Terragrunt for Beginners
Terragrunt Blocks
dependencies Block
The dependencies block in Terragrunt ensures that modules are applied in a specific order when running commands like terragrunt run-all. By listing paths to prerequisite modules, you guarantee that upstream infrastructure is provisioned before downstream modules execute.
Key Attribute
| Attribute | Type | Description |
|---|---|---|
| paths | list(string) | A list of relative paths to modules that must finish before the current module. |
Note
The dependencies block only enforces execution order. It does not retrieve outputs from those modules. To reference outputs, use the dependency block with config_path and outputs.
Usage Scenario
Imagine you have defined VPC and EC2 modules, and you want to add an S3 bucket that should only be provisioned after the EC2 instance. Even though the S3 bucket doesn’t consume any EC2 outputs, you can enforce this order:
terraform {
source = "tfr://terraform-aws-modules/s3-bucket/aws//?version=4.1.2"
}
include "root" {
path = find_in_parent_folders()
expose = true
}
include "common" {
path = find_in_parent_folders("common.hcl")
expose = true
}
dependencies {
paths = ["../ec2"]
}
inputs = {
bucket = include.common.locals.project
}
Applying with terragrunt run-all
From the root configuration directory, run:
terragrunt run-all apply
This command applies the EC2 module under ../ec2 first, then provisions the S3 bucket, preserving the correct module sequence and preventing race conditions.
Links and References
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