metrics: reduce allocations for metrics (#33699)

metrics/counter.go

@@ -7,7 +7,10 @@ import (
 // GetOrRegisterCounter returns an existing Counter or constructs and registers
 // a new Counter.
 func GetOrRegisterCounter(name string, r Registry) *Counter {
-	return getOrRegister(name, NewCounter, r)
+	if r == nil {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return NewCounter() }).(*Counter)
 }
 
 // NewCounter constructs a new Counter.

metrics/counter_float64.go

@@ -8,7 +8,10 @@ import (
 // GetOrRegisterCounterFloat64 returns an existing *CounterFloat64 or constructs and registers
 // a new CounterFloat64.
 func GetOrRegisterCounterFloat64(name string, r Registry) *CounterFloat64 {
-	return getOrRegister(name, NewCounterFloat64, r)
+	if r == nil {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return NewCounterFloat64() }).(*CounterFloat64)
 }
 
 // NewCounterFloat64 constructs a new CounterFloat64.

metrics/gauge.go

@@ -11,7 +11,10 @@ func (g GaugeSnapshot) Value() int64 { return int64(g) }
 // GetOrRegisterGauge returns an existing Gauge or constructs and registers a
 // new Gauge.
 func GetOrRegisterGauge(name string, r Registry) *Gauge {
-	return getOrRegister(name, NewGauge, r)
+	if r == nil {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return NewGauge() }).(*Gauge)
 }
 
 // NewGauge constructs a new Gauge.

metrics/gauge_float64.go

@@ -8,7 +8,10 @@ import (
 // GetOrRegisterGaugeFloat64 returns an existing GaugeFloat64 or constructs and registers a
 // new GaugeFloat64.
 func GetOrRegisterGaugeFloat64(name string, r Registry) *GaugeFloat64 {
-	return getOrRegister(name, NewGaugeFloat64, r)
+	if r == nil {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return NewGaugeFloat64() }).(*GaugeFloat64)
 }
 
 // GaugeFloat64Snapshot is a read-only copy of a GaugeFloat64.

metrics/gauge_info.go

@@ -16,7 +16,10 @@ func (val GaugeInfoValue) String() string {
 // GetOrRegisterGaugeInfo returns an existing GaugeInfo or constructs and registers a
 // new GaugeInfo.
 func GetOrRegisterGaugeInfo(name string, r Registry) *GaugeInfo {
-	return getOrRegister(name, NewGaugeInfo, r)
+	if r == nil {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return NewGaugeInfo() }).(*GaugeInfo)
 }
 
 // NewGaugeInfo constructs a new GaugeInfo.

metrics/histogram.go

@@ -23,13 +23,19 @@ type Histogram interface {
 // GetOrRegisterHistogram returns an existing Histogram or constructs and
 // registers a new StandardHistogram.
 func GetOrRegisterHistogram(name string, r Registry, s Sample) Histogram {
-	return getOrRegister(name, func() Histogram { return NewHistogram(s) }, r)
+	if r == nil {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return NewHistogram(s) }).(Histogram)
 }
 
 // GetOrRegisterHistogramLazy returns an existing Histogram or constructs and
 // registers a new StandardHistogram.
 func GetOrRegisterHistogramLazy(name string, r Registry, s func() Sample) Histogram {
-	return getOrRegister(name, func() Histogram { return NewHistogram(s()) }, r)
+	if r == nil {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return NewHistogram(s()) }).(Histogram)
 }
 
 // NewHistogram constructs a new StandardHistogram from a Sample.

metrics/meter.go

@@ -12,7 +12,10 @@ import (
 // Be sure to unregister the meter from the registry once it is of no use to
 // allow for garbage collection.
 func GetOrRegisterMeter(name string, r Registry) *Meter {
-	return getOrRegister(name, NewMeter, r)
+	if r == nil {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return NewMeter() }).(*Meter)
 }
 
 // NewMeter constructs a new Meter and launches a goroutine.

metrics/registry.go

@@ -345,13 +345,6 @@ func GetOrRegister(name string, i func() interface{}) interface{} {
 	return DefaultRegistry.GetOrRegister(name, i)
 }
 
