I was looking into the new Events system for Drupal 8 and there's something I haven't been able to figure out.

I need to dispatch an event when a user logs something to the watchdog table using the new logging API.

// Logs a notice
// Logs an error


I already define a new Event in a custom module but I don't know what needs to be created so when a module logs/adds information to the watchdog table using the code above my event gets triggered.


  • 1
    That is still a hook, not an event (hook_user_login())
    – Berdir
    Apr 30 '18 at 7:57
  • So you have a custom module that logs a message and at the same time fires a custom 'event'? Unless I misunderstand, have you looked at creating an event listener? symfony.com/doc/current/event_dispatcher.html
    – BWagner
    Apr 30 '18 at 15:07
  • Hi guys, thanks for your answer. I don't really want to log a message with my custom module, I want my module to react when a message has been log on the watchdog table. In other words, I need to trigger a function in my custom module when an error is logged in the watchdog table. May 7 '18 at 7:27
  • When In ran the drupal debug:event, I can't see an event for the logger class. So I don't know how to create an event which gets trigger when Drupal core logs in an error on the watchdog table. Does someone knows how to do that one? :) May 7 '18 at 7:32

Once you get the event working, all you have to do is create an instance of the Logger Class in the Logger folder inside your module.

In here: /drupal_root/web/module/custom/my_module/src/Logger

And the class will be something like:

namespace Drupal\my_module\Logger;

use Drupal\Core\Logger\RfcLoggerTrait;
use Psr\Log\LoggerInterface;

class SendToEmail implements LoggerInterface {

  use RfcLoggerTrait;

   * Logs with an arbitrary level.
   * @param mixed $level
   * @param string $message
   * @param array $context
   * @return void
  public function log($level, $message, array $context = []) {
    //Building the parameters for the email
    $params['level'] = $level;
    $params['message'] = $message;
    $params['context'] = $context;

   * @param array $params
   * @return null
  public function sendEmail($params = array()){
    //Variable declaration
    $module = 'my_module';
    $key = 'my_module_message';
    $to = "email@email.com";
    $from = "email@email.com";
    $language_code = \Drupal::service('language_manager')->getDefaultLanguage()->getId();
    $send_now = TRUE;

   $mail = \Drupal::service('plugin.manager.mail')->mail($module, $key, $to, $language_code, $params, $from, $send_now);
    return $mail;

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