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Merge pull request #29 from gruntwork-io/instance-type
Add instance-type module to help deal with t2.micro / t3.micro issue
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‎.circleci/config.yml

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curl -Ls https://raw.githubusercontent.com/gruntwork-io/gruntwork-installer/master/bootstrap-gruntwork-installer.sh | bash /dev/stdin --version v0.0.21
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gruntwork-install --module-name "gruntwork-module-circleci-helpers" --repo "https://github.com/gruntwork-io/module-ci" --tag "v0.13.3"
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gruntwork-install --binary-name "terratest_log_parser" --repo "https://github.com/gruntwork-io/terratest" --tag "v0.13.20"
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configure-environment-for-gruntwork-module --circle-ci-2 --use-go-dep --go-src-path test --terragrunt-version NONE --terraform-version 0.12.0
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configure-environment-for-gruntwork-module --circle-ci-2 --use-go-dep --go-src-path test --terragrunt-version NONE --terraform-version 0.12.28
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2020
- run:
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name: run tests (with python2)

‎examples/instance-type/README.md

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# Instance types example
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This folder shows examples of how to use the [instance-type module](/modules/instance-type) to pick an instance type
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that's available in all Availability Zones in the current AWS region.
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## How do you run these examples?
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1. Install [Terraform](https://www.terraform.io/).
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1. `terraform init`.
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1. `terraform apply`.
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‎examples/instance-type/main.tf

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provider "aws" {
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region = var.aws_region
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}
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# ----------------------------------------------------------------------------------------------------------------------
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# FIGURE OUT WHAT INSTANCE TYPE IS AVAILABLE IN ALL AZS IN THE CURRENT AWS REGION
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# ----------------------------------------------------------------------------------------------------------------------
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module "instance_types" {
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source = "../../modules/instance-type"
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instance_types = var.instance_types
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}
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# ----------------------------------------------------------------------------------------------------------------------
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# USE THAT INSTANCE TYPE TO LAUNCH AN EC2 INSTANCE
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# ----------------------------------------------------------------------------------------------------------------------
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resource "aws_instance" "example" {
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ami = data.aws_ami.ubuntu.id
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instance_type = module.instance_types.recommended_instance_type
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tags = {
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Name = "instance-type-example"
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}
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}
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# ----------------------------------------------------------------------------------------------------------------------
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# FETCH THE ID OF AN UBUNTU AMI IN THE CURRENT REGION
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# ----------------------------------------------------------------------------------------------------------------------
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data "aws_ami" "ubuntu" {
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most_recent = true
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owners = ["099720109477"] # Canonical
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filter {
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name = "virtualization-type"
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values = ["hvm"]
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}
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filter {
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name = "architecture"
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values = ["x86_64"]
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}
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filter {
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name = "image-type"
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values = ["machine"]
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}
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filter {
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name = "name"
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values = ["ubuntu/images/hvm-ssd/ubuntu-xenial-16.04-amd64-server-*"]
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}
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}

‎examples/instance-type/outputs.tf

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output "instance_type_map" {
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description = "A map where the keys are the instance types in var.instance_types and the values are true or false, depending on whether every AZ in the current region contains this instance type."
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value = module.instance_types.instance_type_map
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}
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output "recommended_instance_type" {
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description = "The recommended instance type to use in this AWS region. This will be the first instance type in var.instance_types which is available in all AZs in this region."
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value = module.instance_types.recommended_instance_type
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}

‎examples/instance-type/variables.tf

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variable "aws_region" {
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description = "The AWS region to run this code in"
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type = string
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default = "eu-west-1"
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}
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variable "instance_types" {
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description = "A list of instance types to look up in the current AWS region."
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type = list(string)
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default = ["t3.micro", "t2.micro"]
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}

