How can I write to Rails logger within my gem
As Frederick Cheung says, you should use a namespaced logger for your gem: MyGem.logger.
Then set it to the Rails logger in a Railtie so that your gem works nicely both inside and outside of Rails.
module MyGem class Railties < ::Rails::Railtie initializer 'Rails logger' do MyGem.logger = Rails.logger end endend
While you should be able to use Rails.logger you might want to consider making the logger that your gem uses configurable, i.e. allow users to set MyGem.logger to whatever logger they want.
You can default it to something that just writes to stdout, in a rails app you can set MyGem.logger = Rails.logger in an initialiser. People who are using your gem outside of rails can do so too.