src/Session.php
public function init()
    {
        if (is_string($this->redis)) {
            $this->redis = Yii::$app->get($this->redis);
        } elseif (is_array($this->redis)) {
            if (!isset($this->redis['class'])) {
                $this->redis['class'] = Connection::className();
            }
            $this->redis = Yii::createObject($this->redis);
        }
        if (!$this->redis instanceof Connection) {
            throw new InvalidConfigException("Session::redis must be either a Redis connection instance or the application component ID of a Redis connection.");
        }
        if ($this->keyPrefix === null) {
            $this->keyPrefix = substr(md5(Yii::$app->id), 0, 5);
        }
        parent::init();
    }
public function init()
    {
        if (is_string($this->redis)) {
            $this->redis = Yii::$app->get($this->redis);
        } elseif (is_array($this->redis)) {
            if (!isset($this->redis['class'])) {
                $this->redis['class'] = Connection::className();
            }
            $this->redis = Yii::createObject($this->redis);
        }
        if (!$this->redis instanceof Connection) {
            throw new InvalidConfigException("Session::redis must be either a Redis connection instance or the application component ID of a Redis connection.");
        }
        if ($this->keyPrefix === null) {
            $this->keyPrefix = substr(md5(Yii::$app->id), 0, 5);
        }
        parent::init();
    }
Initializes the redis Session component.
This method will initialize the [[redis]] property to make sure it refers to a valid redis connection.
@throws InvalidConfigException if [[redis]] is invalid.