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Module: utils

This terraform-aws-utils module provides some simple utilities to use when working in AWS.

Introduction​

This terraform-aws-utils module provides some simple utilities to use when working in AWS. More complex utilities are available through Cloud Posse's utils Terraform provider terraform-provider-utils.

Compact Alternative Codes (Abbreviations)​

This module's primary function is to provide compact alternative codes for Regions, Availability Zones, and Local Zones, codes which are guaranteed to use only digits and lower case letters: no hyphens. Conversions to and from official codes and alternative codes are handled via lookup maps.

  • The short abbreviations for regions are variable length (generally 4-6 characters, but length limits not guaranteed) and strictly algorithmically derived so that people can more easily interpret them. The short region code abbreviations typically match the prefix of the Availability Zone IDs in that region, but this is not guaranteed. The short abbreviations for local regions are generally of the form AWS uses, with the region prefix and dashes removed.
  • The fixed abbreviations are always exactly 3 characters for regions and 4 characters for availability zones and local zones, but have some exceptional cases (China, Africa, Asia-Pacific South, US GovCloud) that have non-obvious abbreviations. If a future new region causes a conflict with an established local zone abbreviation, we may change the local zone abbreviation to keep the region mappings consistent. For example, the local zone us-east-1-mci-1a would have been abbreviated mc1a had we released it earlier, and that would have conflicted with the new (in 2022) me-central-1a which would also be abbreviated mc1a in keeping with the general pattern of using the first letter of each of the first 2 parts. We might have chosen to change the abbreviation for us-east-1-mci-1 so we could use mc1a for me-central-1a. (As it happens, we added them both at the same time and avoided this collision.) If we were to make such a change, this would be a breaking change for people using the affected local zone, so we recommend using the short abbreviations if you are using local zones, which are far less likely to have conflicts in the future.
  • The identity "abbreviations" are not abbreviations but are instead the official codes (output equals input, which is why it is called "identity"). This map is provided to simplify algorithmic choice of region code abbreviation when you want to include a "no abbreviation" option.

We currently support Local Zones but not Wavelength Zones. If we support Wavelength Zones in the future, it is likely that the fixed-length abbreviations for them will be non-intuitive, or we may only provide short and not fixed abbreviations for them.

The intention is that existing region mappings will never change, and if new regions or zones are created that conflict with existing ones, they will be given non-standard mappings so as not to conflict. However, as stated above, we may choose to change a local region abbreviation if it conflicts with the obvious abbreviation for a newly created region. We have picked abbreviations for local zones with avoiding such future collisions in mind, but we cannot predict the future. (Both bos and den fit the pattern for region abbreviations, but we do not envision a future bo-south-1 or de-north-1 region.)

ELB Logging​

This module provides Elastic Load Balancing Account IDs per region to be used in configuring S3 Bucket Permissions to allow access logs to be stored in S3.

However, the account IDs have no other purpose, and as AWS expands, it has become more complicated to create the correct bucket policy. The policy for region me-central-1 is different than the policy for us-east-1. So now this module has a new feature: you provide the full AWS region code for the region where logging is to take place (elb_logging_region), and the S3 bucket ARN for where logs are to be stored (elb_logging_bucket_resource_arn), and this module will output the appropriate S3 bucket policy (in JSON) to attach to your S3 bucket.

NOTE: The region must be known at Terraform "plan" time. Use a configuration input, such as what you used to configure the Terraform AWS Provider, not an output from some resource or module.

Region Display Names​

There is no AWS API that reliably returns the human-friendly display name (e.g. "Europe (Stockholm)") given the API-friendly region name. So this module provides region_display_name_map to implement this functionality.

Enabled and Disabled Regions​

For convenience, this module provides lists of enabled and disabled regions in the current account. Note that since these lists are dynamic, they cannot be used in Terraform count or for_each resource expressions.

Usage​

Here's how to invoke this example module in your projects

locals {
  shorten_regions   = true
  naming_convention = local.shorten_regions ? "to_short" : "identity"
  az_map            = module.example.region_az_alt_code_maps[local.naming_convention]
}

module "utils_example_complete" {
  source  = "cloudposse/utils/aws"
  # Cloud Posse recommends pinning every module to a specific version
  # version     = "x.x.x"
}

module "label" {
  source = "cloudposse/label/null"
  # Cloud Posse recommends pinning every module to a specific version
  # version     = "x.x.x"

  attributes = [local.az_map["us-east-2"]]

  context = module.this.context
}

Examples​

Here is an example of using this module: