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Decide on Terraform Configuration Pattern for Application Repositories

Context and Problem Statement​

The infrastructure monorepo that exists within an organization is responsible for configuring the core infrastructure of the organization: AWS accounts, VPCs, Kubernetes clusters, Route53, etc. However, AWS resources and/or other dependencies specific to a single application — such as a single S3 bucket — is not in the scope of the infrastructure monorepo, and should be managed externally, such that developers responsible for the application in question can manage its dependencies via infrastructure-as-code.

Considered Options​

In-repo Terraform​

A Terraform configuration can be placed within the application repository and automated using atmos. This Terraform configuration requires the infra-state.mixin.tf mixin in order to be able to read the state of components in the infrastructure monorepo, for example from the eks component.

Implementation​

This implementation is described in detail in the following guide: How to Manage Terraform Dependencies in Micro-service Repositories .

Scope​

The Terraform configuration within the application repository should have resources pertaining specifically to that application, specifically for the regional stack configured by atmos (see previous section). This includes:

  • An IAM Role for a ServiceAccount for that application (see: IRSA)

  • An S3 bucket for the application

  • An SNS topic for the application

  • etc.

These Terraform resources are not limited to the AWS provider. Other valid types of resources include:

  • LaunchDarkly Feature Flags

  • Datadog Monitors

References​