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					Performance Tuning | 
				
			
			
		
	
		
		
			
				
					
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					================== | 
				
			
			
		
	
		
		
			
				
					
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					Application performance consists of two parts. First is the framework performance | 
				
			
			
		
	
		
		
			
				
					
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					and the second is the application itself. Yii has a pretty low performance impact | 
				
			
			
		
	
		
		
			
				
					
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					on your application out of the box and can be fine-tuned further for production | 
				
			
			
		
	
		
		
			
				
					
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					environment. As for the application, we'll provide some of the best practices | 
				
			
			
		
	
		
		
			
				
					
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					along with examples on how to apply them to Yii. | 
				
			
			
		
	
		
		
			
				
					
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					Preparing framework for production | 
				
			
			
		
	
		
		
			
				
					
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					---------------------------------- | 
				
			
			
		
	
		
		
			
				
					
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					### Disabling Debug Mode | 
				
			
			
		
	
		
		
			
				
					
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					First thing you should do before deploying your application to production environment | 
				
			
			
		
	
		
		
			
				
					
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					is to disable debug mode. A Yii application runs in debug mode if the constant | 
				
			
			
		
	
		
		
			
				
					
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					`YII_DEBUG` is defined as `true` in `index.php` so to disable debug the following | 
				
			
			
		
	
		
		
			
				
					
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					should be in your `index.php`: | 
				
			
			
		
	
		
		
			
				
					
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					```php | 
				
			
			
		
	
		
		
			
				
					
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					defined('YII_DEBUG') or define('YII_DEBUG', false); | 
				
			
			
		
	
		
		
			
				
					
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					``` | 
				
			
			
		
	
		
		
			
				
					
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					Debug mode is very useful during development stage, but it would impact performance | 
				
			
			
		
	
		
		
			
				
					
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					because some components cause extra burden in debug mode. For example, the message | 
				
			
			
		
	
		
		
			
				
					
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					logger may record additional debug information for every message being logged. | 
				
			
			
		
	
		
		
			
				
					
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					### Enabling PHP opcode cache | 
				
			
			
		
	
		
		
			
				
					
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					Enabling the PHP opcode cache improves any PHP application performance and lowers | 
				
			
			
		
	
		
		
			
				
					
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					memory usage significantly. Yii is no exception. It was tested with | 
				
			
			
		
	
		
		
			
				
					
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					[APC PHP extension](http://php.net/manual/en/book.apc.php) that caches | 
				
			
			
		
	
		
		
			
				
					
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					and optimizes PHP intermediate code and avoids the time spent in parsing PHP | 
				
			
			
		
	
		
		
			
				
					
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					scripts for every incoming request. | 
				
			
			
		
	
		
		
			
				
					
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					### Turning on ActiveRecord database schema caching | 
				
			
			
		
	
		
		
			
				
					
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					If the application is using Active Record, we should turn on the schema caching | 
				
			
			
		
	
		
		
			
				
					
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					to save the time of parsing database schema. This can be done by setting the | 
				
			
			
		
	
		
		
			
				
					
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					`Connection::enableSchemaCache` property to be `true` via application configuration | 
				
			
			
		
	
		
		
			
				
					
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					`protected/config/main.php`: | 
				
			
			
		
	
		
		
			
				
					
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					```php | 
				
			
			
		
	
		
		
			
				
					
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					return array( | 
				
			
			
		
	
		
		
			
				
					
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						// ... | 
				
			
			
		
	
		
		
			
				
					
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						'components' => array( | 
				
			
			
		
	
		
		
			
				
					
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							// ... | 
				
			
			
		
	
		
		
			
				
					
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							'db' => array( | 
				
			
			
		
	
		
		
			
				
					
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								'class' => 'yii\db\Connection', | 
				
			
			
		
	
		
		
			
				
					
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								'dsn' => 'mysql:host=localhost;dbname=mydatabase', | 
				
			
			
		
	
		
		
			
				
					
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								'username' => 'root', | 
				
			
			
		
	
		
		
			
				
					
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								'password' => '', | 
				
			
			
		
	
		
		
			
				
					
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								'enableSchemaCache' => true, | 
				
			
			
		
	
		
		
			
				
					
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								// Duration of schema cache. | 
				
			
			
		
	
		
		
			
				
					
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								// 'schemaCacheDuration' => 3600, | 
				