-func getOrRegister[T any](name string, ctor func() T, r Registry) T {
-	if r == nil {
-		r = DefaultRegistry
-	}
-	return r.GetOrRegister(name, func() any { return ctor() }).(T)
-}
-
 // Register the given metric under the given name.  Returns a ErrDuplicateMetric
 // if a metric by the given name is already registered.
 func Register(name string, i interface{}) error {

metrics/registry_test.go

@@ -14,6 +14,31 @@ func BenchmarkRegistry(b *testing.B) {
 	}
 }
 
+func BenchmarkRegistryGetOrRegister(b *testing.B) {
+	sample := func() Sample { return nil }
+	tests := []struct {
+		name string
+		ctor func() any
+	}{
+		{name: "counter", ctor: func() any { return GetOrRegisterCounter("counter", DefaultRegistry) }},
+		{name: "gauge", ctor: func() any { return GetOrRegisterGauge("gauge", DefaultRegistry) }},
+		{name: "gaugefloat64", ctor: func() any { return GetOrRegisterGaugeFloat64("gaugefloat64", DefaultRegistry) }},
+		{name: "histogram", ctor: func() any { return GetOrRegisterHistogram("histogram", DefaultRegistry, sample()) }},
+		{name: "meter", ctor: func() any { return GetOrRegisterMeter("meter", DefaultRegistry) }},
+		{name: "timer", ctor: func() any { return GetOrRegisterTimer("timer", DefaultRegistry) }},
+		{name: "gaugeinfo", ctor: func() any { return GetOrRegisterGaugeInfo("gaugeinfo", DefaultRegistry) }},
+		{name: "resettingtimer", ctor: func() any { return GetOrRegisterResettingTimer("resettingtimer", DefaultRegistry) }},
+		{name: "runtimehistogramlazy", ctor: func() any { return GetOrRegisterHistogramLazy("runtimehistogramlazy", DefaultRegistry, sample) }},
+	}
+	for _, test := range tests {
+		b.Run(test.name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				test.ctor()
+			}
+		})
+	}
+}
+
 func BenchmarkRegistryGetOrRegisterParallel_8(b *testing.B) {
 	benchmarkRegistryGetOrRegisterParallel(b, 8)
 }
@@ -268,7 +293,7 @@ func TestPrefixedChildRegistryGet(t *testing.T) {
 }
 
 func TestChildPrefixedRegistryRegister(t *testing.T) {
-	r := NewPrefixedChildRegistry(DefaultRegistry, "prefix.")
+	r := NewPrefixedChildRegistry(NewRegistry(), "prefix.")
 	err := r.Register("foo", NewCounter())
 	c := NewCounter()
 	Register("bar", c)

metrics/resetting_timer.go

@@ -8,7 +8,10 @@ import (
 // GetOrRegisterResettingTimer returns an existing ResettingTimer or constructs and registers a
 // new ResettingTimer.
 func GetOrRegisterResettingTimer(name string, r Registry) *ResettingTimer {
-	return getOrRegister(name, NewResettingTimer, r)
+	if r == nil {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return NewResettingTimer() }).(*ResettingTimer)
 }
 
 // NewRegisteredResettingTimer constructs and registers a new ResettingTimer.

metrics/runtimehistogram.go

@@ -8,8 +8,10 @@ import (
 )
 
 func getOrRegisterRuntimeHistogram(name string, scale float64, r Registry) *runtimeHistogram {
-	constructor := func() Histogram { return newRuntimeHistogram(scale) }
+	if r == nil {
-	return getOrRegister(name, constructor, r).(*runtimeHistogram)
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return newRuntimeHistogram(scale) }).(*runtimeHistogram)
 }
 
 // runtimeHistogram wraps a runtime/metrics histogram.

metrics/timer.go

@@ -10,7 +10,10 @@ import (
 // Be sure to unregister the meter from the registry once it is of no use to
 // allow for garbage collection.
 func GetOrRegisterTimer(name string, r Registry) *Timer {
-	return getOrRegister(name, NewTimer, r)
+	if r == nil {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() any { return NewTimer() }).(*Timer)
 }
 
 // NewCustomTimer constructs a new Timer from a Histogram and a Meter.