Tagging Resources

AWS allows developers to tag most resources with up to 50 custom key:value pairs. In Administrative Systems, we have two uses for tags: cost breakdown (from the AWS Cost Explorer), and use with IAM/snapshot/bucket ACL policies.

Beyond our standard tags, developers are free to add additional tags in whatever way makes sense for that application. AWS has some ideas on tagging strategies for things like clusters & security.

Standard Tags

We only require two standard tags. All resources that support tagging should have these tags.

Tag Name	Value	Purpose
Application	The name of your app, which MUST be consistent across envrionments	Cost analysis
Environment	App environment, like dev/QA/prod	Cost analysis

Note that tag names are case-sensitive. Take care to use the correct case for our standard tag names.

Adding these tags across all resources in Terraform is easy:

# Add a tags.tf file, or put these locals in your variables.tf
locals { 
    tags = {
        Application = var.app_name
        Environment = var.env
    }
} 

# And then across (almost) all your TF resource blocks:
resource "aws_s3_bucket" "app_code_bucket" {
  bucket = "my-unique-bucket-name"
  acl    = "private"

  tags = local.tags
}

# If you need to add some additional tags, you can still use the local:
resource "aws_s3_bucket" "app_code_bucket" {
  bucket = "my-unique-bucket-name"
  acl    = "private"

  tags = merge(local.tags, { LambdaSourceCode = true })
}

You can check the Terraform AWS provider documentation for each resource to determine if it supports tags. Alternatively, you can apply tags to every resource and remove them from whatever terraform plan complains about.