Refactor rocksmq comments and logs for readability (#15801)

Signed-off-by: yangxuan <xuan.yang@zilliz.com>

internal/util/rocksmq/server/rocksmq/rocksmq_impl.go

@@ -289,17 +289,18 @@ func (rmq *rocksmq) CreateTopic(topicName string) error {
 
 	// Check if topicName contains "/"
 	if strings.Contains(topicName, "/") {
-		log.Error("RocksMQ: create topic failed because topic name contains \"/\"", zap.String("topic", topicName))
+		log.Error("rocksmq failed to create topic for topic name contains \"/\"", zap.String("topic", topicName))
 		return retry.Unrecoverable(fmt.Errorf("topic name = %s contains \"/\"", topicName))
 	}
 
-	// TopicBeginIDTitle is the only identifier of a topic exist or not
+	// topicIDKey is the only identifier of a topic
 	topicIDKey := TopicIDTitle + topicName
 	val, err := rmq.kv.Load(topicIDKey)
 	if err != nil {
 		return err
 	}
 	if val != "" {
+		log.Debug("rocksmq topic already exists ", zap.String("topic", topicName))
 		return nil
 	}
 
@@ -307,19 +308,17 @@ func (rmq *rocksmq) CreateTopic(topicName string) error {
 		topicMu.Store(topicName, new(sync.Mutex))
 	}
 
+	// msgSizeKey -> msgSize
+	// topicIDKey -> topic creating time
 	kvs := make(map[string]string)
+
 	// Initialize topic message size to 0
 	msgSizeKey := MessageSizeTitle + topicName
 	kvs[msgSizeKey] = "0"
 
-	// Initialize topic id to its create Tme, we don't really use it for now
+	// Initialize topic id to its creating time, we don't really use it for now
 	nowTs := strconv.FormatInt(time.Now().Unix(), 10)
 	kvs[topicIDKey] = nowTs
-	err = rmq.kv.Save(topicIDKey, nowTs)
-	if err != nil {
-		return err
-	}
-
 	rmq.kv.MultiSave(kvs)
 
 	rmq.retentionInfo.mutex.Lock()
@@ -329,7 +328,7 @@ func (rmq *rocksmq) CreateTopic(topicName string) error {
 	return nil
 }
 
-// DestroyTopic removes messages for topic in rocksdb
+// DestroyTopic removes messages for topic in rocksmq
 func (rmq *rocksmq) DestroyTopic(topicName string) error {
 	start := time.Now()
 	ll, ok := topicMu.Load(topicName)