metrics: split Gauge interface, fix tests, fix race on Sample

core/state/statedb.go

@@ -1103,12 +1103,10 @@ func (s *StateDB) deleteStorage(addr common.Address, addrHash common.Hash, root
 			slotDeletionSkip.Inc(1)
 		}
 		n := int64(len(slots))
-		if n > slotDeletionMaxCount.Value() {
+
-			slotDeletionMaxCount.Update(n)
+		slotDeletionMaxCount.UpdateIfGt(int64(len(slots)))
-		}
+		slotDeletionMaxSize.UpdateIfGt(int64(size))
-		if int64(size) > slotDeletionMaxSize.Value() {
+
-			slotDeletionMaxSize.Update(int64(size))
-		}
 		slotDeletionTimer.UpdateSince(start)
 		slotDeletionCount.Mark(n)
 		slotDeletionSize.Mark(int64(size))

metrics/exp/exp.go

@@ -119,7 +119,7 @@ func (exp *exp) publishCounterFloat64(name string, metric metrics.CounterFloat64
 	v.Set(metric.Count())
 }
 
-func (exp *exp) publishGauge(name string, metric metrics.Gauge) {
+func (exp *exp) publishGauge(name string, metric metrics.GaugeSnapshot) {
 	v := exp.getInt(name)
 	v.Set(metric.Value())
 }
@@ -193,7 +193,7 @@ func (exp *exp) syncToExpvar() {
 		case metrics.CounterFloat64:
 			exp.publishCounterFloat64(name, i)
 		case metrics.Gauge:
-			exp.publishGauge(name, i)
+			exp.publishGauge(name, i.Snapshot())
 		case metrics.GaugeFloat64:
 			exp.publishGaugeFloat64(name, i)
 		case metrics.GaugeInfo:

metrics/gauge.go

@@ -2,13 +2,18 @@ package metrics
 
 import "sync/atomic"
 
+// gaugeSnapshot contains a readonly int64.
+type GaugeSnapshot interface {
+	Value() int64
+}
+
 // Gauges hold an int64 value that can be set arbitrarily.
 type Gauge interface {
-	Snapshot() Gauge
+	Snapshot() GaugeSnapshot
 	Update(int64)
+	UpdateIfGt(int64)
 	Dec(int64)
 	Inc(int64)
-	Value() int64
 }
 
 // GetOrRegisterGauge returns an existing Gauge or constructs and registers a
@@ -38,57 +43,23 @@ func NewRegisteredGauge(name string, r Registry) Gauge {
 	return c
 }
 
-// NewFunctionalGauge constructs a new FunctionalGauge.
+// gaugeSnapshot is a read-only copy of another Gauge.
-func NewFunctionalGauge(f func() int64) Gauge {
+type gaugeSnapshot int64
-	if !Enabled {
-		return NilGauge{}
-	}
-	return &FunctionalGauge{value: f}
-}
-
-// NewRegisteredFunctionalGauge constructs and registers a new StandardGauge.
-func NewRegisteredFunctionalGauge(name string, r Registry, f func() int64) Gauge {
-	c := NewFunctionalGauge(f)
-	if nil == r {
-		r = DefaultRegistry
-	}
-	r.Register(name, c)
-	return c
-}
-
-// GaugeSnapshot is a read-only copy of another Gauge.
-type GaugeSnapshot int64
-
-// Snapshot returns the snapshot.
-func (g GaugeSnapshot) Snapshot() Gauge { return g }
-
-// Update panics.
-func (GaugeSnapshot) Update(int64) {
-	panic("Update called on a GaugeSnapshot")
-}
-
-// Dec panics.
-func (GaugeSnapshot) Dec(int64) {
-	panic("Dec called on a GaugeSnapshot")
-}
-
-// Inc panics.
-func (GaugeSnapshot) Inc(int64) {
-	panic("Inc called on a GaugeSnapshot")
-}
 
 // Value returns the value at the time the snapshot was taken.
-func (g GaugeSnapshot) Value() int64 { return int64(g) }
+func (g gaugeSnapshot) Value() int64 { return int64(g) }
 
 // NilGauge is a no-op Gauge.
 type NilGauge struct{}
 
 // Snapshot is a no-op.
-func (NilGauge) Snapshot() Gauge { return NilGauge{} }
+func (NilGauge) Snapshot() GaugeSnapshot { return NilGauge{} }
 