			
			
		
	
		
		
			
				
					
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								// Name of the cache component used. Default is 'cache'. | 
				
			
			
		
	
		
		
			
				
					
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								//'schemaCache' => 'cache', | 
				
			
			
		
	
		
		
			
				
					
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							), | 
				
			
			
		
	
		
		
			
				
					
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							'cache' => array( | 
				
			
			
		
	
		
		
			
				
					
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								'class' => 'yii\caching\FileCache', | 
				
			
			
		
	
		
		
			
				
					
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							), | 
				
			
			
		
	
		
		
			
				
					
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						), | 
				
			
			
		
	
		
		
			
				
					
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					); | 
				
			
			
		
	
		
		
			
				
					
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					``` | 
				
			
			
		
	
		
		
			
				
					
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					Note that `cache` application component should be configured. | 
				
			
			
		
	
		
		
			
				
					
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					### Combining and Minimizing Assets | 
				
			
			
		
	
		
		
			
				
					
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					TBD | 
				
			
			
		
	
		
		
			
				
					
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					### Using better storage for sessions | 
				
			
			
		
	
		
		
			
				
					
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					By default PHP uses files to handle sessions. It is OK for development and | 
				
			
			
		
	
		
		
			
				
					
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					small projects but when it comes to handling concurrent requests it's better to | 
				
			
			
		
	
		
		
			
				
					
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					switch to another storage such as database. You can do so by configuring your | 
				
			
			
		
	
		
		
			
				
					
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					application via `protected/config/main.php`: | 
				
			
			
		
	
		
		
			
				
					
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					```php | 
				
			
			
		
	
		
		
			
				
					
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					return array( | 
				
			
			
		
	
		
		
			
				
					
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						// ... | 
				
			
			
		
	
		
		
			
				
					
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						'components' => array( | 
				
			
			
		
	
		
		
			
				
					
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							'session' => array( | 
				
			
			
		
	
		
		
			
				
					
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								'class' => 'yii\web\DbSession', | 
				
			
			
		
	
		
		
			
				
					
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								// Set the following if want to use DB component other than | 
				
			
			
		
	
		
		
			
				
					
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								// default 'db'. | 
				
			
			
		
	
		
		
			
				
					
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								// 'db' => 'mydb', | 
				
			
			
		
	
		
		
			
				
					
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								// To override default session table set the following | 
				
			
			
		
	
		
		
			
				
					
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								// 'sessionTable' => 'my_session', | 
				
			
			
		
	
		
		
			
				
					
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					); | 
				
			
			
		
	
		
		
			
				
					
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					``` | 
				
			
			
		
	
		
		
			
				
					
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					You can use `CacheSession` to store sessions using cache. Note that some | 
				
			
			
		
	
		
		
			
				
					
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					cache storages such as memcached has no guaranteee that session data will not | 
				
			
			
		
	
		
		
			
				
					
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					be lost leading to unexpected logouts. | 
				
			
			
		
	
		
		
			
				
					
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					Improving application | 
				
			
			
		
	
		
		
			
				
					
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					--------------------- | 
				
			
			
		
	
		
		
			
				
					
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					### Using Serverside Caching Techniques | 
				
			
			
		
	
		
		
			
				
					
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					As described in the Caching section, Yii provides several caching solutions that | 
				
			
			
		
	
		
		
			
				
					
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					may improve the performance of a Web application significantly. If the generation | 
				
			
			
		
	
		
		
			
				
					
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					of some data takes long time, we can use the data caching approach to reduce the | 
				
			
			
		
	
		
		
			
				
					
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					data generation frequency; If a portion of page remains relatively static, we | 
				
			
			
		
	
		
		
			
				
					
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					can use the fragment caching approach to reduce its rendering frequency; | 
				
			
			
		
	
		
		
			
				
					
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					If a whole page remains relative static, we can use the page caching approach to | 
				
			
			
		
	
		
		
			
				
					
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					save the rendering cost for the whole page. | 
				
			
			
		
	
		
		
			
				
					
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					### Leveraging HTTP to save procesing time and bandwidth | 
				
			
			
		
	
		
		
			
				
					
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					TBD | 
				
			
			
		
	
		
		
			
				
					
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					### Database Optimization | 
				
			
			
		
	
		
		
			
				
