yii2-swiftmailer/docs/guide/performance.md

Performance Tuning

Application performance consists of two parts. First is the framework performance and the second is the application itself. Yii has a pretty low performance impact on your application out of the box and can be fine-tuned further for production environment. As for the application, we'll provide some of the best practices along with examples on how to apply them to Yii.

Preparing framework for production

Disabling Debug Mode

First thing you should do before deploying your application to production environment is to disable debug mode. A Yii application runs in debug mode if the constant YII_DEBUG is defined as true in index.php so to disable debug the following should be in your index.php:

defined('YII_DEBUG') or define('YII_DEBUG', false);

Debug mode is very useful during development stage, but it would impact performance because some components cause extra burden in debug mode. For example, the message logger may record additional debug information for every message being logged.

Enabling PHP opcode cache

Enabling the PHP opcode cache improves any PHP application performance and lowers memory usage significantly. Yii is no exception. It was tested with APC PHP extension that caches and optimizes PHP intermediate code and avoids the time spent in parsing PHP scripts for every incoming request.

Turning on ActiveRecord database schema caching

If the application is using Active Record, we should turn on the schema caching to save the time of parsing database schema. This can be done by setting the Connection::enableSchemaCache property to be true via application configuration protected/config/main.php:

return array(
	// ...
	'components' => array(
		// ...
		'db' => array(
			'class' => 'yii\db\Connection',
			'dsn' => 'mysql:host=localhost;dbname=mydatabase',
			'username' => 'root',
			'password' => '',
			'enableSchemaCache' => true,

			// Duration of schema cache.
			// 'schemaCacheDuration' => 3600,

			// Name of the cache component used. Default is 'cache'.
			//'schemaCache' => 'cache',
		),
		'cache' => array(
			'class' => 'yii\caching\FileCache',
		),
	),
);

Note that cache application component should be configured.

Combining and Minimizing Assets

TBD

Using better storage for sessions

By default PHP uses files to handle sessions. It is OK for development and small projects but when it comes to handling concurrent requests it's better to switch to another storage such as database. You can do so by configuring your application via protected/config/main.php:

return array(
	// ...
	'components' => array(
		'session' => array(
			'class' => 'yii\web\DbSession',

			// Set the following if want to use DB component other than
			// default 'db'.
			// 'db' => 'mydb',

			// To override default session table set the following
			// 'sessionTable' => 'my_session',
		),
	),
);

You can use CacheSession to store sessions using cache. Note that some cache storages such as memcached has no guaranteee that session data will not be lost leading to unexpected logouts.

Improving application

Using Serverside Caching Techniques

As described in the Caching section, Yii provides several caching solutions that may improve the performance of a Web application significantly. If the generation of some data takes long time, we can use the data caching approach to reduce the data generation frequency; If a portion of page remains relatively static, we can use the fragment caching approach to reduce its rendering frequency; If a whole page remains relative static, we can use the page caching approach to save the rendering cost for the whole page.

Leveraging HTTP to save procesing time and bandwidth

TBD

Database Optimization

Fetching data from database is often the main performance bottleneck in a Web application. Although using caching may alleviate the performance hit, it does not fully solve the problem. When the database contains enormous data and the cached data is invalid, fetching the latest data could be prohibitively expensive without proper database and query design.

Design index wisely in a database. Indexing can make SELECT queries much faster, but it may slow down INSERT, UPDATE or DELETE queries.

For complex queries, it is recommended to create a database view for it instead of issuing the queries inside the PHP code and asking DBMS to parse them repetitively.

Do not overuse Active Record. Although Active Record is good at modelling data in an OOP fashion, it actually degrades performance due to the fact that it needs to create one or several objects to represent each row of query result. For data intensive applications, using DAO or database APIs at lower level could be a better choice.

Last but not least, use LIMIT in your SELECT queries. This avoids fetching overwhelming data from database and exhausting the memory allocated to PHP.

Using asArray

A good way to save memory and processing time on read-only pages is to use ActiveRecord's asArray method.

class PostController extends Controller
{
	public function actionIndex()
	{
		$posts = Post::find()->orderBy('id DESC')->limit(100)->asArray()->all();
		echo $this->render('index', array(
			'posts' => $posts,
		));
	}
}

In the view you should access fields of each invidual record from $posts as array:

foreach ($posts as $post) {
	echo $post['title']."<br>";
}

Note that you can use array notation even if asArray wasn't specified and you're working with AR objects.

Processing data in background

In order to respond to user requests faster you can process heavy parts of the request later if there's no need for immediate response.

• Cron jobs + console.
• queues + handlers.

TBD