Merge pull request #13755 from ArtfulCoder/shufflestrings

ShuffleStrings uses a seeded rand object

pkg/util/rand/rand.go

@@ -54,3 +54,11 @@ func Seed(seed int64) {
 
 	rng.rand = rand.New(rand.NewSource(seed))
 }
+
+// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n)
+// from the default Source.
+func Perm(n int) []int {
+	rng.Lock()
+	defer rng.Unlock()
+	return rng.rand.Perm(n)
+}

pkg/util/rand/rand_test.go

@@ -17,6 +17,7 @@ limitations under the License.
 package rand
 
 import (
+	"math/rand"
 	"strings"
 	"testing"
 )
@@ -35,3 +36,17 @@ func TestString(t *testing.T) {
 		}
 	}
 }
+
+func TestPerm(t *testing.T) {
+	Seed(5)
+	rand.Seed(5)
+	for i := 1; i < 20; i++ {
+		actual := Perm(i)
+		expected := rand.Perm(i)
+		for j := 0; j < i; j++ {
+			if actual[j] != expected[j] {
+				t.Errorf("Perm call result is unexpected")
+			}
+		}
+	}
+}

pkg/util/slice/slice.go

@@ -18,7 +18,7 @@ limitations under the License.
 package slice
 
 import (
-	"math/rand"
+	utilrand "k8s.io/kubernetes/pkg/util/rand"
 	"sort"
 )
 
@@ -41,7 +41,7 @@ func SortStrings(s []string) []string {
 // order. It returns a new slice.
 func ShuffleStrings(s []string) []string {
 	shuffled := make([]string, len(s))
-	perm := rand.Perm(len(s))
+	perm := utilrand.Perm(len(s))
 	for i, j := range perm {
 		shuffled[j] = s[i]
 	}