KCL: Fix random number generator

Fix the random number generator by adding seed.
https://stackoverflow.com/questions/12321133/golang-random-number-generator-how-to-seed-properly

Jira CNA-1119

Change-Id: Idfe23d84f31a47dcf43c8025632ff6f115614d34

clientlibrary/utils/random.go

@@ -20,6 +20,7 @@ package utils
 
 import (
 	"math/rand"
+	"time"
 )
 
 const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
@@ -31,6 +32,7 @@ const (
 
 func RandStringBytesMaskImpr(n int) string {
 	b := make([]byte, n)
+	rand.Seed(time.Now().UTC().UnixNano())
 	// A rand.Int63() generates 63 random bits, enough for letterIdxMax letters!
 	for i, cache, remain := n-1, rand.Int63(), letterIdxMax; i >= 0; {
 		if remain == 0 {

clientlibrary/utils/random_test.go

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2018 VMware, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+ * associated documentation files (the "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is furnished to do
+ * so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+ * NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package utils
+
+import (
+	"fmt"
+	"math/rand"
+	"testing"
+	"time"
+)
+
+func TestRandom(t *testing.T) {
+	for i := 0; i < 10; i++ {
+		s1 := RandStringBytesMaskImpr(10)
+		s2 := RandStringBytesMaskImpr(10)
+		if s1 == s2 {
+			t.Fatalf("failed in generating random string. s1: %s, s2: %s", s1, s2)
+		}
+	}
+}
+
+func TestRandomNum(t *testing.T) {
+	rand.Seed(time.Now().UTC().UnixNano())
+
+	for i := 0; i < 10; i++ {
+		s1 := rand.Int63()
+		s2 := rand.Int63()
+		if s1 == s2 {
+			t.Fatalf("failed in generating random string. s1: %d, s2: %d", s1, s2)
+		}
+		fmt.Println(s1)
+		fmt.Println(s2)
+	}
+}

clientlibrary/worker/checkpointer.go

@@ -335,10 +335,9 @@ func (checkpointer *DynamoCheckpoint) getItem(shardID string) (map[string]*dynam
 }
 
 func (checkpointer *DynamoCheckpoint) removeItem(shardID string) error {
-	var item *dynamodb.DeleteItemOutput
 	err := try.Do(func(attempt int) (bool, error) {
 		var err error
-		item, err = checkpointer.svc.DeleteItem(&dynamodb.DeleteItemInput{
+		_, err = checkpointer.svc.DeleteItem(&dynamodb.DeleteItemInput{
 			TableName: aws.String(checkpointer.TableName),
 			Key: map[string]*dynamodb.AttributeValue{
 				LEASE_KEY_KEY: {