terraform-null-label

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

This module generates names using the following convention by default: {namespace}-{environment}-{stage}-{name}-{attributes}. However, it is highly configurable. The delimiter (e.g. -) is configurable. Each label item is optional (although you must provide at least one). So if you prefer the term stage to environment you can exclude environment and the label id will look like {namespace}-{stage}-{name}-{attributes}.

• If attributes are excluded but namespace, stage, and environment are included, id will look like {namespace}-{environment}-{stage}-{name}.
• If you want the attributes in a different order, you can specify that, too, with the label_order list.
• You can set a maximum length for the name, and the module will create a unique name that fits within that length.
• You can control the letter case of the generated labels which make up the id using var.label_value_case.
• The labels are also exported as tags. You can control the case of the tag names (keys) using var.label_key_case.

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 originally referred to the primary Terraform provider used in this module. With Terraform 0.12, this module no longer needs any provider, but the name was kept for continuity.

• Releases of this module from 0.23.0 onward only work with Terraform 0.13 or newer.
• Releases of this module from 0.12.0 through 0.22.1 support HCL2 and are compatible with Terraform 0.12 or newer.
• Releases of this module prior to 0.12.0 are compatible with earlier versions of terraform like Terraform 0.11.

This project is part of our comprehensive "SweetOps" approach towards DevOps.

It's 100% Open Source and licensed under the APACHE2.

We literally have hundreds of terraform modules that are Open Source and well-maintained. Check them out!

Security & Compliance

Security scanning is graciously provided by Bridgecrew. Bridgecrew is the leading fully hosted, cloud-native solution providing continuous Terraform security and compliance.

Benchmark	Description
	Infrastructure Security Compliance
	Center for Internet Security, KUBERNETES Compliance
	Center for Internet Security, AWS Compliance
	Center for Internet Security, AZURE Compliance
	Payment Card Industry Data Security Standards Compliance
	National Institute of Standards and Technology Compliance
	Information Security Management System, ISO/IEC 27001 Compliance
	Service Organization Control 2 Compliance
	Center for Internet Security, GCP Compliance
	Health Insurance Portability and Accountability Compliance

Usage

IMPORTANT: We do not pin modules to versions in our examples because of the difficulty of keeping the versions in the documentation in sync with the latest released versions. We highly recommend that in your code you pin the version to the exact version you are using so that your infrastructure remains stable, and update versions in a systematic way so that they do not catch you by surprise.

Also, because of a bug in the Terraform registry (hashicorp/terraform#21417), the registry shows many of our inputs as required when in fact they are optional. The table below correctly indicates which inputs are required.

Defaults

Cloud Posse Terraform modules share a common context object that is meant to be passed from module to module. The context object is a single object that contains all the input values for terraform-null-label. However, each input value can also be specified individually by name as a standard Terraform variable, and the value of those variables, when set to something other than null, will override the value in the context object. In order to allow chaining of these objects, where the context object input to one module is transformed and passed to the next module, all the variables default to null or empty collections. The actual default values used when nothing is explicitly set are describe in the documentation below.

For example, the default value of delimiter is shown as null, but if you leave it set to null, terraform-null-label will actually use the default delimiter - (hyphen).

A non-obvious but intentional consequence of this design is that once a module sets a non-default value, future modules in the chain cannot reset the value back to the original default. Insted, the new setting becomes the new default for downstream modules. Also, collections are not overwritten, they are merged, so once a tag is added, it will remain in the tag set and cannot be removed, although its value can be overwritten.

Simple Example

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 = {
    "BusinessUnit" = "XYZ",
    "Snapshot"     = "true"
  }
}

This will create an id with the value of eg-prod-bastion-public because when generating id, the default order is namespace, environment, stage, name, attributes (you can override it by using the label_order variable, see Advanced Example 3).

Now reference the label when creating an instance:

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 = {
    "BusinessUnit" = "XYZ",
    "Snapshot"     = "true"
  }
}

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 = {
    "BusinessUnit" = "XYZ",
    "Snapshot"     = "true"
  }
}

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]
}

Advanced Example 2

Here is a more complex example with an autoscaling group that has a different tagging schema than other resources and requires its tags to be in this format, which this module can generate:

tags = [
    {
        key = Name,
        propagate_at_launch = 1,
        value = namespace-stage-name
    },
    {
        key = Namespace,
        propagate_at_launch = 1,
        value = namespace
    },
    {
        key = Stage,
        propagate_at_launch = 1,
        value = stage
    }
]