 // Update is a no-op.
 func (NilGauge) Update(v int64) {}
 
+func (NilGauge) UpdateIfGt(v int64) {}
+
 // Dec is a no-op.
 func (NilGauge) Dec(i int64) {}
 
@@ -105,8 +76,8 @@ type StandardGauge struct {
 }
 
 // Snapshot returns a read-only copy of the gauge.
-func (g *StandardGauge) Snapshot() Gauge {
+func (g *StandardGauge) Snapshot() GaugeSnapshot {
-	return GaugeSnapshot(g.Value())
+	return gaugeSnapshot(g.value.Load())
 }
 
 // Update updates the gauge's value.
@@ -114,9 +85,11 @@ func (g *StandardGauge) Update(v int64) {
 	g.value.Store(v)
 }
 
-// Value returns the gauge's current value.
+// Update updates the gauge's value if v is larger then the current valie.
-func (g *StandardGauge) Value() int64 {
+func (g *StandardGauge) UpdateIfGt(v int64) {
-	return g.value.Load()
+	if g.value.Load() < v {
+		g.value.Store(v)
+	}
 }
 
 // Dec decrements the gauge's current value by the given amount.
@@ -128,31 +101,3 @@ func (g *StandardGauge) Dec(i int64) {
 func (g *StandardGauge) Inc(i int64) {
 	g.value.Add(i)
 }
-
-// FunctionalGauge returns value from given function
-type FunctionalGauge struct {
-	value func() int64
-}
-
-// Value returns the gauge's current value.
-func (g FunctionalGauge) Value() int64 {
-	return g.value()
-}
-
-// Snapshot returns the snapshot.
-func (g FunctionalGauge) Snapshot() Gauge { return GaugeSnapshot(g.Value()) }
-
-// Update panics.
-func (FunctionalGauge) Update(int64) {
-	panic("Update called on a FunctionalGauge")
-}
-
-// Dec panics.
-func (FunctionalGauge) Dec(int64) {
-	panic("Dec called on a FunctionalGauge")
-}
-
-// Inc panics.
-func (FunctionalGauge) Inc(int64) {
-	panic("Inc called on a FunctionalGauge")
-}

metrics/gauge_test.go

@@ -1,7 +1,6 @@
 package metrics
 
 import (
-	"fmt"
 	"testing"
 )
 
@@ -13,14 +12,6 @@ func BenchmarkGauge(b *testing.B) {
 	}
 }
 
-func TestGauge(t *testing.T) {
-	g := NewGauge()
-	g.Update(int64(47))
-	if v := g.Value(); v != 47 {
-		t.Errorf("g.Value(): 47 != %v\n", v)
-	}
-}
-
 func TestGaugeSnapshot(t *testing.T) {
 	g := NewGauge()
 	g.Update(int64(47))
@@ -34,35 +25,7 @@ func TestGaugeSnapshot(t *testing.T) {
 func TestGetOrRegisterGauge(t *testing.T) {
 	r := NewRegistry()
 	NewRegisteredGauge("foo", r).Update(47)
-	if g := GetOrRegisterGauge("foo", r); g.Value() != 47 {
+	if g := GetOrRegisterGauge("foo", r); g.Snapshot().Value() != 47 {
 		t.Fatal(g)
 	}
 }
-
-func TestFunctionalGauge(t *testing.T) {
-	var counter int64
-	fg := NewFunctionalGauge(func() int64 {
-		counter++
-		return counter
-	})
-	fg.Value()
-	fg.Value()
-	if counter != 2 {
-		t.Error("counter != 2")
-	}
-}
-
-func TestGetOrRegisterFunctionalGauge(t *testing.T) {
-	r := NewRegistry()
-	NewRegisteredFunctionalGauge("foo", r, func() int64 { return 47 })
-	if g := GetOrRegisterGauge("foo", r); g.Value() != 47 {
-		t.Fatal(g)
-	}
-}
-
-func ExampleGetOrRegisterGauge() {
-	m := "server.bytes_sent"
-	g := GetOrRegisterGauge(m, nil)
-	g.Update(47)
-	fmt.Println(g.Value()) // Output: 47
-}

