The Rails 5 Way, Fourth Edition

Chapter 1 Rails Configuration and Environments

[Rails] gained a lot of its focus and appeal because I didn’t try to please people who didn’t share my problems. Differentiating between production and development was a very real problem for me, so I solved it the best way I knew how.

—David Heinemeier Hansson

Rails applications have always been preconfigured with three standard modes of operation: development, test, and production. These modes are basically execution environments and have a collection of associated settings that determine things such as which database to connect to and whether the classes of your application should be reloaded with each request. It is simple to create your own custom environments if necessary.

The current environment ...