When I used Rails for the first time I was impressed by the use of multiple environments to handle different setup, policies and behavior of an application. A few year ago use of environments wasn’t so common and switching between development, test and production was an innovation for me.
Anyway big projects who use custom frameworks introduced this structure several years before. I had the pleasure to work over a lot of legacy code who implement different environments setup. For example classified ADS channel of Repubblica.it (built by my mentor @FabiolousMate) uses dev, demo and production. Other projects I worked on use staging. After have listened a lot of opinions I asked myself which are the most important environments and if three are enough.
I’m mostly a Ruby developer and I know the Rails ecosystem who uses 3 basic environment.
- development is used to when you code. Source code is reloaded each time. Log is EXTREMELY verbose. Libraries includes debug and error logging features. Database is full of garbage data.
- test is for automatic testing. Data is loaded and cleaned automatically every time you run tests. Everything can be mocked (database, APIs, external services, …). Libraries includes testing frameworks and log is just for test output.
- production is to be safe. Logging is just for errors. Sometimes there is a caching layer. Libraries are loaded once. Data is replicated. Everything is set up to improve both performances and robustness.
These environments are really useful in order to manage application development. Unfortunately are not enough to handle every situation. For example production is not appropriate for testing new feature because of the poor log and the strong optimization (and the precious production data) and is not appropriate as well for demo purpose because has to be used by customers. Development is alike not appropriate to find bottlenecks because of messy data and debug code.
In my experience I usually add three more environment to my application trying to fit every situation. Most of cases these are enough.
- staging is for deep testing of new features. Production data and development logging and libraries. Enable you to test side effects of your new features in the real world. If an edit works here probably works also in production
- demo is for showtime. Production environment with sandboxes features and demo data. You can open this environment to anyone and he can play whatever he wants without dangers.
- profile is to find bottlenecks. Development environment with specific library to profile and fine tuning of you process. You can adjust data to stress your system without worry about coherence of data.
This is IMHO a good setup of you deploy environments. Depending on projects some of these aren’t useful but in a large project each one can save you life.