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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).

diagram

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.