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 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.

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.

Releases of this module from 0.12.0 onward support HCL2 and only work with Terraform 0.12 or newer. Releases prior to this 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!

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.

Click to show

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:

Click to show

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
    }
]

Autoscaling group using propagating tagging below (full example: autoscalinggroup)

################################
# 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.

Click to show

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"
  }
}

This creates label outputs like this:

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

Name	Version
terraform	>= 0.12.26

Providers

No provider.

Inputs

Name	Description	Type	Default	Required
additional_tag_map	Additional tags for appending to tags_as_list_of_maps. Not added to `tags`.	`map(string)`	`{}`	no
attributes	Additional attributes (e.g. `1`)	`list(string)`	`[]`	no
context	Single object for setting entire context at once. See description of individual variables for details. Leave string and numeric variables as `null` to use default value. Individual variable settings (non-null) override settings in context object, except for attributes, tags, and additional_tag_map, which are merged.	object({ enabled = bool namespace = string environment = string stage = string name = string delimiter = string attributes = list(string) tags = map(string) additional_tag_map = map(string) regex_replace_chars = string label_order = list(string) id_length_limit = number })	{ "additional_tag_map": {}, "attributes": [], "delimiter": null, "enabled": true, "environment": null, "id_length_limit": null, "label_order": [], "name": null, "namespace": null, "regex_replace_chars": null, "stage": null, "tags": {} }	no
delimiter	Delimiter to be used between `namespace`, `environment`, `stage`, `name` and `attributes`. Defaults to `-` (hyphen). Set to `""` to use no delimiter at all.	`string`	`null`	no
enabled	Set to false to prevent the module from creating any resources	`bool`	`null`	no
environment	Environment, e.g. 'uw2', 'us-west-2', OR 'prod', 'staging', 'dev', 'UAT'	`string`	`null`	no
id_length_limit	Limit `id` to this many characters. Set to `0` for unlimited length. Set to `null` for default, which is `0`. Does not affect `id_full`.	`number`	`null`	no
label_order	The naming order of the id output and Name tag. Defaults to ["namespace", "environment", "stage", "name", "attributes"]. You can omit any of the 5 elements, but at least one must be present.	`list(string)`	`null`	no
name	Solution name, e.g. 'app' or 'jenkins'	`string`	`null`	no
namespace	Namespace, which could be your organization name or abbreviation, e.g. 'eg' or 'cp'	`string`	`null`	no
regex_replace_chars	Regex to replace chars with empty string in `namespace`, `environment`, `stage` and `name`. If not set, `"/[^a-zA-Z0-9-]/"` is used to remove all characters other than hyphens, letters and digits.	`string`	`null`	no
stage	Stage, e.g. 'prod', 'staging', 'dev', OR 'source', 'build', 'test', 'deploy', 'release'	`string`	`null`	no
tags	Additional tags (e.g. `map('BusinessUnit','XYZ')`	`map(string)`	`{}`	no

Outputs

Name	Description
additional_tag_map	The merged additional_tag_map
attributes	List of attributes
context	Merged but otherwise unmodified input to this module, to be used as context input to other modules. Note: this version will have null values as defaults, not the values actually used as defaults.
delimiter	Delimiter between `namespace`, `environment`, `stage`, `name` and `attributes`
enabled	True if module is enabled, false otherwise
environment	Normalized environment
id	Disambiguated ID restricted to `id_length_limit` characters in total
id_full	Disambiguated ID not restricted in length
id_length_limit	The id_length_limit actually used to create the ID, with `0` meaning unlimited
label_order	The naming order actually used to create the ID
name	Normalized name
namespace	Normalized namespace
normalized_context	Normalized context of this module
regex_replace_chars	The regex_replace_chars actually used to create the ID
stage	Normalized stage
tags	Normalized Tag map
tags_as_list_of_maps	Additional tags as a list of maps, which can be used in several AWS resources

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Related Projects

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

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Copyright

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

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