################################
# terraform-null-label example #
################################
module "label" {
  source    = "../../"
  namespace = "cp"
  stage     = "prod"
  name      = "app"

  tags = {
    BusinessUnit = "Finance"
    ManagedBy    = "Terraform"
  }

  additional_tag_map = {
    propagate_at_launch = "true"
  }
}

#######################
# Launch template     #
#######################
resource "aws_launch_template" "default" {
  # terraform-null-label example used here: Set template name prefix
  name_prefix                           = "${module.label.id}-"
  image_id                              = data.aws_ami.amazon_linux.id
  instance_type                         = "t2.micro"
  instance_initiated_shutdown_behavior  = "terminate"

  vpc_security_group_ids                = [data.aws_security_group.default.id]

  monitoring {
    enabled                             = false
  }
  # terraform-null-label example used here: Set tags on volumes
  tag_specifications {
    resource_type                       = "volume"
    tags                                = module.label.tags
  }
}

######################
# Autoscaling group  #
######################
resource "aws_autoscaling_group" "default" {
  # terraform-null-label example used here: Set ASG name prefix
  name_prefix                           = "${module.label.id}-"
  vpc_zone_identifier                   = data.aws_subnet_ids.all.ids
  max_size                              = "1"
  min_size                              = "1"
  desired_capacity                      = "1"

  launch_template = {
    id                                  = "aws_launch_template.default.id
    version                             = "$$Latest"
  }

  # terraform-null-label example used here: Set tags on ASG and EC2 Servers
  tags                                  = module.label.tags_as_list_of_maps
}

Advanced Example 3

See complete example for even more examples.

This example shows how you can pass the context output of one label module to the next label_module, allowing you to create one label that has the base set of values, and then creating every extra label as a derivative of that.

module "label1" {
  source      = "git::https://github.com/cloudposse/terraform-null-label.git?ref=master"
  namespace   = "CloudPosse"
  environment = "UAT"
  stage       = "build"
  name        = "Winston Churchroom"
  attributes  = ["fire", "water", "earth", "air"]
  delimiter   = "-"

  label_order = ["name", "environment", "stage", "attributes"]

  tags = {
    "City"        = "Dublin"
    "Environment" = "Private"
  }
}

module "label2" {
  source    = "git::https://github.com/cloudposse/terraform-null-label.git?ref=master"
  context   = module.label1.context
  name      = "Charlie"
  stage     = "test"
  delimiter = "+"

  tags = {
    "City"        = "London"
    "Environment" = "Public"
  }
}

module "label3" {
  source    = "git::https://github.com/cloudposse/terraform-null-label.git?ref=master"
  name      = "Starfish"
  stage     = "release"
  context   = module.label1.context
  delimiter = "."

