root module

Root Module (aws/)

The only module you call directly. Child modules are internal.

Files

File	Purpose
main.tf	Module composition + precondition validations
variables.tf	Top-level structured object variables
outputs.tf	Root outputs (33 values)
locals.tf	Component creation flags, cross-module wiring
data.tf	aws_region, aws_caller_identity, aws_availability_zones
versions.tf	Provider requirements

Module Composition (main.tf)

The root module conditionally instantiates four child modules:

module "vpc" {
  count  = local.create_vpc ? 1 : 0
  source = "./modules/vpc"
  # ...
}

module "storage" {
  count  = local.create_storage ? 1 : 0
  source = "./modules/storage"
  # ...
}

module "database" {
  count      = local.create_database ? 1 : 0
  source     = "./modules/database"
  depends_on = [module.vpc]
  # ...
}

module "ecs" {
  count      = local.create_ecs ? 1 : 0
  source     = "./modules/ecs"
  depends_on = [module.vpc, module.storage, module.database]
  # ...
}

Precondition Validations

Three terraform_data resources enforce dependency rules:

1. brms_dependencies: BRMS requires both Database Module and Storage Module
2. agent_dependencies: Agent requires Storage Module
3. vpc_validation: Existing VPC mode requires vpc.id + subnet IDs

Creation Flags (locals.tf)

Boolean flags control which modules are instantiated:

locals {
  create_vpc      = var.vpc != null && var.vpc.create
  create_storage  = var.storage != null
  create_bucket   = local.create_storage && var.storage.create_bucket
  create_database = var.database != null
  create_brms     = var.brms != null
  create_agent    = var.agent != null
  create_ecs      = local.create_brms || local.create_agent
}

Cross-Module Wiring

The root main.tf handles cross-module security group rules:

resource "aws_security_group_rule" "database_from_brms" {
  count                    = local.create_brms && local.create_database ? 1 : 0
  type                     = "ingress"
  from_port                = 5432
  to_port                  = 5432
  protocol                 = "tcp"
  source_security_group_id = module.ecs[0].brms_tasks_security_group_id
  security_group_id        = module.database[0].security_group_id
}

This allows BRMS ECS tasks to connect to the Aurora database. See Security Architecture for details.

Data Flow

See Variable System for how configuration flows from root variables to child modules.