Terraform Resources

About Terraform Resources

• Resources are the main thing we want to create with terraform, these are the components that make our infrastructure.
• Terraform intent is to create the resource idempotently, so that running apply more that once will not create multiple resources.
• body of resource contains configuration of attributes of that resource
• each provider (e.g., AWS, Azure, etc.) provides its own set of resources and defines the configuration attributes
• when a resource is created by Terraform, it’s tracked in Terraform state
• resources can refer to attributes of other resources, creating implicit dependencies dependencies trigger sequential creation

HCL Resource examples

• Some resource axamples:
  • aws ec2 instance

1  resource "aws_instance" "web" {
2  ami           = "ami-0005e0cfe09cc9050"
3  instance_type = "t3.micro"
4  tags = {
5    Name = "HelloWorld"
6  }
7}

• aws s3 bucket

1  resource "aws_s3_bucket" "example" {
2  bucket = "my-tf-test-bucket"
3  tags = {
4    Name        = "My bucket"
5    Environment = "Dev"
6  }
7}

• docker container

1resource "docker_container" "foo" {
2  image = docker_image.ubuntu.latest
3  name  = "foo"
4  command = ["/bin/sh", "-c", "--" , "while true; do sleep 30; done;"]
5}

Resources that referenc other resources

• Here's an example of a security-group-rule that refers to the security-group it belongs to:

 1resource "aws_security_group" "web_server" {
 2  name   = "webserver-sg"
 3  vpc_id = "${data.aws_vpc.default.id}"
 4
 5}
 6
 7resource "aws_security_group_rule" "web_server_allow_http_inbound" {
 8  type              = "ingress"
 9  from_port         = "100"
10  to_port           = "2000"
11  protocol          = "tcp"
12  security_group_id = "${aws_security_group.web_server.id}"
13  source_security_group_id = "${aws_security_group.alb.id}"
14}

• In this case, terraform must make sure that the security group is create before the rule is created. This is done automatically.