How to apply security group rules in different regions? - amazon-web-services

Question

I need help in writing a terraform script fro AWS as follows:
I have a list of security groups in multiple regions, for example,
- us-east-2
- us-west-1
- etc.
Now when I add a new instance in any of the region, I am applying an EIP.
I need to add that EIP all traffic in every region's security group.
So far what I tried:
Saving the EIP in a file called node_ips.txt
Read that file
Apply it to security group
Here is the script sample:
variable "list_eips" { type=list" }
resource "aws_eip_association" "eip_assoc" {
count = "${local.number_of_instances}"
instance_id = "${element(aws_instance.ec2_instance.*.id, count.index)}"
allocation_id = "${element(data.aws_eip.db_ip.*.id, count.index)}"
provisioner "local-exec" {
command = "echo ${self.public_ip} >> node_ips.txt"
}
}
data "template_file" "read_node_ips" {
template = "${file("${path.cwd}/node_ips.txt")}"
}
resource "aws_security_group_rule" "allow_db_communication" {
type = "ingress"
from_port = 0
to_port = 65535
protocol = "tcp"
cidr_blocks = ["${split(",", "${join("/32,", concat(compact(split("\n",data.template_file.read_node_ips.rendered)),var.list_eips) )}/32")}"]
security_group_id = "${data.aws_security_group.cassandra_sg.id}"
}
This is not working for me. It is adding rules only for list_eips.
Again, when I add a new instance in different region, the secruity group is different. So, I am not able to know what was my security group in previous region.
Please advise any idea.
Thanks.

Answer 1

Terraform has the idea of "Multiple Provider Instances", You can create providers for each region that need to access and manipulate resources.
# West coast region
provider "aws" {
alias = "west"
region = "us-west-2"
}
resource "aws_instance" "foo" {
provider = "aws.west"
# ...
}
https://www.terraform.io/docs/configuration/providers.html