Drupal 8 monolog logging

services.yml

parameters:

  ...
  
  monolog.channel_handlers:
    # Log to a file by default.
    default: ['file']
    # Send the php channel to web server's error log and the browser console:
    # php: ['error_log', 'browser_console']
    # Ignore log entries of "content" channel.
    # content: ['null']
  # Show memory usage on each log entry:
  monolog.processors: ['message_placeholder', 'current_user', 'request_uri', 'memory_usage', 'web']

services:
  # Monolog handlers.
  monolog.handler.file:
      class: Monolog\Handler\RotatingFileHandler
      arguments: ['../logs/application.log', '30', '200', false]

1. Install Drupal 8 monolog module
   composer require drupal/monolog

2. Enable monolog module

3. Add this snippet (except the first 4 lines) to sites/default/services.yml, you can also customize it to use different monolog processors & handlers as you desire

4. Uninstall watchdog module as it will no longer work