How to do Infrastructure as Code with Terraform and how to scale its code

1. Infrastructure as
Code - Terraform
Mathieu Herbert
@MathieuHerbert

2. Manage Cloud
Infrastructure

7. “codifies APIs into
declarative configuration
files that can be shared
amongst team members,
treated as code, edited,
reviewed, and versioned.”
terraform.io

8. Hashicorp

9. Terraform

10. Terraform

11. Topology
Provider
TfState
2. Call APIs
1. Get State
3. Push State

12. “The goal of HCL is to build a
structured configuration
language that is both human
and machine friendly for use
with command-line tools, but
specifically targeted towards
DevOps tools, servers, etc.”
Topology: Hashicorp Configuration Language files
terraform.io

13. Resource
Unitary element deployed through Provider API
Resource type Resource name
Parameters
resource ”aws_instance” ”web” {
ami = ”ami-12345”
instance_type = ”t2.micro”
…
tags {
Name = ”My Instance”
}
}

14. Variable
Variables can be set through
- Default Value
- tfvars file
- Environment variable
- Command Line Option
Parameters# terraform.tfvars
ubuntu_ami = "ami_23456"
# topology.tf
variable ”ubuntu_ami” {
default = ”ami-12345”
type = ”string”
}
resource ”aws_instance” ”web” {
ami = ”${var.ubuntu_ami}”
instance_type = ”t2.micro”
…
instance_type {
Name = ”My Instance”
}
}

15. Terraform-cli:
Demo Time

16. Terraform graph
Network Subnet A
Firewall
Subnet B
VM A
VM B

17. Terraform apply and idempotency
terraform-cli
Provider
TfState1. Get resources Ids existing in tfstate
2. Get Data from Provider from the ids in
the tfsate
3. Generate graph from Code and 2.
What needs to be created / Modified /
Deleted ?
4. Apply

18. Layer Architecture

19. Network
Firewall
Load Balancer
Application

20. Infrastructure lifecycle
Firewall
App A + Route A
App B + Route B
Network
Load Balancer

21. Terraform Project Structure
01_network
variables.tf
topology.tf
output.tf
02_application_A
variables.tf
topology.tf
output.tf
02_application_B
variables.tf
topology.tf
output.tf
📁
📁
📁

22. How to manage dependencies
between topologies?

23. Datasource
Topology
Network
Tfstate
Network
Tfstate
Application
Topology
Application
Provider
1. Create Resources
with tags
2. Retrieve resource
information based
on tags

24. - Number of Datasources types
depends on provider
- Multiple fields can be
available
- Datasources are refresh on
each apply
Datasource
# topology.tf
data “aws_vpc” “my_vpc” {
tags {
Name = ”My VPC”
}
}
resource ”aws_subnet” ”example” {
vpc_id = "${data.aws_vpc.my_vpc.id}"
availability_zone = "us-west-2a"
cidr_block =
"${cidrsubnet(data.aws_vpc.my_vpc.cidr
_block, 4, 1)}"
}

25. If the resource was created
before Terraform you can
reference it !

26. Create our Application
topology !

27. Modules

28. Abstraction with modules
Topology
Application A
Topology
Application B
Module: Application
Parameters:
- VPC
- Environment
- Instance Type
Resources:
- Instance
- Security Group
Outputs:
- Instance DNS
- Environment

29. Abstraction with modules
Sources:
● Local
● HTTP
● S3
● Github
● Terraform Registry
module ”application” {
source = ”./modules/application”
instance_type = ”m5.large”
environment = ”production”
}

30. Use the Application Module

31. How to work with one code but
different environments?

32. Terraform Project Structure
DEV
STAGING
PROD
01_network
variables.tf
topology.tf
output.tf
02_application_A
variables.tf
topology.tf
output.tf
02_application_B
variables.tf
topology.tf
output.tf
dev.tfvars
staging.tfvars
production.tfvars
📁
📁
📁

33. Workspaces on Terraform
terraform workspace new dev
terraform apply --var-file ../dev.tfvars
DEV
STAGING
terraform workspace new staging
terraform apply --var-file ../staging.tfvars

34. Deploy our Application !

35. Conclusion