panic("too few LabelValues; programmer error!")
+	}
+	head, tail := pair{lvs[0], lvs[1]}, lvs[2:]
+	if n.children == nil {
+		n.children = map[pair]*node{}
+	}
+	child, ok := n.children[head]
+	if !ok {
+		child = &node{}
+		n.children[head] = child
+	}
+	child.add(tail, delta)
+}
+
 func (n *node) walk(lvs LabelValues, fn func(LabelValues, []float64) bool) bool {
 	n.mtx.RLock()
 	defer n.mtx.RUnlock()
@@ -104,3 +139,7 @@ func (n *node) walk(lvs LabelValues, fn func(LabelValues, []float64) bool) bool
 	}
 	return true
 }
+
+func last(a []float64) float64 {
+	return a[len(a)-1]
+}

vendor/github.com/go-kit/kit/metrics/metrics.go

@@ -12,6 +12,7 @@ type Counter interface {
 type Gauge interface {
 	With(labelValues ...string) Gauge
 	Set(value float64)
+	Add(delta float64)
 }
 
 // Histogram describes a metric that takes repeated observations of the same

vendor/github.com/go-kit/kit/metrics/multi/multi.go

@@ -54,6 +54,13 @@ func (g Gauge) With(labelValues ...string) metrics.Gauge {
 	return next
 }
 
+// Add implements metrics.Gauge.
+func (g Gauge) Add(delta float64) {
+	for _, gauge := range g {
+		gauge.Add(delta)
+	}
+}
+
 // Histogram collects multiple individual histograms and treats them as a unit.
 type Histogram []metrics.Histogram
 

vendor/github.com/go-kit/kit/metrics/statsd/statsd.go

@@ -74,6 +74,7 @@ func (s *Statsd) NewGauge(name string) *Gauge {
 	return &Gauge{
 		name: s.prefix + name,
 		obs:  s.gauges.Observe,
+		add:  s.gauges.Add,
 	}
 }
 
@@ -201,6 +202,7 @@ func (c *Counter) Add(delta float64) {
 type Gauge struct {
 	name string
 	obs  observeFunc
+	add  observeFunc
 }
 
 // With is a no-op.
@@ -213,6 +215,11 @@ func (g *Gauge) Set(value float64) {
 	g.obs(g.name, lv.LabelValues{}, value)
 }
 
+// Add implements metrics.Gauge.
+func (g *Gauge) Add(delta float64) {
+	g.add(g.name, lv.LabelValues{}, delta)
+}
+
 // Timing is a StatsD timing, or metrics.Histogram. Observations are
 // forwarded to a Statsd object, and collected (but not aggregated) per
 // timeseries.

vendor/github.com/go-kit/kit/metrics/timer.go

@@ -7,6 +7,7 @@ import "time"
 type Timer struct {
 	h Histogram
 	t time.Time
+	u time.Duration
 }
 
 // NewTimer wraps the given histogram and records the current time.
@@ -14,15 +15,22 @@ func NewTimer(h Histogram) *Timer {
 	return &Timer{
 		h: h,
 		t: time.Now(),
+		u: time.Second,
 	}
 }
 
 // ObserveDuration captures the number of seconds since the timer was
 // constructed, and forwards that observation to the histogram.
 func (t *Timer) ObserveDuration() {
-	d := time.Since(t.t).Seconds()
+	d := float64(time.Since(t.t).Nanoseconds()) / float64(t.u)
 	if d < 0 {
 		d = 0
 	}
 	t.h.Observe(d)
 }
+
+// Unit sets the unit of the float64 emitted by the timer.
+// By default, the timer emits seconds.
+func (t *Timer) Unit(u time.Duration) {
+	t.u = u
+}