‎modules/instance-type/README.md

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# Instance Type
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This is a module that can be used to look up a list of EC2 instance types and determine which of them is available in
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all Availability Zones (AZs) in the current AWS Region. This is useful because certain instance types, such as
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`t2.micro` are not available in some of the newer AZs, while `t3.micro` is not available in some of the older AZs, and
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if you have code that needs to run on a "small" instance across all AZs in many different regions, you can use this
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module to automatically figure out which instance type you should use.
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## Example code
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See the [instance-type example](/examples/instance-type) for working sample code.
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## Usage
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Use the module in your Terraform code, replacing `<VERSION>` with the latest version from the [releases
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page](https://github.com/gruntwork-io/package-terraform-utilities/releases):
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```hcl
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module "path" {
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source = "git::[email protected]:gruntwork-io/package-terraform-utilities.git//modules/instance-type?ref=<VERSION>"
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instance_types = ["t2.micro", "t3.micro"]
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}
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```
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The arguments to pass are:
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* `instance_types`: A list of instance types to look up in the current AWS region. We recommend putting them in order
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of preference, as the recommended_instance_type output variable will contain the first instance type from this list
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that is available in all AZs.
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When you run `apply`, the `recommended_instance_type` output variable will contain the recommended instance type to
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use. This will be the first instance type from your `instance_types` input that is available in all AZs in the current
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region. If no instance type is available in all AZs, you'll get an error.
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For example, as of July, 2020, if you run `apply` on the code above in `eu-west-1`, the `recommended_instance_type`
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will be `t2.micro`, as that's available in all AZs in `eu-west-1`. However, if you run the same code in
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`ap-northeast-2`, the `recommended_instance_type` will be `t3.micro`, as `t2.micro` is only available in 2 of the 4 AZs.

‎modules/instance-type/main.tf

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data "aws_ec2_instance_type_offerings" "offerings" {
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for_each = toset(data.aws_availability_zones.available.names)
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filter {
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name = "instance-type"
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values = var.instance_types
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}
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filter {
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name = "location"
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values = [each.key]
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}
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location_type = "availability-zone"
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}
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data "aws_availability_zones" "available" {
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state = "available"
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}

‎modules/instance-type/outputs.tf

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locals {
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instance_type_map = { for instance_type in var.instance_types : instance_type => (
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! contains([for az, offerings in data.aws_ec2_instance_type_offerings.offerings : contains(offerings.instance_types, instance_type)], false))
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}
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recommended_instance_type = [for instance_type in var.instance_types : instance_type if local.instance_type_map[instance_type]][0]
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}
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output "instance_type_map" {
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description = "A map where the keys are the instance types in var.instance_types and the values are true or false, depending on whether every AZ in the current region contains this instance type."
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value = local.instance_type_map
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}
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output "recommended_instance_type" {
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description = "The recommended instance type to use in this AWS region. This will be the first instance type in var.instance_types which is available in all AZs in this region."
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value = local.recommended_instance_type
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}

‎modules/instance-type/variables.tf

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variable "instance_types" {
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description = "A list of instance types to look up in the current AWS region. We recommend putting them in order of preference, as the recommended_instance_type output variable will contain the first instance type from this list that is available in all AZs."
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type = list(string)
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}

‎test/instance_type_test.go

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package test
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import (
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"github.com/gruntwork-io/terratest/modules/aws"
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"github.com/gruntwork-io/terratest/modules/terraform"
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"testing"
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)
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func TestInstanceType(t *testing.T) {
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t.Parallel()
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awsRegion := aws.GetRandomRegion(t, nil, nil)
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terratestOptions := &terraform.Options{
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TerraformDir: "../examples/instance-type",
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Vars: map[string]interface{}{
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"aws_region": awsRegion,
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},
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}
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defer terraform.Destroy(t, terratestOptions)
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// We only need to run 'apply' for this test. If the instance launches successfully, it's because the code picked
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// the right instance type to use for the current region (note: we pick the region at random).
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terraform.InitAndApply(t, terratestOptions)
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}

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