Terraform multiple instances but by separate execution - amazon-web-services

Question

I am trying to create AWS instances with load balancer, security group and three instances ---> GROUP 1
I can do this by declaring appropriate resources.
Now I want to create multiples of such instances which are independent of previous instances ---> GROUP 2
I want this because of security of the GROUPS that one group's information should not overlap with other's.
I tried to look up a lot, but couldn't find an approach.
Below is an example of instance:
resource "aws_instance" "node" {
ami = data.aws_ami.ubuntu.id
subnet_id = aws_subnet.development-private-1a.id
key_name = aws_key_pair.nodes.key_name
instance_type = var.instance_type
vpc_security_group_ids = [aws_security_group.dev-ec2-sg.id]
tags = {
Name = "${var.app_name}"
#Environment = "production"
}
root_block_device {
volume_type = "gp2"
volume_size = 8
delete_on_termination = true
}
user_data = file("install_apache.sh")
}
resource "aws_lb_target_group_attachment" "node" {
target_group_arn = aws_lb_target_group.dev.arn
target_id = aws_instance.node.id
port = 80
}
I want to add multiple of these instances with different security groups and load balancers and all other stuff. but I dont want to add additional copies of the same in the terraform file. I want that those instances are independent of this one but then the problem I am facing is that terraform manipulates this instance only.

Answer 1

Based on the comments, you could consider organization of your instance code and its dependents (e.g. target group attachment) as terraform (TF) modules. Also since you are wish to create multiple instance of the same type, you could consider using aws_autoscaling_group which would allow you to not only easily create multiple instance but also easily to manage them.
Subsequently, you could define a module as followed. Below is only partial example. I also do not use aws_autoscaling_group, but create multiple instance using count:
./module/ec2/main.tf
variable "subnet_id" {}
variable "app_name" {}
variable "key_pair" {}
variable "security_group_id" {}
variable "target_group_arn" {}
variable "instance_count" {
default = 1
}
data "aws_ami" "ubuntu" {
# ...
}
resource "aws_instance" "node" {
count = var.instance_count
ami = data.aws_ami.ubuntu.id
subnet_id = var.subnet_id
key_name = var.key_pair
instance_type = var.instance_type
vpc_security_group_ids = [var.security_group_id]
tags = {
Name = "${var.app_name}"
#Environment = "production"
}
root_block_device {
volume_type = "gp2"
volume_size = 8
delete_on_termination = true
}
user_data = file("install_apache.sh")
}
resource "aws_lb_target_group_attachment" "node" {
count = var.instance_count
target_group_arn = var.target_group_arn
target_id = aws_instance.node[count.index].id
port = 80
}
# some outputs skipped
Having such module, in your parent file/module you would create GROUP 1 and 2 instance as follows (again, just partial example):
./main.tf
# resoruces such as LB, SGs, subnets, etc.
module "group1" {
source = "./module/ec2/"
instance_count = 3
security_group_id = <security-group-id1>
target_group_arn = aws_lb_target_group.dev.arn
# other parameters
}
module "group2" {
source = "./module/ec2/"
instance_count = 3
security_group_id = <security-group-id2>
target_group_arn = aws_lb_target_group.dev.arn
# other parameters
}