Terraform optional provider for optional resource

Question

I have a module where I want to conditionally create an s3 bucket in another region. I tried something like this:

resource "aws_s3_bucket" "backup" {
   count = local.has_backup ? 1 : 0
   provider = "aws.backup"
   bucket = "${var.bucket_name}-backup"
   versioning { 
     enabled = true
   }
}

but it appears that I need to provide the aws.backup provider even if count is 0. Is there any way around this?

NOTE: this wouldn't be a problem if I could use a single provider to create buckets in multiple regions, see https://github.com/terraform-providers/terraform-provider-aws/issues/8853

Answer 1

Based on your description, I understand that you want to create resources using the same "profile", but in a different region. For that case I would take the following approach:

Create a module file for you s3_bucket_backup, in that file you will build your "backup provider" with variables.

# Module file for s3_bucket_backup
provider "aws" {
  region  = var.region
  profile = var.profile
  alias   = "backup"
}

variable "profile" {
  type            = string
  description     = "AWS profile"
}

variable "region" {
  type            = string
  description     = "AWS profile"
}

variable "has_backup" {
  type            = bool
  description     = "AWS profile"
}

variable "bucket_name" {
  type            = string
  description     = "VPC name"
}

resource "aws_s3_bucket" "backup" {
   count          = var.has_backup ? 1 : 0
   provider       = aws.backup
   bucket         = "${var.bucket_name}-backup"
}

In your main tf file, declare your provider profile using local variables, call the module passing the profile and a different region

# Main tf file
provider "aws" {
  region      = "us-east-1"
  profile     = local.profile
}

locals {
  profile     = "default"
  has_backup  = false
}

module "s3_backup" {
  source            = "./module"
  profile           = local.profile
  region            = "us-east-2"
  has_backup        = true
  bucket_name       = "my-bucket-name"
}

And there you have it, you can now build your s3_bucket_backup using the same "profile" with different regions.

In the case above, the region used by the main file is us-east-1 and the bucket is created on us-east-2.

If you set has_backup to false, it won't create anything.

Since the "backup provider" is build inside the module, your code won't look "dirty" for having multiple providers in the main tf file.