diff --git a/metrics/meter.go b/metrics/meter.go index 7d2a2f530..60ae919d0 100644 --- a/metrics/meter.go +++ b/metrics/meter.go @@ -101,8 +101,12 @@ func NewRegisteredMeterForced(name string, r Registry) Meter { // MeterSnapshot is a read-only copy of another Meter. type MeterSnapshot struct { - count int64 + // WARNING: The `temp` field is accessed atomically. + // On 32 bit platforms, only 64-bit aligned fields can be atomic. The struct is + // guaranteed to be so aligned, so take advantage of that. For more information, + // see https://golang.org/pkg/sync/atomic/#pkg-note-BUG. temp int64 + count int64 rate1, rate5, rate15, rateMean float64 } @@ -253,7 +257,7 @@ func (m *StandardMeter) updateSnapshot() { func (m *StandardMeter) updateMeter() { // should only run with write lock held on m.lock - n := atomic.LoadInt64(&m.snapshot.temp) + n := atomic.SwapInt64(&m.snapshot.temp, 0) m.snapshot.count += n m.a1.Update(n) m.a5.Update(n) diff --git a/metrics/meter_test.go b/metrics/meter_test.go index 9c43b6156..b3f6cb8c0 100644 --- a/metrics/meter_test.go +++ b/metrics/meter_test.go @@ -73,3 +73,19 @@ func TestMeterZero(t *testing.T) { t.Errorf("m.Count(): 0 != %v\n", count) } } + +func TestMeterRepeat(t *testing.T) { + m := NewMeter() + for i := 0; i < 101; i++ { + m.Mark(int64(i)) + } + if count := m.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 { + t.Errorf("m.Count(): 10100 != %v\n", count) + } +}