Log water mark for incoming queue in cacher

pkg/storage/util_test.go

@@ -16,7 +16,11 @@ limitations under the License.
 
 package storage
 
-import "testing"
+import (
+	"math/rand"
+	"sync"
+	"testing"
+)
 
 func TestEtcdParseWatchResourceVersion(t *testing.T) {
 	testCases := []struct {
@@ -99,3 +103,34 @@ func TestHasPathPrefix(t *testing.T) {
 		}
 	}
 }
+
+func TestHighWaterMark(t *testing.T) {
+	var h HighWaterMark
+
+	for i := int64(10); i < 20; i++ {
+		if !h.Update(i) {
+			t.Errorf("unexpected false for %v", i)
+		}
+		if h.Update(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.Update(v)
+		}(v)
+		if v > m {
+			m = v
+		}
+	}
+	wg.Wait()
+	if m != int64(h) {
+		t.Errorf("unexpected value, wanted %v, got %v", m, int64(h))
+	}
+}