Fixed #252 - guard against multiple registrations of runtime and debug stats

debug.go

@@ -3,6 +3,7 @@ package metrics
 import (
 	"runtime/debug"
 	"time"
+	"sync"
 )
 
 var (
@@ -16,7 +17,8 @@ var (
 		}
 		ReadGCStats Timer
 	}
-	gcStats debug.GCStats
+	gcStats                  debug.GCStats
+	registerDebugMetricsOnce = sync.Once{}
 )
 
 // Capture new values for the Go garbage collector statistics exported in
@@ -54,19 +56,21 @@ func CaptureDebugGCStatsOnce(r Registry) {
 // debug.GCStats.  The metrics are named by their fully-qualified Go symbols,
 // i.e. debug.GCStats.PauseTotal.
 func RegisterDebugGCStats(r Registry) {
-	debugMetrics.GCStats.LastGC = NewGauge()
-	debugMetrics.GCStats.NumGC = NewGauge()
-	debugMetrics.GCStats.Pause = NewHistogram(NewExpDecaySample(1028, 0.015))
-	//debugMetrics.GCStats.PauseQuantiles = NewHistogram(NewExpDecaySample(1028, 0.015))
-	debugMetrics.GCStats.PauseTotal = NewGauge()
-	debugMetrics.ReadGCStats = NewTimer()
+	registerDebugMetricsOnce.Do(func() {
+		debugMetrics.GCStats.LastGC = NewGauge()
+		debugMetrics.GCStats.NumGC = NewGauge()
+		debugMetrics.GCStats.Pause = NewHistogram(NewExpDecaySample(1028, 0.015))
+		//debugMetrics.GCStats.PauseQuantiles = NewHistogram(NewExpDecaySample(1028, 0.015))
+		debugMetrics.GCStats.PauseTotal = NewGauge()
+		debugMetrics.ReadGCStats = NewTimer()
 
-	r.Register("debug.GCStats.LastGC", debugMetrics.GCStats.LastGC)
-	r.Register("debug.GCStats.NumGC", debugMetrics.GCStats.NumGC)
-	r.Register("debug.GCStats.Pause", debugMetrics.GCStats.Pause)
-	//r.Register("debug.GCStats.PauseQuantiles", debugMetrics.GCStats.PauseQuantiles)
-	r.Register("debug.GCStats.PauseTotal", debugMetrics.GCStats.PauseTotal)
-	r.Register("debug.ReadGCStats", debugMetrics.ReadGCStats)
+		r.Register("debug.GCStats.LastGC", debugMetrics.GCStats.LastGC)
+		r.Register("debug.GCStats.NumGC", debugMetrics.GCStats.NumGC)
+		r.Register("debug.GCStats.Pause", debugMetrics.GCStats.Pause)
+		//r.Register("debug.GCStats.PauseQuantiles", debugMetrics.GCStats.PauseQuantiles)
+		r.Register("debug.GCStats.PauseTotal", debugMetrics.GCStats.PauseTotal)
+		r.Register("debug.ReadGCStats", debugMetrics.ReadGCStats)
+	})
 }
 
 // Allocate an initial slice for gcStats.Pause to avoid allocations during

debug_test.go

@@ -46,3 +46,19 @@ func testDebugGCStatsBlocking(ch chan int) {
 		}
 	}
 }
+
+func TestDebugGCStatsDoubleRegister(t *testing.T) {
+	r := NewRegistry()
+	RegisterDebugGCStats(r)
+	zero := debugMetrics.GCStats.NumGC.Value() // Get a "zero" since GC may have run before these tests.
+	runtime.GC()
+	CaptureDebugGCStatsOnce(r)
+	if numGC := debugMetrics.GCStats.NumGC.Value(); 1 != numGC - zero {
+		t.Errorf("NumGC got %d, expected 1", numGC)
+	}
+
+	RegisterDebugGCStats(r)
+	if numGC := debugMetrics.GCStats.NumGC.Value(); 1 != numGC - zero {
+		t.Errorf("NumGC got %d, expected 1", numGC - zero)
+	}
+}

runtime.go

@@ -4,6 +4,7 @@ import (
 	"runtime"
 	"runtime/pprof"
 	"time"
+	"sync"
 )
 
 var (
@@ -50,6 +51,7 @@ var (
 	numCgoCalls int64
 
 	threadCreateProfile = pprof.Lookup("threadcreate")
+	registerRuntimeMetricsOnce = sync.Once{}
 )
 
 // Capture new values for the Go runtime statistics exported in
@@ -146,67 +148,69 @@ func CaptureRuntimeMemStatsOnce(r Registry) {
 // specifically runtime.MemStats.  The runtimeMetrics are named by their
 // fully-qualified Go symbols, i.e. runtime.MemStats.Alloc.
 func RegisterRuntimeMemStats(r Registry) {
-	runtimeMetrics.MemStats.Alloc = NewGauge()
-	runtimeMetrics.MemStats.BuckHashSys = NewGauge()
-	runtimeMetrics.MemStats.DebugGC = NewGauge()
-	runtimeMetrics.MemStats.EnableGC = NewGauge()
-	runtimeMetrics.MemStats.Frees = NewGauge()
-	runtimeMetrics.MemStats.HeapAlloc = NewGauge()
-	runtimeMetrics.MemStats.HeapIdle = NewGauge()
-	runtimeMetrics.MemStats.HeapInuse = NewGauge()
-	runtimeMetrics.MemStats.HeapObjects = NewGauge()
-	runtimeMetrics.MemStats.HeapReleased = NewGauge()
-	runtimeMetrics.MemStats.HeapSys = NewGauge()
-	runtimeMetrics.MemStats.LastGC = NewGauge()
-	runtimeMetrics.MemStats.Lookups = NewGauge()
-	runtimeMetrics.MemStats.Mallocs = NewGauge()
-	runtimeMetrics.MemStats.MCacheInuse = NewGauge()
-	runtimeMetrics.MemStats.MCacheSys = NewGauge()
-	runtimeMetrics.MemStats.MSpanInuse = NewGauge()
-	runtimeMetrics.MemStats.MSpanSys = NewGauge()
-	runtimeMetrics.MemStats.NextGC = NewGauge()
-	runtimeMetrics.MemStats.NumGC = NewGauge()
-	runtimeMetrics.MemStats.GCCPUFraction = NewGaugeFloat64()
-	runtimeMetrics.MemStats.PauseNs = NewHistogram(NewExpDecaySample(1028, 0.015))
-	runtimeMetrics.MemStats.PauseTotalNs = NewGauge()
-	runtimeMetrics.MemStats.StackInuse = NewGauge()
-	runtimeMetrics.MemStats.StackSys = NewGauge()
-	runtimeMetrics.MemStats.Sys = NewGauge()
-	runtimeMetrics.MemStats.TotalAlloc = NewGauge()
-	runtimeMetrics.NumCgoCall = NewGauge()
-	runtimeMetrics.NumGoroutine = NewGauge()
-	runtimeMetrics.NumThread = NewGauge()
-	runtimeMetrics.ReadMemStats = NewTimer()
+	registerRuntimeMetricsOnce.Do(func() {
+		runtimeMetrics.MemStats.Alloc = NewGauge()
+		runtimeMetrics.MemStats.BuckHashSys = NewGauge()
+		runtimeMetrics.MemStats.DebugGC = NewGauge()
+		runtimeMetrics.MemStats.EnableGC = NewGauge()
+		runtimeMetrics.MemStats.Frees = NewGauge()
+		runtimeMetrics.MemStats.HeapAlloc = NewGauge()
+		runtimeMetrics.MemStats.HeapIdle = NewGauge()
+		runtimeMetrics.MemStats.HeapInuse = NewGauge()
+		runtimeMetrics.MemStats.HeapObjects = NewGauge()
+		runtimeMetrics.MemStats.HeapReleased = NewGauge()
+		runtimeMetrics.MemStats.HeapSys = NewGauge()
+		runtimeMetrics.MemStats.LastGC = NewGauge()
+		runtimeMetrics.MemStats.Lookups = NewGauge()
+		runtimeMetrics.MemStats.Mallocs = NewGauge()
+		runtimeMetrics.MemStats.MCacheInuse = NewGauge()
+		runtimeMetrics.MemStats.MCacheSys = NewGauge()
+		runtimeMetrics.MemStats.MSpanInuse = NewGauge()
+		runtimeMetrics.MemStats.MSpanSys = NewGauge()
+		runtimeMetrics.MemStats.NextGC = NewGauge()
+		runtimeMetrics.MemStats.NumGC = NewGauge()
+		runtimeMetrics.MemStats.GCCPUFraction = NewGaugeFloat64()
+		runtimeMetrics.MemStats.PauseNs = NewHistogram(NewExpDecaySample(1028, 0.015))
+		runtimeMetrics.MemStats.PauseTotalNs = NewGauge()
+		runtimeMetrics.MemStats.StackInuse = NewGauge()
+		runtimeMetrics.MemStats.StackSys = NewGauge()
+		runtimeMetrics.MemStats.Sys = NewGauge()
+		runtimeMetrics.MemStats.TotalAlloc = NewGauge()
+		runtimeMetrics.NumCgoCall = NewGauge()
+		runtimeMetrics.NumGoroutine = NewGauge()
+		runtimeMetrics.NumThread = NewGauge()
+		runtimeMetrics.ReadMemStats = NewTimer()
 
