README.yaml

name: terraform-null-label
tags:
- aws
- terraform
- terraform-modules
- naming-convention
- name
- namespace
- stage
categories:
- terraform-modules/supported
license: APACHE2
github_repo: cloudposse/terraform-null-label
badges:
- name: Latest Release
  image: https://img.shields.io/github/release/cloudposse/terraform-null-label.svg
  url: https://github.com/cloudposse/terraform-null-label/releases/latest
- name: Slack Community
  image: https://slack.cloudposse.com/badge.svg
  url: https://slack.cloudposse.com
related:
- name: terraform-terraform-label
  description: Terraform Module to define a consistent naming convention by (namespace,
    environment, stage, name, [attributes])
  url: https://github.com/cloudposse/terraform-terraform-label
description: |-
  Terraform module designed to generate consistent names and tags for resources. Use `terraform-null-label` to implement a strict naming convention.

  A label follows the following convention: `{namespace}-{environment}-{stage}-{name}-{attributes}`. The delimiter (e.g. `-`) is configurable.
  The label items are all optional. 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}`

  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](https://github.com/cloudposse?utf8=%E2%9C%93&q=terraform-&type=&language=) 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](https://www.terraform.io/docs/providers/null/index.html) 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.
usage: |-
  ### 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

  ```hcl
  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](#advanced-example-3)).

  Now reference the label when creating an instance:

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

  Or define a security group:

  ```hcl
  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.

  <details><summary>Click to show</summary>

  ```hcl
  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]
  }
  ```

  </details>

  ### 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:

  <details><summary>Click to show</summary>

  ```hcl
  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](examples/autoscalinggroup/main.tf))

  ```hcl
  ################################
  # 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
  }
  ```

  </details>

  ### Advanced Example 3

  See [complete example](./examples/complete) 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.

  <details><summary>Click to show</summary>

  ```hcl
  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:

  ```hcl
  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"
  }

  ```

  </details>

include:
- docs/targets.md
- docs/terraform.md
contributors:
- name: Erik Osterman
  github: osterman
- name: Andriy Knysh
  github: aknysh
- name: Igor Rodionov
  github: goruha
- name: Sergey Vasilyev
  github: s2504s
- name: Michael Pereira
  github: MichaelPereira
- name: Jamie Nelson
  github: Jamie-BitFlight
- name: Vladimir
  github: SweetOps
- name: Daren Desjardins
  github: darend
- name: Maarten van der Hoef
  github: maartenvanderhoef
- name: Adam Tibbing
  github: tibbing