This happens to me so often and I always forget. Basically, the format is specific to the backend, so you have to add this to your config:

config :logger, :console,
      metadata: [:request_id],
      format: "$time $metadata[$level] $metadata[$request_id] $message\n"

Edit: and IIRC $metadata is just a list of the metadata variables. So you can’t “access” it. So you’re format probably should be: format: "$time $metadata[$level] $message\n" or you’ll just repeat $metadata twice (and I don’t think $request_id will expand to anything at all)