-	r.Register("runtime.MemStats.Alloc", runtimeMetrics.MemStats.Alloc)
-	r.Register("runtime.MemStats.BuckHashSys", runtimeMetrics.MemStats.BuckHashSys)
-	r.Register("runtime.MemStats.DebugGC", runtimeMetrics.MemStats.DebugGC)
-	r.Register("runtime.MemStats.EnableGC", runtimeMetrics.MemStats.EnableGC)
-	r.Register("runtime.MemStats.Frees", runtimeMetrics.MemStats.Frees)
-	r.Register("runtime.MemStats.HeapAlloc", runtimeMetrics.MemStats.HeapAlloc)
-	r.Register("runtime.MemStats.HeapIdle", runtimeMetrics.MemStats.HeapIdle)
-	r.Register("runtime.MemStats.HeapInuse", runtimeMetrics.MemStats.HeapInuse)
-	r.Register("runtime.MemStats.HeapObjects", runtimeMetrics.MemStats.HeapObjects)
-	r.Register("runtime.MemStats.HeapReleased", runtimeMetrics.MemStats.HeapReleased)
-	r.Register("runtime.MemStats.HeapSys", runtimeMetrics.MemStats.HeapSys)
-	r.Register("runtime.MemStats.LastGC", runtimeMetrics.MemStats.LastGC)
-	r.Register("runtime.MemStats.Lookups", runtimeMetrics.MemStats.Lookups)
-	r.Register("runtime.MemStats.Mallocs", runtimeMetrics.MemStats.Mallocs)
-	r.Register("runtime.MemStats.MCacheInuse", runtimeMetrics.MemStats.MCacheInuse)
-	r.Register("runtime.MemStats.MCacheSys", runtimeMetrics.MemStats.MCacheSys)
-	r.Register("runtime.MemStats.MSpanInuse", runtimeMetrics.MemStats.MSpanInuse)
-	r.Register("runtime.MemStats.MSpanSys", runtimeMetrics.MemStats.MSpanSys)
-	r.Register("runtime.MemStats.NextGC", runtimeMetrics.MemStats.NextGC)
-	r.Register("runtime.MemStats.NumGC", runtimeMetrics.MemStats.NumGC)
-	r.Register("runtime.MemStats.GCCPUFraction", runtimeMetrics.MemStats.GCCPUFraction)
-	r.Register("runtime.MemStats.PauseNs", runtimeMetrics.MemStats.PauseNs)
-	r.Register("runtime.MemStats.PauseTotalNs", runtimeMetrics.MemStats.PauseTotalNs)
-	r.Register("runtime.MemStats.StackInuse", runtimeMetrics.MemStats.StackInuse)
-	r.Register("runtime.MemStats.StackSys", runtimeMetrics.MemStats.StackSys)
-	r.Register("runtime.MemStats.Sys", runtimeMetrics.MemStats.Sys)
-	r.Register("runtime.MemStats.TotalAlloc", runtimeMetrics.MemStats.TotalAlloc)
-	r.Register("runtime.NumCgoCall", runtimeMetrics.NumCgoCall)
-	r.Register("runtime.NumGoroutine", runtimeMetrics.NumGoroutine)
-	r.Register("runtime.NumThread", runtimeMetrics.NumThread)
-	r.Register("runtime.ReadMemStats", runtimeMetrics.ReadMemStats)
+		r.Register("runtime.MemStats.Alloc", runtimeMetrics.MemStats.Alloc)
+		r.Register("runtime.MemStats.BuckHashSys", runtimeMetrics.MemStats.BuckHashSys)
+		r.Register("runtime.MemStats.DebugGC", runtimeMetrics.MemStats.DebugGC)
+		r.Register("runtime.MemStats.EnableGC", runtimeMetrics.MemStats.EnableGC)
+		r.Register("runtime.MemStats.Frees", runtimeMetrics.MemStats.Frees)
