terraform-null-label

Terraform module designed to generate consistent label names and tags for resources. Use terraform-null-label to implement a strict naming convention.

A label follows the following convention: {namespace}-{stage}-{name}-{attributes}. The delimiter (e.g. -) is interchangeable.

It's recommended to use one terraform-null-label module for every unique resource of a given resource type. For example, if you have 10 instances, there should be 10 different labels. However, if you have multiple different kinds of resources (e.g. instances, security groups, file systems, and elastic ips), then they can all share the same label assuming they are logically related.

All Cloud Posse modules use this module to ensure resources can be instantiated multiple times within an account and without conflict.

-NOTE: The null refers to the primary Terraform provider used in this module.

Usage

Simple Example

Include this repository as a module in your existing terraform code:

module "eg_prod_bastion_label" {
  source     = "git::https://github.com/cloudposse/terraform-null-label.git?ref=master"
  namespace  = "eg"
  stage      = "prod"
  name       = "bastion"
  attributes = ["public"]
  delimiter  = "-"
  tags       = "${map("BusinessUnit", "XYZ", "Snapshot", "true")}"
}

This will create an id with the value of eg-prod-bastion-public.

Now reference the label when creating an instance (for example):

resource "aws_instance" "eg_prod_bastion_public" {
  instance_type = "t1.micro"
  tags          = "${module.eg_prod_bastion_label.tags}"
}

Or define a security group:

resource "aws_security_group" "eg_prod_bastion_public" {
  vpc_id = "${var.vpc_id}"
  name   = "${module.eg_prod_bastion_label.id}"
  tags   = "${module.eg_prod_bastion_label.tags}"
  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

Advanced Example

Here is a more complex example with two instances using two different labels. Note how efficiently the tags are defined for both the instance and the security group.

module "eg_prod_bastion_abc_label" {
  source     = "git::https://github.com/cloudposse/terraform-null-label.git?ref=master"
  namespace  = "eg"
  stage      = "prod"
  name       = "bastion"
  attributes = ["abc"]
  delimiter  = "-"
  tags       = "${map("BusinessUnit", "ABC")}"
}

resource "aws_security_group" "eg_prod_bastion_abc" {
  name = "${module.eg_prod_bastion_abc_label.id}"
  tags = "${module.eg_prod_bastion_abc_label.tags}"
  ingress {
    from_port   = 22
    to_port     = 22
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

resource "aws_instance" "eg_prod_bastion_abc" {
   instance_type          = "t1.micro"
   tags                   = "${module.eg_prod_bastion_abc_label.tags}"
   vpc_security_group_ids = ["${aws_security_group.eg_prod_bastion_abc.id"}]
} 

module "eg_prod_bastion_xyz_label" {
  source     = "git::https://github.com/cloudposse/terraform-null-label.git?ref=master"
  namespace  = "eg"
  stage      = "prod"
  name       = "bastion"
  attributes = ["xyz"]
  delimiter  = "-"
  tags       = "${map("BusinessUnit", "XYZ")}"
}

resource "aws_security_group" "eg_prod_bastion_xyz" {
  name = "module.eg_prod_bastion_xyz_label.id"
  tags = "${module.eg_prod_bastion_xyz_label.tags}"
  ingress {
    from_port   = 22
    to_port     = 22
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

resource "aws_instance" "eg_prod_bastion_xyz" {
   instance_type          = "t1.micro"
   tags                   = "${module.eg_prod_bastion_xyz_label.tags}"
   vpc_security_group_ids = ["${aws_security_group.eg_prod_bastion_xyz.id}"]
}

Variables

Name	Default	Description	Required
namespace	``	Namespace (e.g. `cp` or `cloudposse`)	Yes
stage	``	Stage (e.g. `prod`, `dev`, `staging`)	Yes
name	``	Name (e.g. `bastion` or `db`)	Yes
attributes	[]	Additional attributes (e.g. `policy` or `role`)	No
tags	{}	Additional tags (e.g. `map("BusinessUnit","XYZ")`	No

WARNING Any tags passed as an input to this module will override the tags generated by this module.

Outputs

Name	Description
id	Disambiguated ID
name	Normalized name
namespace	Normalized namespace
stage	Normalized stage
attributes	Normalized attributes
tags	Normalized Tag map

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