framework/log/FileTarget.php
public function init()
    {
        parent::init();
        if ($this->logFile === null) {
            $this->logFile = Yii::$app->getRuntimePath() . '/logs/app.log';
        } else {
            $this->logFile = Yii::getAlias($this->logFile);
        }
        if ($this->maxLogFiles < 1) {
            $this->maxLogFiles = 1;
        }
        if ($this->maxFileSize < 1) {
            $this->maxFileSize = 1;
        }
    }
public function init()
    {
        parent::init();
        if ($this->logFile === null) {
            $this->logFile = Yii::$app->getRuntimePath() . '/logs/app.log';
        } else {
            $this->logFile = Yii::getAlias($this->logFile);
        }
        if ($this->maxLogFiles < 1) {
            $this->maxLogFiles = 1;
        }
        if ($this->maxFileSize < 1) {
            $this->maxFileSize = 1;
        }
    }
Initializes the route.
This method is invoked after the route is created by the route manager.