+		r.Register("runtime.MemStats.HeapAlloc", runtimeMetrics.MemStats.HeapAlloc)
+		r.Register("runtime.MemStats.HeapIdle", runtimeMetrics.MemStats.HeapIdle)
+		r.Register("runtime.MemStats.HeapInuse", runtimeMetrics.MemStats.HeapInuse)
+		r.Register("runtime.MemStats.HeapObjects", runtimeMetrics.MemStats.HeapObjects)
+		r.Register("runtime.MemStats.HeapReleased", runtimeMetrics.MemStats.HeapReleased)
+		r.Register("runtime.MemStats.HeapSys", runtimeMetrics.MemStats.HeapSys)
+		r.Register("runtime.MemStats.LastGC", runtimeMetrics.MemStats.LastGC)
+		r.Register("runtime.MemStats.Lookups", runtimeMetrics.MemStats.Lookups)
+		r.Register("runtime.MemStats.Mallocs", runtimeMetrics.MemStats.Mallocs)
+		r.Register("runtime.MemStats.MCacheInuse", runtimeMetrics.MemStats.MCacheInuse)
+		r.Register("runtime.MemStats.MCacheSys", runtimeMetrics.MemStats.MCacheSys)
+		r.Register("runtime.MemStats.MSpanInuse", runtimeMetrics.MemStats.MSpanInuse)
+		r.Register("runtime.MemStats.MSpanSys", runtimeMetrics.MemStats.MSpanSys)
+		r.Register("runtime.MemStats.NextGC", runtimeMetrics.MemStats.NextGC)
+		r.Register("runtime.MemStats.NumGC", runtimeMetrics.MemStats.NumGC)
+		r.Register("runtime.MemStats.GCCPUFraction", runtimeMetrics.MemStats.GCCPUFraction)
+		r.Register("runtime.MemStats.PauseNs", runtimeMetrics.MemStats.PauseNs)
+		r.Register("runtime.MemStats.PauseTotalNs", runtimeMetrics.MemStats.PauseTotalNs)
+		r.Register("runtime.MemStats.StackInuse", runtimeMetrics.MemStats.StackInuse)
+		r.Register("runtime.MemStats.StackSys", runtimeMetrics.MemStats.StackSys)
+		r.Register("runtime.MemStats.Sys", runtimeMetrics.MemStats.Sys)
+		r.Register("runtime.MemStats.TotalAlloc", runtimeMetrics.MemStats.TotalAlloc)
+		r.Register("runtime.NumCgoCall", runtimeMetrics.NumCgoCall)
+		r.Register("runtime.NumGoroutine", runtimeMetrics.NumGoroutine)
+		r.Register("runtime.NumThread", runtimeMetrics.NumThread)
+		r.Register("runtime.ReadMemStats", runtimeMetrics.ReadMemStats)
+	})
 }

runtime_test.go

@@ -86,3 +86,20 @@ func testRuntimeMemStatsBlocking(ch chan int) {
 		}
 	}
 }
+
+func TestRuntimeMemStatsDoubleRegister(t *testing.T) {
+	r := NewRegistry()
+	RegisterRuntimeMemStats(r)
+	zero := runtimeMetrics.MemStats.NumGC.Value() // Get a "zero" since GC may have run before these tests.
+	runtime.GC()
+	CaptureRuntimeMemStatsOnce(r)
+
+	if count := runtimeMetrics.MemStats.NumGC.Value(); 1 != count - zero {
+		t.Errorf("NumGC got %d, expected 1", count - zero)
+	}
+
+	RegisterRuntimeMemStats(r)
+	if count := runtimeMetrics.MemStats.NumGC.Value(); 1 != count - zero {
+		t.Errorf("NumGC got %d, expected 1", count - zero)
+	}
+}