Fetch What Already Exists: Data Sources

data "TYPE" "LOCAL_NAME" {
  # Filter arguments to find the target
  argument_1 = "value"
}

# Reference anywhere in the configuration:
resource "aws_instance" "app" {
  ami = data.TYPE.LOCAL_NAME.id
}

data "aws_ami" "ubuntu_latest" {
  most_recent = true
  owners      = ["099720109477"] # Canonical's Official AWS Account ID

  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-jammy-22.04-amd64-server-*"]
  }

  filter {
    name   = "virtualization-type"
    values = ["hvm"]
  }
}

resource "aws_instance" "web" {
  ami           = data.aws_ami.ubuntu_latest.id
  instance_type = "t3.micro"
}

# 1. Fetch the default VPC or query by tag
data "aws_vpc" "selected" {
  default = true
}

# 2. Fetch all public subnet IDs inside that VPC
data "aws_subnets" "public" {
  filter {
    name   = "vpc-id"
    values = [data.aws_vpc.selected.id]
  }
}

# 3. Use the first subnet to launch an instance
resource "aws_instance" "web" {
  ami       = data.aws_ami.ubuntu_latest.id
  subnet_id = data.aws_subnets.public.ids[0]
}

data "aws_caller_identity" "current" {}
data "aws_region" "current" {}

# Outputs contextual information
output "account_id" {
  value = data.aws_caller_identity.current.account_id
}

output "region_name" {
  value = data.aws_region.current.name
}