metrics/graphite.go

@@ -70,7 +70,7 @@ func graphite(c *GraphiteConfig) error {
 		case CounterFloat64:
 			fmt.Fprintf(w, "%s.%s.count %f %d\n", c.Prefix, name, metric.Count(), now)
 		case Gauge:
-			fmt.Fprintf(w, "%s.%s.value %d %d\n", c.Prefix, name, metric.Value(), now)
+			fmt.Fprintf(w, "%s.%s.value %d %d\n", c.Prefix, name, metric.Snapshot().Value(), now)
 		case GaugeFloat64:
 			fmt.Fprintf(w, "%s.%s.value %f %d\n", c.Prefix, name, metric.Value(), now)
 		case GaugeInfo:

metrics/histogram_test.go

@@ -14,7 +14,7 @@ func TestGetOrRegisterHistogram(t *testing.T) {
 	r := NewRegistry()
 	s := NewUniformSample(100)
 	NewRegisteredHistogram("foo", r, s).Update(47)
-	if h := GetOrRegisterHistogram("foo", r, s); h.Count() != 1 {
+	if h := GetOrRegisterHistogram("foo", r, s).Snapshot(); h.Count() != 1 {
 		t.Fatal(h)
 	}
 }
@@ -24,11 +24,11 @@ func TestHistogram10000(t *testing.T) {
 	for i := 1; i <= 10000; i++ {
 		h.Update(int64(i))
 	}
-	testHistogram10000(t, h)
+	testHistogram10000(t, h.Snapshot())
 }
 
 func TestHistogramEmpty(t *testing.T) {
-	h := NewHistogram(NewUniformSample(100))
+	h := NewHistogram(NewUniformSample(100)).Snapshot()
 	if count := h.Count(); count != 0 {
 		t.Errorf("h.Count(): 0 != %v\n", count)
 	}
@@ -66,7 +66,7 @@ func TestHistogramSnapshot(t *testing.T) {
 	testHistogram10000(t, snapshot)
 }
 
-func testHistogram10000(t *testing.T, h Histogram) {
+func testHistogram10000(t *testing.T, h HistogramSnapshot) {
 	if count := h.Count(); count != 10000 {
 		t.Errorf("h.Count(): 10000 != %v\n", count)
 	}

