ramesharun / iac-demo

This repository contains HCL code for deploying an application on AWS.

IAC Demo

How this repository works

This repository contains HCL code for deploying a small application on AWS.

The following AWS infrastructure resources are deployed by the stack:

• VPC
• Public subnets
• Internet Gateway
• Route53 hosted zone
• ACM certificate for the domain
• Application load balancer
• Autoscaling group of EC2 instances with launch configuration.

The application is composed by a nginx server running on Linux ubuntu 18.04 and can be deployed on two environments:

• staging
• production

The folder environment contains the variable files (.tfvars files) and the backend configuration (.conf files) used by Terraform for deploying these environments

The develop branch can be used for performing modifications of the stack on staging environment, before being merged on the main branch for deploying the production environment.

Note: The application is publicly accessible from anywhere in production environment whereas in the staging environment it is limited to specific IP addresses ranges (see cidr_blocks variable).

Pre-requisites for deploying the application

• You need an AWS account with full rights on the following services : VPC, EC2, Route53, ACM, Autoscaling, S3.
• You need to download terraform in version >= 0.13
• You need to be owner of the DNS domain specified in the domain_name variable, especially in production where an ACM certificate
• You need a S3 bucket for storing the tfstate of the stack: change the .conf files in environment folder (one per environment) with your own bucket and its region

When deploying for the first time the production environment, a certificate is created on ACM with DNS challenge for the validation. So you will have to add the NS of the AWS Route53 hosted zone into your registrar before the completion of the deployment (Terraform will wait for the validation of the certificate before attaching it on the load balancer).

How to deploy the stack

• Initialize your environment with Terraform:

terraform init -backend-config=environment/${ENV}_backend.conf -reconfigure

• Validate the syntax:

terraform validate -var-file=environment/${ENV}.tfvars

• Make a plan of the deployment:

terraform plan -var-file=environment/${ENV}.tfvars

• Apply:

terraform apply -var-file=environment/${ENV}.tfvars -auto-approve

Replace the variable ENV by either staging or prod.

How to access the application

The terraform stack exports two variables:

• load_balancer_url: the public URL of the load balancer in front of your application
• url: the public URL of your application (accessible if you have updated your registrar), pointing to the load balancer url.

How to modify variables of my environment

Variables are located in environment folder. Edit the variables corresponding to your target environment then push the changes according to the previous section.

For a definition of the variables, you can read the description of them in variables.tf file.

How to customize the application

You can change the user data used for initializing the EC2 instances by modifying the user_data.tpl file.

How to connect to the EC2 instances

• Make sure that your public IP address is authorized to access the application
• Customize the value of the public_key variable by adding your own public key
• Connect to the public IP of the EC2 instance of your application using SSH and your private key with the user ubuntu.