Data Sources and EC2 Instances

We start by grabbing an AMI via a data source, and building an instance from it.

Some resources:

1. Terraform data source aws_ami
2. Getting the latest Ubuntu AMI using the aws_ami data source.
3. The AWS API on describing images, which directly correlates to the filter we'll use

Here's the configuration for finding an existing AMI based on some filters and other parameters:

 1# File cloudcasts.tf
 2# Find an official Ubuntu AMI
 3 
 4data "aws_ami" "ubuntu" {
 5    most_recent = true
 6 
 7    filter {
 8        name   = "name"
 9        values = ["ubuntu/images/hvm-ssd/ubuntu-focal-20.04-amd64-server-*"]
10    }
11 
12    filter {
13        name   = "virtualization-type"
14        values = ["hvm"]
15    }
16 
17    filter {
18        name   = "architecture"
19        values = ["x86_64"]
20    }
21 
22    owners = ["099720109477"] # Canonical official
23}

We can see what Terraform will do with this:

1# Make the file standard terraform format
2terraform fmt
3 
4# See if we broke anything
5terraform plan
6# No changes. Infrastructure is up-to-date.

But let's use the AMI we created in our Packer video:

 1# File cloudcasts.tf
 2# Find the AMI we created
 3 
 4data "aws_ami" "app" {
 5  most_recent = true
 6 
 7  filter {
 8    name   = "state"
 9    values = ["available"]
10  }
11 
12  filter {
13    name   = "tag:Component"
14    values = ["app"]
15  }
16 
17  filter {
18    name   = "tag:Project"
19    values = ["cloudcasts"]
20  }
21 
22  filter {
23    name   = "tag:Environment"
24    values = ["staging"]
25  }
26 
27  #filter {
28  #  name   = "name"
29  #  values = ["cloudcast-staging-*-app"]
30  #}
31 
32  owners = ["self"]
33}

Then we can create an ec2 from that AMI with the aws_instance resource.

We can update file cloudcasts.tf to add that resource definition:

 1# File cloudcasts.tf
 2 
 3resource "aws_instance" "cloudcasts_web" {
 4  ami           = data.aws_ami.app.id
 5  instance_type = "t3.small"
 6 
 7  root_block_device {
 8    volume_size = 8 # GB
 9    volume_type = "gp3"
10  }
11}

And then run a plan/apply to see the changes.

1terraform plan
2terraform apply # prompted to confirm