metrics/librato/librato.go

@@ -61,7 +61,7 @@ func (rep *Reporter) Run() {
 
 // calculate sum of squares from data provided by metrics.Histogram
 // see http://en.wikipedia.org/wiki/Standard_deviation#Rapid_calculation_methods
-func sumSquares(s metrics.Sample) float64 {
+func sumSquares(s metrics.SampleSnapshot) float64 {
 	count := float64(s.Count())
 	sumSquared := math.Pow(count*s.Mean(), 2)
 	sumSquares := math.Pow(count*s.StdDev(), 2) + sumSquared/count
@@ -70,7 +70,7 @@ func sumSquares(s metrics.Sample) float64 {
 	}
 	return sumSquares
 }
-func sumSquaresTimer(t metrics.Timer) float64 {
+func sumSquaresTimer(t metrics.TimerSnapshot) float64 {
 	count := float64(t.Count())
 	sumSquared := math.Pow(count*t.Mean(), 2)
 	sumSquares := math.Pow(count*t.StdDev(), 2) + sumSquared/count
@@ -97,9 +97,10 @@ func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot B
 		measurement[Period] = rep.Interval.Seconds()
 		switch m := metric.(type) {
 		case metrics.Counter:
+			ms := m.Snapshot()
 			if m.Count() > 0 {
 				measurement[Name] = fmt.Sprintf("%s.%s", name, "count")
-				measurement[Value] = float64(m.Count())
+				measurement[Value] = float64(ms.Count())
 				measurement[Attributes] = map[string]interface{}{
 					DisplayUnitsLong:  Operations,
 					DisplayUnitsShort: OperationsShort,
@@ -108,9 +109,9 @@ func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot B
 				snapshot.Counters = append(snapshot.Counters, measurement)
 			}
 		case metrics.CounterFloat64:
-			if m.Count() > 0 {
+			if count := m.Snapshot().Count(); count > 0 {
 				measurement[Name] = fmt.Sprintf("%s.%s", name, "count")
-				measurement[Value] = m.Count()
+				measurement[Value] = count
 				measurement[Attributes] = map[string]interface{}{
 					DisplayUnitsLong:  Operations,
 					DisplayUnitsShort: OperationsShort,
@@ -120,20 +121,21 @@ func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot B
 			}
 		case metrics.Gauge:
 			measurement[Name] = name
-			measurement[Value] = float64(m.Value())
+			measurement[Value] = float64(m.Snapshot().Value())
 			snapshot.Gauges = append(snapshot.Gauges, measurement)
 		case metrics.GaugeFloat64:
 			measurement[Name] = name
-			measurement[Value] = m.Value()
+			measurement[Value] = m.Snapshot().Value()
 			snapshot.Gauges = append(snapshot.Gauges, measurement)
 		case metrics.GaugeInfo:
 			measurement[Name] = name
 			measurement[Value] = m.Value()
 			snapshot.Gauges = append(snapshot.Gauges, measurement)
 		case metrics.Histogram:
-			if m.Count() > 0 {
+			ms := m.Snapshot()
+			if ms.Count() > 0 {
 				gauges := make([]Measurement, histogramGaugeCount)
-				s := m.Sample()
+				s := ms.Sample()
 				measurement[Name] = fmt.Sprintf("%s.%s", name, "hist")
 				measurement[Count] = uint64(s.Count())
 				measurement[Max] = float64(s.Max())
@@ -151,13 +153,14 @@ func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot B
 				snapshot.Gauges = append(snapshot.Gauges, gauges...)
 			}
 		case metrics.Meter:
+			ms := m.Snapshot()
 			measurement[Name] = name
-			measurement[Value] = float64(m.Count())
+			measurement[Value] = float64(ms.Count())
 			snapshot.Counters = append(snapshot.Counters, measurement)
 			snapshot.Gauges = append(snapshot.Gauges,
 				Measurement{
 					Name:   fmt.Sprintf("%s.%s", name, "1min"),
-					Value:  m.Rate1(),
+					Value:  ms.Rate1(),
 					Period: int64(rep.Interval.Seconds()),
 					Attributes: map[string]interface{}{
 						DisplayUnitsLong:  Operations,
@@ -167,7 +170,7 @@ func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot B
 				},
 				Measurement{
 					Name:   fmt.Sprintf("%s.%s", name, "5min"),
-					Value:  m.Rate5(),
+					Value:  ms.Rate5(),
 					Period: int64(rep.Interval.Seconds()),
 					Attributes: map[string]interface{}{
 						DisplayUnitsLong:  Operations,
@@ -177,7 +180,7 @@ func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot B
 				},
 				Measurement{
 					Name:   fmt.Sprintf("%s.%s", name, "15min"),
-					Value:  m.Rate15(),
+					Value:  ms.Rate15(),
 					Period: int64(rep.Interval.Seconds()),
 					Attributes: map[string]interface{}{
 						DisplayUnitsLong:  Operations,
@@ -187,26 +190,27 @@ func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot B
 				},
 			)
 		case metrics.Timer:
+			ms := m.Snapshot()
 			measurement[Name] = name
-			measurement[Value] = float64(m.Count())
+			measurement[Value] = float64(ms.Count())
 			snapshot.Counters = append(snapshot.Counters, measurement)
-			if m.Count() > 0 {
+			if ms.Count() > 0 {
 				libratoName := fmt.Sprintf("%s.%s", name, "timer.mean")
 				gauges := make([]Measurement, histogramGaugeCount)
 				gauges[0] = Measurement{
 					Name:       libratoName,
-					Count:      uint64(m.Count()),
+					Count:      uint64(ms.Count()),
-					Sum:        m.Mean() * float64(m.Count()),
+					Sum:        ms.Mean() * float64(ms.Count()),
-					Max:        float64(m.Max()),
+					Max:        float64(ms.Max()),
-					Min:        float64(m.Min()),
+					Min:        float64(ms.Min()),
-					SumSquares: sumSquaresTimer(m),
+					SumSquares: sumSquaresTimer(ms),
 					Period:     int64(rep.Interval.Seconds()),
 					Attributes: rep.TimerAttributes,
 				}
 				for i, p := range rep.Percentiles {
 					gauges[i+1] = Measurement{
 						Name:       fmt.Sprintf("%s.timer.%2.0f", name, p*100),
-						Value:      m.Percentile(p),
+						Value:      ms.Percentile(p),
 						Period:     int64(rep.Interval.Seconds()),
 						Attributes: rep.TimerAttributes,
 					}
@@ -215,7 +219,7 @@ func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot B
 				snapshot.Gauges = append(snapshot.Gauges,
 					Measurement{
 						Name:   fmt.Sprintf("%s.%s", name, "rate.1min"),
-						Value:  m.Rate1(),
+						Value:  ms.Rate1(),
 						Period: int64(rep.Interval.Seconds()),
 						Attributes: map[string]interface{}{
 							DisplayUnitsLong:  Operations,
@@ -225,7 +229,7 @@ func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot B
 					},
 					Measurement{
 						Name:   fmt.Sprintf("%s.%s", name, "rate.5min"),
-						Value:  m.Rate5(),
+						Value:  ms.Rate5(),
 						Period: int64(rep.Interval.Seconds()),
 						Attributes: map[string]interface{}{
 							DisplayUnitsLong:  Operations,
@@ -235,7 +239,7 @@ func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot B
 					},
 					Measurement{
 						Name:   fmt.Sprintf("%s.%s", name, "rate.15min"),
-						Value:  m.Rate15(),
+						Value:  ms.Rate15(),
 						Period: int64(rep.Interval.Seconds()),
 						Attributes: map[string]interface{}{
 							DisplayUnitsLong:  Operations,

