2 Writing infrastructure as code

Imagine you’ve created a development environment for a hello-world application. You built it organically, adding new components as you needed them. Eventually, you need to reproduce the configuration for production use, which people can publicly access. You also need to scale production across three geographic regions for high availability.

To do this, you must create and update firewalls, load balancers, servers, and databases in new networks for the production environment. Figure 2.1 shows the complexity of the development environment with the firewall, load balancer, server, and database and the components you need to reproduce in production.

The figure also outlines the differences between development and production. The production configuration needs three servers for high availability, expanded firewall rules to allow all HTTP traffic, and stricter firewall rules for the servers to connect to the database. After reviewing all of the differences, you might have a lot of questions about the best and easiest way to make the changes.

2.1 Expressing infrastructure change

2.2 Understanding immutability

2.2.1 Remediating out-of-band changes

2.2.2 Migrating to infrastructure as code

2.3 Writing clean infrastructure as code

2.3.1 Version control communicates context

2.3.2 Linting and formatting

2.3.3 Naming resources

2.3.4 Variables and constants

2.3.5 Parametrize dependencies