Infrastructure as Code, 2nd Edition

Chapter 17. Using Stacks as Components

A stack is usually the highest-level component in an infrastructure system. It’s the largest unit that can be defined, provisioned, and changed independently. The reusable stack pattern (see “Pattern: Reusable Stack”) encourages you to treat the stack as the main unit for sharing and reusing infrastructure.

Infrastructures composed of small stacks are more nimble than large stacks composed of modules and libraries. You can change a small stack more quickly, easily, and safely than a large stack. So this strategy supports the virtuous cycle of using speed of change to improve quality, and high quality to enable fast change.

Building a system from multiple stacks requires keeping each stack well-sized and well-designed, cohesive and loosely coupled. The advice in Chapter 15 is relevant to stacks as well as other types of infrastructure components. The specific challenge with stacks is implementing the integration between them without creating tight coupling.

Integration between stacks typically involves one stack managing a resource that another stack uses. There are many popular techniques to implement discovery and integration of resources between stacks, but many of them create tight coupling that makes changes more difficult. So this chapter explores different approaches from a viewpoint of how they affect coupling.

Discovering Dependencies Across Stacks

The ShopSpinner system includes a consumer stack, application-infrastructure-stack ...