metrics/log.go

@@ -29,7 +29,7 @@ func LogScaled(r Registry, freq time.Duration, scale time.Duration, l Logger) {
 				l.Printf("  count:       %f\n", metric.Count())
 			case Gauge:
 				l.Printf("gauge %s\n", name)
-				l.Printf("  value:       %9d\n", metric.Value())
+				l.Printf("  value:       %9d\n", metric.Snapshot().Value())
 			case GaugeFloat64:
 				l.Printf("gauge %s\n", name)
 				l.Printf("  value:       %f\n", metric.Value())

metrics/meter.go

@@ -124,7 +124,7 @@ func (NilMeter) Stop() {}
 // StandardMeter is the standard implementation of a Meter.
 type StandardMeter struct {
 	count     atomic.Int64
-	temp     atomic.Int64
+	uncounted atomic.Int64 // not yet added to the EWMAs
 	rateMean  atomic.Uint64
 
 	a1, a5, a15 EWMA
@@ -152,13 +152,13 @@ func (m *StandardMeter) Stop() {
 
 // Mark records the occurrence of n events.
 func (m *StandardMeter) Mark(n int64) {
-	m.temp.Add(n)
+	m.uncounted.Add(n)
 }
 
 // Snapshot returns a read-only copy of the meter.
 func (m *StandardMeter) Snapshot() MeterSnapshot {
 	return &meterSnapshot{
-		count:    m.count.Load(),
+		count:    m.count.Load() + m.uncounted.Load(),
 		rate1:    m.a1.Rate(),
 		rate5:    m.a5.Rate(),
 		rate15:   m.a15.Rate(),
@@ -168,7 +168,7 @@ func (m *StandardMeter) Snapshot() MeterSnapshot {
 
 func (m *StandardMeter) tick() {
 	// Take the uncounted values, add to count
-	n := m.temp.Swap(0)
+	n := m.uncounted.Swap(0)
 	count := m.count.Add(n)
 	m.rateMean.Store(math.Float64bits(float64(count) / time.Since(m.startTime).Seconds()))
 	// Update the EWMA's internal state

metrics/meter_test.go

@@ -12,11 +12,17 @@ func BenchmarkMeter(b *testing.B) {
 		m.Mark(1)
 	}
 }
-
+func TestMeter(t *testing.T) {
+	m := NewMeter()
+	m.Mark(47)
+	if v := m.Snapshot().Count(); v != 47 {
+		t.Fatalf("have %d want %d", v, 47)
+	}
+}
 func TestGetOrRegisterMeter(t *testing.T) {
 	r := NewRegistry()
 	NewRegisteredMeter("foo", r).Mark(47)
-	if m := GetOrRegisterMeter("foo", r); m.Count() != 47 {
+	if m := GetOrRegisterMeter("foo", r).Snapshot(); m.Count() != 47 {
 		t.Fatal(m.Count())
 	}
 }
@@ -31,10 +37,10 @@ func TestMeterDecay(t *testing.T) {
 	ma.meters[m] = struct{}{}
 	m.Mark(1)
 	ma.tickMeters()
-	rateMean := m.RateMean()
+	rateMean := m.Snapshot().RateMean()
 	time.Sleep(100 * time.Millisecond)
 	ma.tickMeters()
-	if m.RateMean() >= rateMean {
+	if m.Snapshot().RateMean() >= rateMean {
 		t.Error("m.RateMean() didn't decrease")
 	}
 }
@@ -42,7 +48,7 @@ func TestMeterDecay(t *testing.T) {
 func TestMeterNonzero(t *testing.T) {
 	m := NewMeter()
 	m.Mark(3)
-	if count := m.Count(); count != 3 {
+	if count := m.Snapshot().Count(); count != 3 {
 		t.Errorf("m.Count(): 3 != %v\n", count)
 	}
 }
@@ -59,16 +65,8 @@ func TestMeterStop(t *testing.T) {
 	}
 }
 
