Continuous Delivery - Part 4: Rolling back database migrations with Capistrano rollback

August 14, 2011

According to the book Continuous Delivery, the database also should be under version control, and Rails allows us to achieve this with ActiveRecord Migrations. Even though Capistrano can run the migrations automatically with its deploy command, its deploy:rollback task does not rollback the DB migrations automatically. I’ve created a small capistrano recipe which can take care of rolling back migrations. The assumptions made are:

• All the migrations have the down method defined properly. You can check for this by running rake db:migrate:redo
• The schema.rb exists in the repository. This is one of the suggested practices for Rails.

The script is very simple, it extracts the version from the schema.rb and runs the rake db:migrate with the same version. The task gets run automatically along with deploy:rollback. This approach should work for most small and medium complexity Rails apps.

Continued..

• Continuous Delivery – Part 1: Our Jenkins Build Pipeline setup
• Continuous Delivery – Part 2: Code metrics with metrical
• Continuous Delivery – Part 3: Running custom rake tasks during deployment