terraform aws_s3_bucket region that is different to the aws provider region gets created in the same provider region

Question

I would like to manage AWS S3 buckets with terraform and noticed that there's a region parameter for the resource.

I have an AWS provider that is configured for 1 region, and would like to use that provider to create S3 buckets in multiple regions if possible. My S3 buckets have a lot of common configuration that I don't want to repeat, so i have a local module to do all the repetitive stuff....

In mod-s3-bucket/main.tf, I have something like:

variable bucket_region {}
variable bucket_name {}

resource "aws_s3_bucket" "s3_bucket" {
   region = var.bucket_region
   bucket = var.bucket_name
}

And then in main.tf in the parent directory (tf root):

provider "aws" {
  region = "us-east-1"
}

module "somebucket" {
  source = "mod-s3-bucket"
  bucket_region = "us-east-1"
  bucket_name = "useast1-bucket"
}

module "anotherbucket" {
  source = "mod-s3-bucket"
  bucket_region = "us-east-2"
  bucket_name = "useast2-bucket"
}

When I run a terraform apply with that, both buckets get created in us-east-1 - is this expected behaviour? My understanding is that region should make the buckets get created in different regions.

Further to that, if I run a terraform plan after bucket creation, I see the following:

       ~ region                      = "us-east-1" -> "us-east-2"

on the 1 bucket, but after an apply, the region has not changed.

I know I can easily solve this by using a 2nd, aliased AWS provider, but am asking specifically about how the region parameter is meant to work for an aws_s3_bucket resource (https://www.terraform.io/docs/providers/aws/r/s3_bucket.html#region)

terraform v0.12.24
aws v2.64.0

theonlyrao theonlyrao · Accepted Answer · 2020-06-04T23:08:11

I think you'll need to do something like the docs show in this example for Replication Configuration: https://www.terraform.io/docs/providers/aws/r/s3_bucket.html#using-replication-configuration

# /root/main.tf

provider "aws" {
  region = "us-east-1"
}

provider "aws" {
  alias  = "us-east-2"
  region = "us-east-2"
}

module "somebucket" {
  source = "mod-s3-bucket"
  bucket_region = "us-east-1"
  bucket_name = "useast1-bucket"
}

module "anotherbucket" {
  source = "mod-s3-bucket"
  provider = "aws.us-east-2"
  bucket_region = "us-east-2"
  bucket_name = "useast2-bucket"
}

# /mod-s3-bucket/main.tf

variable provider {
   type = string
   default = "aws"
}
variable bucket_region {}
variable bucket_name {}

resource "aws_s3_bucket" "s3_bucket" {
   provider = var.provider
   region = var.bucket_region
   bucket = var.bucket_name
}

I've never explicitly set the provider like that though in a resource but based on the docs it might work.

terraform aws_s3_bucket region that is different to the aws provider region gets created in the same provider region

2 Answers