-func TestMeterSnapshot(t *testing.T) {
-	m := NewMeter()
-	m.Mark(1)
-	if snapshot := m.Snapshot(); m.RateMean() != snapshot.RateMean() {
-		t.Fatal(snapshot)
-	}
-}
-
 func TestMeterZero(t *testing.T) {
-	m := NewMeter()
+	m := NewMeter().Snapshot()
 	if count := m.Count(); count != 0 {
 		t.Errorf("m.Count(): 0 != %v\n", count)
 	}
@@ -79,13 +77,13 @@ func TestMeterRepeat(t *testing.T) {
 	for i := 0; i < 101; i++ {
 		m.Mark(int64(i))
 	}
-	if count := m.Count(); count != 5050 {
+	if count := m.Snapshot().Count(); count != 5050 {
 		t.Errorf("m.Count(): 5050 != %v\n", count)
 	}
 	for i := 0; i < 101; i++ {
 		m.Mark(int64(i))
 	}
-	if count := m.Count(); count != 10100 {
+	if count := m.Snapshot().Count(); count != 10100 {
 		t.Errorf("m.Count(): 10100 != %v\n", count)
 	}
 }

metrics/metrics_test.go

@@ -99,7 +99,7 @@ func Example() {
 	t.Update(1)
 
 	fmt.Println(c.Count())
-	fmt.Println(t.Min())
+	fmt.Println(t.Snapshot().Min())
 	// Output: 17
 	// 1
 }

metrics/opentsdb.go

@@ -69,7 +69,7 @@ func (c *OpenTSDBConfig) writeRegistry(w io.Writer, now int64, shortHostname str
 		case CounterFloat64:
 			fmt.Fprintf(w, "put %s.%s.count %d %f host=%s\n", c.Prefix, name, now, metric.Count(), shortHostname)
 		case Gauge:
-			fmt.Fprintf(w, "put %s.%s.value %d %d host=%s\n", c.Prefix, name, now, metric.Value(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.value %d %d host=%s\n", c.Prefix, name, now, metric.Snapshot().Value(), shortHostname)
 		case GaugeFloat64:
 			fmt.Fprintf(w, "put %s.%s.value %d %f host=%s\n", c.Prefix, name, now, metric.Value(), shortHostname)
 		case GaugeInfo:

metrics/prometheus/collector.go

@@ -83,7 +83,7 @@ func (c *collector) addCounterFloat64(name string, m metrics.CounterFloat64) {
 	c.writeGaugeCounter(name, m.Count())
 }
 
-func (c *collector) addGauge(name string, m metrics.Gauge) {
+func (c *collector) addGauge(name string, m metrics.GaugeSnapshot) {
 	c.writeGaugeCounter(name, m.Value())
 }
 

metrics/registry.go

@@ -154,7 +154,7 @@ func (r *StandardRegistry) GetAll() map[string]map[string]interface{} {
 		case CounterFloat64:
 			values["count"] = metric.Count()
 		case Gauge:
-			values["value"] = metric.Value()
+			values["value"] = metric.Snapshot().Value()
 		case GaugeFloat64:
 			values["value"] = metric.Value()
 		case Healthcheck:

metrics/sample.go

@@ -353,8 +353,9 @@ func (s *UniformSample) Snapshot() SampleSnapshot {
 	s.mutex.Lock()
 	values := make([]int64, len(s.values))
 	copy(values, s.values)
+	count := s.count
 	s.mutex.Unlock()
-	return newSampleSnapshot(s.count, s.values)
+	return newSampleSnapshot(count, values)
 }
 
 // Update samples a new value.

