In this section lets discuss how we can build reusable modules.
Here in this example lets create Ec2 and VPC, subnets dynamically by using separate modules.
Folder structure will be like below
First lets create VPC and subnets.
for this, create below files
network.tf: for vpc ,subnets
resource "aws_vpc" "main" {
cidr_block = var.vpc_cidr
instance_tenancy = var.tenancy
tags = {
Name = "main"
}
}
resource "aws_subnet" "main" {
vpc_id = var.vpc_id
cidr_block = var.subnet_cidr
tags = {
Name = "main"
}
}
output "vpc_id"{
value=aws_vpc.main.id
}
output "subnet_id"{
value=aws_subnet.main.id
}
vars.tf: To initialize the variables , this will be used in vpc and subnets creation.
vars.tf:
variable "vpc_cidr" {
default="10.0.0.0/16"
}
varible "tenancy" {
default=dedicated
}
variable "vpc_id"{
}
variable "subnet_cidr"{
default="10.0.1.0/24" ---> if the value is mandatory initialize the same else assign empty.
}
Now lets create ec2 instance by following the same.
create a file : instances.tf in ec2 folder, in this case get the subnet value where you want to create instance.
instances.tf:
resource "aws_instance" "web" {
count=var.ec2_count
ami = var.ec2_ami
instance_type = "var.instatype
subnet_id=var.subnet_id
tags = {
Name = "myinstance"
}
}
vars.tf
variable "ec2_ami"{ }
variable "instatype"{
default="t2.micro"
}
variable "subnet_id"{ }
variable "ec2_count"{
default="1"
}
Lets use this to create resources in dev and prod environment.
Create two instances
create a main.tf file in dev folder and source is where you are getting the values for CIDR or vpc or subnets.
In case of source , you can get value from anywhere like git/bitbucket or etc with relative path.
We need to get the vpc_id which is dynamically creating in runtime. To get this value from modules/vpc , we need to declare this in output (refer network.tf) file.
Dev:
main.tf:
provider "aws" {
region = "ap-south-1"
}
module "my_vpc"{
source="../modules/vpc"
vpc_cidr="192.168.0.0/16"
tenancy="default"
vpc_id="${module.my_vpc.vpc_id}"
subnet_cidr="192.168.1.0/24"
}
module "my_ec2"{
source="../modules/ec2"
ec2_count=1
ec2_ami="ami-09052aa9bc337c78d"
instatype="t2.micro"
subnet_id="${module.my_vpc.subnet_id}"
}
Now apply terraform and check the output.
VPC:
Same main.tf file we can use it for dev too and update required vpc and subnets , EC2 values and try.
main.tf:
provider "aws" {
region = "ap-south-1"
}
module "my_vpc"{
source="../modules/vpc"
vpc_cidr="10.0.0.0/16"
tenancy="default"
vpc_id="${module.my_vpc.vpc_id}"
subnet_cidr="10.0.1.0/24"
}
module "my_ec2"{
source="../modules/ec2"
ec2_count=1
ec2_ami="ami-09a7bbd08886aafdf"
instatype="t2.micro"
subnet_id="${module.my_vpc.subnet_id}"
}
This is how we can create modules and provision the AWS resources using Terraform.
Thank you for reading
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