services.yml

services.yml

services:
    foo.logger:
        class: Monolog\Logger
        arguments:
            - foo_log
        calls:
            - [ pushHandler, [ @foo.logger.handler ] ] 

    foo.logger.handler:
        class: Monolog\Handler\StreamHandler
        arguments:
            - %kernel.logs_dir%/foo.log
        public: false