metrics/sample_test.go

@@ -87,10 +87,11 @@ func BenchmarkUniformSample1028(b *testing.B) {
 }
 
 func TestExpDecaySample10(t *testing.T) {
-	s := NewExpDecaySample(100, 0.99)
+	sw := NewExpDecaySample(100, 0.99)
 	for i := 0; i < 10; i++ {
-		s.Update(int64(i))
+		sw.Update(int64(i))
 	}
+	s := sw.Snapshot()
 	if size := s.Count(); size != 10 {
 		t.Errorf("s.Count(): 10 != %v\n", size)
 	}
@@ -108,10 +109,11 @@ func TestExpDecaySample10(t *testing.T) {
 }
 
 func TestExpDecaySample100(t *testing.T) {
-	s := NewExpDecaySample(1000, 0.01)
+	sw := NewExpDecaySample(1000, 0.01)
 	for i := 0; i < 100; i++ {
-		s.Update(int64(i))
+		sw.Update(int64(i))
 	}
+	s := sw.Snapshot()
 	if size := s.Count(); size != 100 {
 		t.Errorf("s.Count(): 100 != %v\n", size)
 	}
@@ -129,10 +131,11 @@ func TestExpDecaySample100(t *testing.T) {
 }
 
 func TestExpDecaySample1000(t *testing.T) {
-	s := NewExpDecaySample(100, 0.99)
+	sw := NewExpDecaySample(100, 0.99)
 	for i := 0; i < 1000; i++ {
-		s.Update(int64(i))
+		sw.Update(int64(i))
 	}
+	s := sw.Snapshot()
 	if size := s.Count(); size != 1000 {
 		t.Errorf("s.Count(): 1000 != %v\n", size)
 	}
@@ -154,14 +157,15 @@ func TestExpDecaySample1000(t *testing.T) {
 // The priority becomes +Inf quickly after starting if this is done,
 // effectively freezing the set of samples until a rescale step happens.
 func TestExpDecaySampleNanosecondRegression(t *testing.T) {
-	s := NewExpDecaySample(100, 0.99)
+	sw := NewExpDecaySample(100, 0.99)
 	for i := 0; i < 100; i++ {
-		s.Update(10)
+		sw.Update(10)
 	}
 	time.Sleep(1 * time.Millisecond)
 	for i := 0; i < 100; i++ {
-		s.Update(20)
+		sw.Update(20)
 	}
+	s := sw.Snapshot()
 	v := s.Values()
 	avg := float64(0)
 	for i := 0; i < len(v); i++ {
@@ -201,14 +205,15 @@ func TestExpDecaySampleStatistics(t *testing.T) {
 	for i := 1; i <= 10000; i++ {
 		s.(*ExpDecaySample).update(now.Add(time.Duration(i)), int64(i))
 	}
-	testExpDecaySampleStatistics(t, s)
+	testExpDecaySampleStatistics(t, s.Snapshot())
 }
 
 func TestUniformSample(t *testing.T) {
-	s := NewUniformSample(100)
+	sw := NewUniformSample(100)
 	for i := 0; i < 1000; i++ {
-		s.Update(int64(i))
+		sw.Update(int64(i))
 	}
+	s := sw.Snapshot()
 	if size := s.Count(); size != 1000 {
 		t.Errorf("s.Count(): 1000 != %v\n", size)
 	}
@@ -226,11 +231,12 @@ func TestUniformSample(t *testing.T) {
 }
 
 func TestUniformSampleIncludesTail(t *testing.T) {
-	s := NewUniformSample(100)
+	sw := NewUniformSample(100)
 	max := 100
 	for i := 0; i < max; i++ {
-		s.Update(int64(i))
+		sw.Update(int64(i))
 	}
+	s := sw.Snapshot()
 	v := s.Values()
 	sum := 0
 	exp := (max - 1) * max / 2
@@ -257,7 +263,7 @@ func TestUniformSampleStatistics(t *testing.T) {
 	for i := 1; i <= 10000; i++ {
 		s.Update(int64(i))
 	}
-	testUniformSampleStatistics(t, s)
+	testUniformSampleStatistics(t, s.Snapshot())
 }
 
 func benchmarkSample(b *testing.B, s Sample) {
@@ -274,7 +280,7 @@ func benchmarkSample(b *testing.B, s Sample) {
 	b.Logf("GC cost: %d ns/op", int(memStats.PauseTotalNs-pauseTotalNs)/b.N)
 }
 