  tags = {
    "Eat"    = "Carrot"
    "Animal" = "Rabbit"
  }
}

label1 = {
  "attributes" = [
    "fire",
    "water",
    "earth",
    "air",
  ]
  "delimiter" = "-"
  "id" = "winstonchurchroom-uat-build-fire-water-earth-air"
  "name" = "winstonchurchroom"
  "namespace" = "cloudposse"
  "stage" = "build"
}
label1_context = {
  "additional_tag_map" = {}
  "attributes" = [
    "fire",
    "water",
    "earth",
    "air",
  ]
  "delimiter" = "-"
  "enabled" = true
  "environment" = "UAT"
  "label_order" = [
    "name",
    "environment",
    "stage",
    "attributes",
  ]
  "name" = "Winston Churchroom"
  "namespace" = "CloudPosse"
  "stage" = "build"
  "tags" = {
    "City" = "Dublin"
    "Environment" = "Private"
  }
}
label1_normalized_context = {
  "additional_tag_map" = {}
  "attributes" = [
    "fire",
    "water",
    "earth",
    "air",
  ]
  "delimiter" = "-"
  "enabled" = true
  "environment" = "uat"
  "id_length_limit" = 0
  "label_order" = [
    "name",
    "environment",
    "stage",
    "attributes",
  ]
  "name" = "winstonchurchroom"
  "namespace" = "cloudposse"
  "regex_replace_chars" = "/[^-a-zA-Z0-9]/"
  "stage" = "build"
  "tags" = {
    "Attributes" = "fire-water-earth-air"
    "City" = "Dublin"
    "Environment" = "Private"
    "Name" = "winstonchurchroom-uat-build-fire-water-earth-air"
    "Namespace" = "cloudposse"
    "Stage" = "build"
  }
}
label1_tags = {
  "Attributes" = "fire-water-earth-air"
  "City" = "Dublin"
  "Environment" = "Private"
  "Name" = "winstonchurchroom-uat-build-fire-water-earth-air"
  "Namespace" = "cloudposse"
  "Stage" = "build"
}
label2 = {
  "attributes" = [
    "fire",
    "water",
    "earth",
    "air",
  ]
  "delimiter" = "+"
  "id" = "charlie+uat+test+fire+water+earth+air"
  "name" = "charlie"
  "namespace" = "cloudposse"
  "stage" = "test"
}
label2_context = {
  "additional_tag_map" = {
    "additional_tag" = "yes"
    "propagate_at_launch" = "true"
  }
  "attributes" = [
    "fire",
    "water",
    "earth",
    "air",
  ]
  "delimiter" = "+"
  "enabled" = true
  "environment" = "UAT"
  "label_order" = [
    "name",
    "environment",
    "stage",
    "attributes",
  ]
  "name" = "Charlie"
  "namespace" = "CloudPosse"
  "regex_replace_chars" = "/[^a-zA-Z0-9-+]/"
  "stage" = "test"
  "tags" = {
    "City" = "London"
    "Environment" = "Public"
  }
}
label2_tags = {
  "Attributes" = "fire+water+earth+air"
  "City" = "London"
  "Environment" = "Public"
  "Name" = "charlie+uat+test+fire+water+earth+air"
  "Namespace" = "cloudposse"
  "Stage" = "test"
}
label2_tags_as_list_of_maps = [
  {
    "additional_tag" = "yes"
    "key" = "Attributes"
    "propagate_at_launch" = "true"
    "value" = "fire+water+earth+air"
  },
  {
    "additional_tag" = "yes"
    "key" = "City"
    "propagate_at_launch" = "true"
    "value" = "London"
  },
  {
    "additional_tag" = "yes"
    "key" = "Environment"
    "propagate_at_launch" = "true"
    "value" = "Public"
  },
  {
    "additional_tag" = "yes"
    "key" = "Name"
    "propagate_at_launch" = "true"
    "value" = "charlie+uat+test+fire+water+earth+air"
  },
  {
    "additional_tag" = "yes"
    "key" = "Namespace"
    "propagate_at_launch" = "true"
    "value" = "cloudposse"
  },
  {
    "additional_tag" = "yes"
    "key" = "Stage"
    "propagate_at_launch" = "true"
    "value" = "test"
  },
]
label3 = {
  "attributes" = [
    "fire",
    "water",
    "earth",
    "air",
  ]
  "delimiter" = "."
  "id" = "starfish.uat.release.fire.water.earth.air"
  "name" = "starfish"
  "namespace" = "cloudposse"
  "stage" = "release"
}
label3_context = {
  "additional_tag_map" = {}
  "attributes" = [
    "fire",
    "water",
    "earth",
    "air",
  ]
  "delimiter" = "."
  "enabled" = true
  "environment" = "UAT"
  "label_order" = [
    "name",
    "environment",
    "stage",
    "attributes",
  ]
  "name" = "Starfish"
  "namespace" = "CloudPosse"
  "regex_replace_chars" = "/[^-a-zA-Z0-9.]/"
  "stage" = "release"
  "tags" = {
    "Animal" = "Rabbit"
    "City" = "Dublin"
    "Eat" = "Carrot"
    "Environment" = "Private"
  }
}
label3_normalized_context = {
  "additional_tag_map" = {}
  "attributes" = [
    "fire",
    "water",
    "earth",
    "air",
  ]
  "delimiter" = "."
  "enabled" = true
  "environment" = "uat"
  "id_length_limit" = 0
  "label_order" = [
    "name",
    "environment",
    "stage",
    "attributes",
  ]
  "name" = "starfish"
  "namespace" = "cloudposse"
  "regex_replace_chars" = "/[^-a-zA-Z0-9.]/"
  "stage" = "release"
  "tags" = {
    "Animal" = "Rabbit"
    "Attributes" = "fire.water.earth.air"
    "City" = "Dublin"
    "Eat" = "Carrot"
    "Environment" = "Private"
    "Name" = "starfish.uat.release.fire.water.earth.air"
    "Namespace" = "cloudposse"
    "Stage" = "release"
  }
}
label3_tags = {
  "Animal" = "Rabbit"
  "Attributes" = "fire.water.earth.air"
  "City" = "Dublin"
  "Eat" = "Carrot"
  "Environment" = "Private"
  "Name" = "starfish.uat.release.fire.water.earth.air"
  "Namespace" = "cloudposse"
  "Stage" = "release"
}

Makefile Targets

Available targets:

  help                                Help screen
  help/all                            Display help for all targets
  help/short                          This help short screen
  lint                                Lint terraform code

Requirements

Providers

No provider.

Inputs

{
  "additional_tag_map": {},
  "attributes": [],
  "delimiter": null,
  "enabled": true,
  "environment": null,
  "id_length_limit": null,
  "label_key_case": null,
  "label_order": [],
  "label_value_case": null,
  "name": null,
  "namespace": null,
  "regex_replace_chars": null,
  "stage": null,
  "tags": {}
}

Outputs

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Related Projects

Check out these related projects.

• terraform-terraform-label - Terraform Module to define a consistent naming convention by (namespace, environment, stage, name, [attributes])

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Copyright

Copyright © 2017-2021 Cloud Posse, LLC

License

See LICENSE for full details.

Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
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KIND, either express or implied.  See the License for the
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Contributors

Erik Osterman	Andriy Knysh	Igor Rodionov	Sergey Vasilyev	Michael Pereira	Jamie Nelson	Vladimir	Daren Desjardins	Maarten van der Hoef	Adam Tibbing