Overview

Idea of this codebase is to showcase HA deployment of any web app that can work in Docker without utilizing managed container services. (codebase is opionanted towards wordpress - details in user-data.tpl @ L19).

Important moving parts of the codebase:

• ASG - autoscaling group used to orchestrate AL2 EC2 instances used for the web app
• ALB - loadbalancer used to handle traffic of the ASG
• EFS - elastic file system used as NFS mount to share data volumes in ASG EC2 instances
• RDS - single MySQL RDS instance used for DB layer. HA could be implemented by utilizing additional replicas.

Security

Only externally accessible point of the infrastructure is ALB, it exposes tcp/80 to 0.0.0.0/0 in order to allow HTTP traffic.

RDS and EFS are private, accessible only from the VPC by ASG security group.

Database password is generated randomly utilizing TF random_password resource.

Once the password is generated, it's stored as SecureString SSM parameter.

EC2 instance reads the password in user-data and injects it directly in the Docker container. The password is not exposed in the instance itself.

Even tho codebase is opinionated towards wordpress, simply by modifying user-data.tpl would allow you to run any docker image.

Deployment steps

In order to deploy this codebase to AWS you must have following installed/setup:

1. AWS Account /w IAM user that has required IAM permissions
2. AWS CLI with credentials configured
3. Terraform

Once everything from above is setup, following steps are needed to deploy resources:

# Create S3 bucket for Terraform state
# Not required if the bucket already exists
aws s3 mb s3://<any-unique-name-for-tf-state-bucket>

# Init terraform state, provider and modules
# Either use bucket created above or existing one for `bucket` in `backend-config`
terraform init -backend-config="bucket=<any-unique-name-for-tf-state-bucket>" -backend-config="region=eu-west-1"

# Optionally, create `terraform.tfvars` file to override any of the variables from `variables.tf`
touch terraform.tfvars
vi terraform.tfvars # add overrides

# Apply terraform to deploy resources
terraform apply
# Once the apply command is executed, you will see `app_url` Output where your app is deployed and live.

Utilizing Terraform workspaces is a good idea if you plan on deploying multiple instances of this codebase in the same account.

At the very least, you have to specify 2 variables without default values, check terraform.tfvars.example for more details.

For list of all Terraform variables scroll down to Terraform details section.

Terraform details

Requirements

No requirements.

Providers

Name	Version
aws	n/a

Inputs

Name	Description	Type	Default	Required
asg_cpu_metric_down_threshold	CPUUtilization Auto scaling policy metric threshold to scale-down.	string	"10"	no
asg_cpu_metric_period	CPUUtilization Auto scaling policy metric period in seconds.	string	"60"	no
asg_cpu_metric_up_threshold	CPUUtilization Auto scaling policy metric threshold to scale-up.	string	"40"	no
asg_desired_capacity	Desired capacity of the ASG.	number	1	no
asg_instance_type	Instance type of the ASG.	string	"t3.micro"	no
asg_max_size	Maximum size of the ASG.	number	5	no
asg_min_size	Minimum size of the ASG.	number	1	no
db_engine_version	Version of the MySQL engine to use.	string	"5.7.30"	no
db_instance_class	Instance class used for the RDS.	string	"db.m3.medium"	no
db_name	The DB name to create.	string	n/a	yes
db_username	Username for the master DB user.	string	"dbuser"	no
env	Name of the environment resources are deployed to. (ex. my-super-project-dev)	string	n/a	yes
region	Region where AWS provider will be initialized.	string	"eu-west-1"	no
subnets_to_use	List of default subnets to use.	list(string)	[ "a", "b", "c" ]	no

Outputs

Name	Description
app_dns_name	DNS Name of the App ALB.
app_url	URL of the App.