How to get Doctrine to log queries in Symfony2

I'm pretty new to Symfony2, and I'm looking for a way to log SQL queries (including timings) to the same log file as the rest of my application.

From what I can determine from the documentation this should all work out of the box, but after a few hours of trying I can't figure out what I'm doing wrong.

config_dev.yml

monolog:
    handlers:
        doctrine:
            action_level: debug
            type: stream
            path: %kernel.logs_dir%/%kernel.environment%_doctrine.log
            channels: doctrine

config.yml

# Doctrine Configuration
doctrine:
    dbal:
        driver:   "%database_driver%"
        host:     "%database_host%"
        port:     "%database_port%"
        dbname:   "%database_name%"
        user:     "%database_user%"
        password: "%database_password%"
        charset:  UTF8
        logging:  true
        profiling:  true

    orm:
        auto_generate_proxy_classes: "%kernel.debug%"
        auto_mapping: true

I get no log file generated at all. My other logging handler works fine (not listed here).

I'm wondering where I've gone wrong here, but also whether this is really the right approach or if I should implement a new class which implements the SQL Logger, as mentioned here: http://vvv.tobiassjosten.net/symfony/logging-doctrine-queries-in-symfony2/

But I've no idea how to plug that in via the configuration/services in order to make it apply project-wide (I don't want to have to call it in every Controller, for example).

Many thanks for any help!