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08 - AWS Terraform Resources

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Aung Aung Myo Myint
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Table of contents

The building blocks of Terraform configuration start with defining your provider block to specify the cloud platform, such as AWS. The next step is to define the resources you want to create.

What Are Terraform Resources?

Terraform resources represent the infrastructure objects you want to create, such as:

  • EC2 Instances

  • VPCs

  • Databases

  • DNS Records

Each resource block in Terraform describes a single infrastructure object. For example, to launch an EC2 instance, you define a resource block just for that. You can declare multiple resource blocks to create various resources within your infrastructure.

Resource Block Structure

A resource block in Terraform has the following structure:

resource "<RESOURCE_TYPE>" "<LOCAL_NAME>" {
  # Arguments specific to the resource type
  argument_name = "value"
}

  • <RESOURCE_TYPE>: Specifies the type of resource to create (e.g., aws_instance for an EC2 instance).

  • <LOCAL_NAME>: A user-defined name to uniquely identify the resource within the module.

  • Arguments: Define the resource's configuration, such as AMI, instance type, and tags.

Example: Creating an EC2 Instance

Hereโ€™s an example of a resource block to create an EC2 instance:

resource "aws_instance" "my_ec2_instance" {
  ami           = "ami-0abcdef1234567890"
  instance_type = "t2.micro"
  tags = {
    Name = "MyFirstInstance"
  }
}

Explanation:

  1. resource "aws_instance" "my_ec2_instance":

    • The resource type is aws_instance (used to create EC2 instances).

    • The local name is my_ec2_instance (user-defined and unique within the module).

  2. Arguments:

    • ami: Specifies the Amazon Machine Image (AMI) ID for the instance.

    • instance_type: Defines the instance size (e.g., t2.micro).

    • tags: Adds metadata for the resource.

Understanding Resource Types and Arguments

Each resource block is linked to a specific resource type, which:

  • Determines the type of infrastructure object it manages.

  • Defines the available arguments and attributes.

For example:

  • aws_instance supports arguments like ami, instance_type, availability_zone, and more.

  • aws_vpc supports arguments like cidr_block, enable_dns_support, and others.

You can find a complete list of arguments for each resource type in the Terraform Registry.

Best Practices for Resource Blocks

  1. Uniqueness:

    • Each resource block must have a unique local name within the module.

    • For example, you cannot have two aws_instance blocks with the same local name (my_ec2_instance).

  2. Referencing Resources:

    • You can reference resources in other parts of your configuration using the combination of resource type and local name.

    • Example: Access the public IP of the instance:

        aws_instance.my_ec2_instance.public_ip

  3. Documentation:

    • Always refer to the Terraform Registry for detailed documentation on resource types and arguments.

    • Example: AWS Instance Documentation

Using Resource Arguments

Arguments within the resource block define the resource's configuration. For instance:

  • ami: The ID of the Amazon Machine Image to use.

  • instance_type: Specifies the instance size.

  • tags: Adds metadata to the resource for better identification.

Each resource type has its specific set of arguments, which cannot be used interchangeably. For example:

  • ami is valid for aws_instance but not for aws_vpc.

  • Arguments for a database resource are different from those for a compute instance.

Finding Resource Types and Arguments

To find the correct resource type and arguments:

  1. Visit the Terraform Registry.

  2. Search for the resource type (e.g., aws_instance for EC2).

  3. Review the detailed documentation, which includes all available arguments and attributes.

Conclusion

Terraform resources are the foundation of your infrastructure as code (IaC). They:

  • Define the specific infrastructure components you want to create.

  • Allow for detailed control through arguments specific to each resource type.

  • Provide flexibility to manage complex infrastructure efficiently.

Understanding the structure and purpose of resource blocks is essential for working effectively with Terraform. In the next section, weโ€™ll explore how to write complete Terraform scripts using providers and resources to build a robust infrastructure.

Stay tuned! ๐Ÿš€

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