How to write log in Magento 2

In order to write the log in Magento 2, it is compulsory to use Monolog Library for the purpose of the logging. In this article, Mageplaza will point you to work with Monolog’s Logger class at MAGENTO_ROOT/vendor/monolog/monolog/src/Monolog/Logger.php. Two steps are covered to show the instruction clearly.

Overview of writing the log in Magento 2

  • Step 1: Write the custom log in your module
  • Step 2: Flush Cache and check result

Step 1: Write the custom log in your module

In your module, please use one of the function app/code/Mageplaza/HelloWorld/Block/Post.php. In the guide today, you will see some types of logs such as info, alert, notice, critical, error, and debug in the following code. However, remember that all of them are archived in system.log file expecting from the debug log that is in debug.log file

<?php
namespace Mageplaza\HelloWorld\Post;
class Post extends \Magento\Framework\View\Element\Template
{
        protected $_logger;
 
    public function __construct(
        \Magento\Backend\Block\Template\Context $context,
        \Psr\Log\LoggerInterface $logger,
        array $data = []
    )
    {        
        $this->_logger = $logger;
        parent::__construct($context, $data);
    }
    
    public function testLogging() 
    {    
        // monolog's Logger class
        // MAGENTO_ROOT/vendor/monolog/monolog/src/Monolog/Logger.php
        
        // saved in var/log/debug.log
        $this->_logger->debug('debug1234'); 
        //Output: [2017-02-22 04:48:44] main.DEBUG: debug1234 {"is_exception":false} []
        
        $this->_logger->info('info1234'); 
        // Write to default log file: var/log/system.log
        //Output: [2017-02-22 04:52:56] main.INFO: info1234 [] []
        
        $this->_logger->alert('alert1234'); 
        // Write to default log file: var/log/system.log
        //Output: [2017-02-22 04:52:56] main.ALERT: alert1234 [] []
        
        $this->_logger->notice('notice1234'); 
        // Write to default log file: var/log/system.log
        //Output: [2017-02-22 04:52:56] main.NOTICE: notice1234 [] []
        
        // Write to default log file: var/log/system.log
        $this->_logger->error('error1234'); 
        //Output: [2017-02-22 04:52:56] main.ERROR: error1234 [] []
        
         // Write to default log file: var/log/system.log
        $this->_logger->critical('critical1234'); 
        //Output: [2017-02-22 04:52:56] main.CRITICAL: critical1234 [] []
        
        // Adds a log record at an arbitrary level
        $level = 'DEBUG';
        // saved in var/log/debug.log
        $this->_logger->log($level,'debuglog1234', array('msg'=>'123', 'new' => '456')); 
        //Output: [2017-02-22 04:52:56] main.DEBUG: debuglog1234 {"msg":"123","new":"456","is_exception":false} []
        
        // Write to default log file: var/log/system.log
        $level = 'ERROR';
        $this->_logger->log($level,'errorlog1234', array( array('test1'=>'123', 'test2' => '456'), array('a'=>'b') )); 
        //Output: [2017-02-22 04:52:56] main.ERROR: errorlog1234 [{"test1":"123","test2":"456"},{"a":"b"}] []        
        
    }
    
}
?>

Step 2: Flush Cache and check result

Flush Magento cache and check your result.

If you got this error message: Exception printing is disabled by default for security reasons, this topic may help.

That is it! If that you have any queries about the article or any questions in general, use the comment section below!





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