Maybe you should specify the version of MySQL in docker-compose.yml:)

[xzycn]

There should be many people facing the similar problem which wasting much time to those don't work with ruby.
When you enter fluxday-app container,and then execute "rake db:migrate",error occured like this: "Mysql2::Error: All parts of a PRIMARY KEY must be NOT NULL:".This is because the newr version of MySQL,
exact 5.7.3+,related link is here.
Well, and there is no explanation that we should to run the series command of rake with Docker,it is a bit confused.
Thanks for your work :)