					
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					Fetching data from database is often the main performance bottleneck in | 
				
			
			
		
	
		
		
			
				
					
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					a Web application. Although using caching may alleviate the performance hit, | 
				
			
			
		
	
		
		
			
				
					
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					it does not fully solve the problem. When the database contains enormous data | 
				
			
			
		
	
		
		
			
				
					
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					and the cached data is invalid, fetching the latest data could be prohibitively | 
				
			
			
		
	
		
		
			
				
					
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					expensive without proper database and query design. | 
				
			
			
		
	
		
		
			
				
					
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					Design index wisely in a database. Indexing can make SELECT queries much faster, | 
				
			
			
		
	
		
		
			
				
					
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					but it may slow down INSERT, UPDATE or DELETE queries. | 
				
			
			
		
	
		
		
			
				
					
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					For complex queries, it is recommended to create a database view for it instead | 
				
			
			
		
	
		
		
			
				
					
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					of issuing the queries inside the PHP code and asking DBMS to parse them repetitively. | 
				
			
			
		
	
		
		
			
				
					
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					Do not overuse Active Record. Although Active Record is good at modelling data | 
				
			
			
		
	
		
		
			
				
					
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					in an OOP fashion, it actually degrades performance due to the fact that it needs | 
				
			
			
		
	
		
		
			
				
					
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					to create one or several objects to represent each row of query result. For data | 
				
			
			
		
	
		
		
			
				
					
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					intensive applications, using DAO or database APIs at lower level could be | 
				
			
			
		
	
		
		
			
				
					
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					a better choice. | 
				
			
			
		
	
		
		
			
				
					
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					Last but not least, use LIMIT in your SELECT queries. This avoids fetching | 
				
			
			
		
	
		
		
			
				
					
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					overwhelming data from database and exhausting the memory allocated to PHP. | 
				
			
			
		
	
		
		
			
				
					
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					### Using asArray | 
				
			
			
		
	
		
		
			
				
					
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					A good way to save memory and processing time on read-only pages is to use | 
				
			
			
		
	
		
		
			
				
					
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					ActiveRecord's `asArray` method. | 
				
			
			
		
	
		
		
			
				
					
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					```php | 
				
			
			
		
	
		
		
			
				
					
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					class PostController extends Controller | 
				
			
			
		
	
		
		
			
				
					
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					{ | 
				
			
			
		
	
		
		
			
				
					
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						public function actionIndex() | 
				
			
			
		
	
		
		
			
				
					
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						{ | 
				
			
			
		
	
		
		
			
				
					
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							$posts = Post::find()->orderBy('id DESC')->limit(100)->asArray()->all(); | 
				
			
			
		
	
		
		
			
				
					
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							echo $this->render('index', array( | 
				
			
			
		
	
		
		
			
				
					
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								'posts' => $posts, | 
				
			
			
		
	
		
		
			
				
					
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							)); | 
				
			
			
		
	
		
		
			
				
					
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						} | 
				
			
			
		
	
		
		
			
				
					
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					} | 
				
			
			
		
	
		
		
			
				
					
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					``` | 
				
			
			
		
	
		
		
			
				
					
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					In the view you should access fields of each invidual record from `$posts` as array: | 
				
			
			
		
	
		
		
			
				
					
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					```php | 
				
			
			
		
	
		
		
			
				
					
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					foreach($posts as $post) { | 
				
			
			
		
	
		
		
			
				
					
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						echo $post['title']."<br>"; | 
				
			
			
		
	
		
		
			
				
					
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					} | 
				
			
			
		
	
		
		
			
				
					
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					``` | 
				
			
			
		
	
		
		
			
				
					
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					Note that you can use array notation even if `asArray` wasn't specified and you're | 
				
			
			
		
	
		
		
			
				
					
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					working with AR objects. | 
				
			
			
		
	
		
		
			
				
					
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					### Processing data in background | 
				
			
			
		
	
		
		
			
				
					
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					In order to respond to user requests faster you can process heavy parts of the | 
				
			
			
		
	
		
		
			
				
					
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					request later if there's no need for immediate response. | 
				
			
			
		
	
		
		
			
				
					
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					- Cron jobs + console. | 
				
			
			
		
	
		
		
			
				
					
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					- queues + handlers. | 
				
			
			
		
	
		
		
			
				
					
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					TBD |