Terraform Advanced — Terragrunt Dependency Blocks

Reference outputs from other stacks without terraform_remote_state data sources.

---

The dependency Block

# environments/prod/eks/terragrunt.hcl
include "root" {
  path = find_in_parent_folders()
}

terraform {
  source = "../../../modules/eks"
}

dependency "vpc" {
  config_path = "../vpc"
}

dependency "rds" {
  config_path = "../rds"
}

inputs = {
  vpc_id     = dependency.vpc.outputs.vpc_id
  subnet_ids = dependency.vpc.outputs.private_subnet_ids
  db_host    = dependency.rds.outputs.endpoint
}

---

How It Works

terragrunt apply (in prod/eks/)
  1. Detects dependency on prod/vpc/ and prod/rds/
  2. Reads their state files to get outputs
  3. Passes outputs as inputs to the EKS module

---

Mock Outputs (for plan Before Dependencies Exist)

dependency "vpc" {
  config_path = "../vpc"

  mock_outputs = {
    vpc_id             = "vpc-mock"
    private_subnet_ids = ["subnet-mock-1", "subnet-mock-2"]
  }
  mock_outputs_allowed_terraform_commands = ["plan", "validate"]
}

💡 Production Tip: Mock outputs let you terragrunt plan before dependencies are applied — essential for CI/CD pipelines.

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What’s Next?

Apply entire folder trees with run-all.

← Remote State Config run-all Commands →