DefaultProjectSf5/config/packages/test/monolog.yaml

monolog:
    handlers:
        main:
            type: fingers_crossed
            action_level: error
            handler: nested
            excluded_http_codes: [404, 405]
            channels: ["!event"]
        nested:
            type: stream
            path: "%kernel.logs_dir%/%kernel.environment%.log"
            level: debug