Magento 2.0.18 is the final 2.0.x release. After March 2018, Magento 2.0.x will no longer receive security patches, quality fixes, or documentation updates.
To maintain your site's performance, security, and PCI compliance, upgrade to the latest version of Magento.

Magento logging in more detail

Monolog

Magento 2 complies with the PSR-3 standard. By default, Magento uses Monolog. Monolog implemented as a preference for Psr\Log\LoggerInterface in the Magento application di.xml.

Monolog is a popular PHP logging solution with a wide range of handlers that enable you to build advanced logging strategies. Following is a summary of how Monolog works.

A Monolog logger is a channel that has its own set of handlers. Monolog has a large number of handlers, including:

  • Log to files and syslog
  • Send alerts and e-mails
  • Log specific servers and networked logging
  • Logging in development (integration with FireBug and ChromePHP, among others)
  • Log to the database

Each handler can either process the input message and stop propagation or pass the control to the next handler in a chain.

Log messages can be processed in many different ways. For example, you can store all debug information into a file on disk, put the messages with higher log levels into a database, and finally send messages with log level “critical” by e-mail.

Other channels can have a different set of handlers and logic.

Get started with logging

To start working with a logger, you must get a \Psr\Log\LoggerInterface instance. One way to do that is illustrated in our database logging example.

Another way follows:

class SomeModel
 {
     private $logger;

     public function __construct(\Psr\Log\LoggerInterface $logger)
     {
         $this->logger = $logger;
     }

     public function doSomething()
     {
         try {
             //do something
         } catch (\Exception $e) {
             $this->logger->critical('Error message', ['exception' => $e]);
         }
     }
 }

The preceding example shows that SomeModel receives a \Psr\Log\LoggerInterface object using constructor injection. In a method doSomething, if some error occurred, it’s logged to a method critical ($this->logger->critical($e);).

RFC 5424 defines eight log levels (debug, info, notice, warning, error, critical, alert, and emergency).

Next

Example—logging database activity