-func testExpDecaySampleStatistics(t *testing.T, s Sample) {
+func testExpDecaySampleStatistics(t *testing.T, s SampleSnapshot) {
 	if count := s.Count(); count != 10000 {
 		t.Errorf("s.Count(): 10000 != %v\n", count)
 	}
@@ -302,7 +308,7 @@ func testExpDecaySampleStatistics(t *testing.T, s Sample) {
 	}
 }
 
-func testUniformSampleStatistics(t *testing.T, s Sample) {
+func testUniformSampleStatistics(t *testing.T, s SampleSnapshot) {
 	if count := s.Count(); count != 10000 {
 		t.Errorf("s.Count(): 10000 != %v\n", count)
 	}
@@ -356,7 +362,7 @@ func TestUniformSampleConcurrentUpdateCount(t *testing.T) {
 		}
 	}()
 	for i := 0; i < 1000; i++ {
-		s.Count()
+		s.Snapshot().Count()
 		time.Sleep(5 * time.Millisecond)
 	}
 	quit <- struct{}{}

metrics/syslog.go

@@ -20,7 +20,7 @@ func Syslog(r Registry, d time.Duration, w *syslog.Writer) {
 			case CounterFloat64:
 				w.Info(fmt.Sprintf("counter %s: count: %f", name, metric.Count()))
 			case Gauge:
-				w.Info(fmt.Sprintf("gauge %s: value: %d", name, metric.Value()))
+				w.Info(fmt.Sprintf("gauge %s: value: %d", name, metric.Snapshot().Value()))
 			case GaugeFloat64:
 				w.Info(fmt.Sprintf("gauge %s: value: %f", name, metric.Value()))
 			case GaugeInfo:

metrics/timer_test.go

@@ -18,7 +18,7 @@ func BenchmarkTimer(b *testing.B) {
 func TestGetOrRegisterTimer(t *testing.T) {
 	r := NewRegistry()
 	NewRegisteredTimer("foo", r).Update(47)
-	if tm := GetOrRegisterTimer("foo", r); tm.Count() != 1 {
+	if tm := GetOrRegisterTimer("foo", r).Snapshot(); tm.Count() != 1 {
 		t.Fatal(tm)
 	}
 }
@@ -27,7 +27,7 @@ func TestTimerExtremes(t *testing.T) {
 	tm := NewTimer()
 	tm.Update(math.MaxInt64)
 	tm.Update(0)
-	if stdDev := tm.StdDev(); stdDev != 4.611686018427388e+18 {
+	if stdDev := tm.Snapshot().StdDev(); stdDev != 4.611686018427388e+18 {
 		t.Errorf("tm.StdDev(): 4.611686018427388e+18 != %v\n", stdDev)
 	}
 }
@@ -56,7 +56,7 @@ func TestTimerFunc(t *testing.T) {
 	})
 	var (
 		drift    = time.Millisecond * 2
-		measured = time.Duration(tm.Max())
+		measured = time.Duration(tm.Snapshot().Max())
 		ceil     = actualTime + drift
 		floor    = actualTime - drift
 	)
@@ -66,7 +66,7 @@ func TestTimerFunc(t *testing.T) {
 }
 
 func TestTimerZero(t *testing.T) {
-	tm := NewTimer()
+	tm := NewTimer().Snapshot()
 	if count := tm.Count(); count != 0 {
 		t.Errorf("tm.Count(): 0 != %v\n", count)
 	}
@@ -110,5 +110,5 @@ func ExampleGetOrRegisterTimer() {
 	m := "account.create.latency"
 	t := GetOrRegisterTimer(m, nil)
 	t.Update(47)
-	fmt.Println(t.Max()) // Output: 47
+	fmt.Println(t.Snapshot().Max()) // Output: 47
 }

metrics/writer.go

@@ -35,7 +35,7 @@ func WriteOnce(r Registry, w io.Writer) {
 			fmt.Fprintf(w, "  count:       %f\n", metric.Count())
 		case Gauge:
 			fmt.Fprintf(w, "gauge %s\n", namedMetric.name)
-			fmt.Fprintf(w, "  value:       %9d\n", metric.Value())
+			fmt.Fprintf(w, "  value:       %9d\n", metric.Snapshot().Value())
 		case GaugeFloat64:
 			fmt.Fprintf(w, "gauge %s\n", namedMetric.name)
 			fmt.Fprintf(w, "  value:       %f\n", metric.Value())