Merge pull request #10500 from lavalamp/etcdChanFix

Fix logging.

pkg/util/atomic_value.go

@@ -18,6 +18,7 @@ package util
 
 import (
 	"sync"
+	"sync/atomic"
 )
 
 // TODO(ArtfulCoder)
@@ -40,3 +41,20 @@ func (at *AtomicValue) Load() interface{} {
 	defer at.valueMutex.RUnlock()
 	return at.value
 }
+
+// HighWaterMark is a thread-safe object for tracking the maximum value seen
+// for some quantity.
+type HighWaterMark int64
+
+// Check returns true iff 'current' is the highest value ever seen.
+func (hwm *HighWaterMark) Check(current int64) bool {
+	for {
+		old := atomic.LoadInt64((*int64)(hwm))
+		if current <= old {
+			return false
+		}
+		if atomic.CompareAndSwapInt64((*int64)(hwm), old, current) {
+			return true
+		}
+	}
+}

pkg/util/atomic_value_test.go

@@ -17,6 +17,8 @@ limitations under the License.
 package util
 
 import (
+	"math/rand"
+	"sync"
 	"testing"
 	"time"
 )
@@ -48,3 +50,34 @@ func TestAtomicValue(t *testing.T) {
 	atomicValue.Store(10)
 	ExpectValue(t, atomicValue, 10)
 }
+
+func TestHighWaterMark(t *testing.T) {
+	var h HighWaterMark
+
+	for i := int64(10); i < 20; i++ {
+		if !h.Check(i) {
+			t.Errorf("unexpected false for %v", i)
+		}
+		if h.Check(i - 1) {
+			t.Errorf("unexpected true for %v", i-1)
+		}
+	}
+
+	m := int64(0)
+	wg := sync.WaitGroup{}
+	for i := 0; i < 300; i++ {
+		wg.Add(1)
+		v := rand.Int63()
+		go func(v int64) {
+			defer wg.Done()
+			h.Check(v)
+		}(v)
+		if v > m {
+			m = v
+		}
+	}
+	wg.Wait()
+	if m != int64(h) {
+		t.Errorf("unexpected value, wanted %v, got %v", m, int64(h))
+	}
+}