TF_Utility-InstanceTypeAvailabilityChecker_Public

Description Details:

This repository provides a Terraform utility to check the availability of instance types in specific AWS regions. From verifying compatibility in availability zones to generating detailed lists, optimize your deployment decisions.

Terraform Small Utility Project

Step-01: Introduction

Current Problem:

• We are not able to create EC2 Instances in all the subnets of our VPC which are spread across all availability zones in that region

Approach to a Solution:

• We need to find a solution to say that our desired EC2 Instance Type example: t3.micro is supported in that availability zone or not
• In simple terms, give me the availability zone list in a particular region where by desired EC2 Instance Type (t3.micro) is supported

Why utility project?

• In Terraform, we should not go and try things directly in large code base.
• First try your requirements in small chunks and integrate that to main code base.
• We are going to do the same now.

Step-02: c1-versions.tf

• Hard-coded the region as we are not going to use any variables.tf in this utility project

# Provider Block
provider "aws" {
  region  = "us-east-1"
}

Step-03: c2-v1-get-instancetype-supported-per-az-in-a-region.tf

• We are first going to explore the datasource and it outputs

# Determine which Availability Zones support your instance type
aws ec2 describe-instance-type-offerings --location-type availability-zone  --filters Name=instance-type,Values=t3.micro --region us-east-1 --output table

Step-03-01: Review / Create the datasource and its output

# Datasource
data "aws_ec2_instance_type_offerings" "my_ins_type1" {
  filter {
    name   = "instance-type"
    values = ["t3.micro"]
  }
  filter {
    name   = "location"
    values = ["us-east-1a"]
    #values = ["us-east-1e"]    
  }
  location_type = "availability-zone"
}


# Output
output "output_v1_1" {
 value = data.aws_ec2_instance_type_offerings.my_ins_type1.instance_types
}

Step-03-02: Execute Terraform Commands

# Terraform Initialize
terraform init

# Terraform Validate
terraform validate

# Terraform Plan
terraform plan
terraform apply -auto-approve
Observation: 
1. Output should have the instance value `t3.micro` when `values = ["us-east-1a"]` in location filter
# Sample Output
output_v1_1 = toset([
  "t3.micro",
])

# Make a change
Switch the values in `location` filter to `values = ["us-east-1e"]` and test again with `terraform plan`

# Terraform Plan
terraform plan
terraform apply -auto-approve
Observation: 
1. Output should have the instance value empty `[]` when `values = ["us-east-1e"]` in location filter
# Sample Output
output_v1_1 = toset([])

Step-04: c2-v2-get-instancetype-supported-per-az-in-a-region.tf

• Using for_each create multiple instances of datasource and loop it with hard-coded availability zones in for_each

Step-04-01: Review / Create the datasource and its output with for_each

# Check if that respective Instance Type is supported in that Specific Region in list of availability Zones
# Get the List of Availability Zones in a Particular region where that respective Instance Type is supported
data "aws_ec2_instance_type_offerings" "my_ins_type2" {
  for_each = toset([ "us-east-1a", "us-east-1e" ])
  filter {
    name   = "instance-type"
    values = ["t3.micro"]
  }
  filter {
    name   = "location"
    values = [each.key]
  }
  location_type = "availability-zone"
}


# Important Note: Once for_each is set, its attributes must be accessed on specific instances
output "output_v2_1" {
 #value = data.aws_ec2_instance_type_offerings.my_ins_type1.instance_types
 value = toset([
      for t in data.aws_ec2_instance_type_offerings.my_ins_type2 : t.instance_types
    ])  
}

# Create a Map with Key as Availability Zone and value as Instance Type supported
output "output_v2_2" {
 value = { for az, details in data.aws_ec2_instance_type_offerings.my_ins_type2 :
  az => details.instance_types }   
}

Step-04-02: Execute Terraform Commands

# Terraform Plan
terraform plan
terraform apply -auto-approve
Observation: refer sample output
# Sample Output
output_v2_1 = toset([
  toset([
    "t3.micro",
  ]),
  toset([]),
])
output_v2_2 = {
  "us-east-1a" = toset([
    "t3.micro",
  ])
  "us-east-1e" = toset([])
}

Step-05: c2-v3-get-instancetype-supported-per-az-in-a-region.tf

Step-05-01: Add new datasource aws_availability_zones

• Get List of Availability Zones in a Specific Region

# Get List of Availability Zones in a Specific Region
# Region is set in c1-versions.tf in Provider Block
data "aws_availability_zones" "my_azones" {
  filter {
    name   = "opt-in-status"
    values = ["opt-in-not-required"]
  }
}

Step-05-02: Update for_each with new datasource

# Check if that respective Instance Type is supported in that Specific Region in list of availability Zones
# Get the List of Availability Zones in a Particular region where that respective Instance Type is supported
data "aws_ec2_instance_type_offerings" "my_ins_type" {
for_each=toset(data.aws_availability_zones.my_azones.names)
  filter {
    name   = "instance-type"
    values = ["t3.micro"]
  }
  filter {
    name   = "location"
    values = [each.key]
  }
  location_type = "availability-zone"
}

Step-05-03: Implement Incremental Outputs till we reach what is required

# Basic Output: All Availability Zones mapped to Supported Instance Types
output "output_v3_1" {
 value = { for az, details in data.aws_ec2_instance_type_offerings.my_ins_type :
  az => details.instance_types }   
}

# Filtered Output: Exclude Unsupported Availability Zones
output "output_v3_2" {
  value = { for az, details in data.aws_ec2_instance_type_offerings.my_ins_type :
  az => details.instance_types if length(details.instance_types) != 0 }
}

# Filtered Output: with Keys Function - Which gets keys from a Map
# This will return the list of availability zones supported for a instance type
output "output_v3_3" {
  value = keys({ for az, details in data.aws_ec2_instance_type_offerings.my_ins_type :
  az => details.instance_types if length(details.instance_types) != 0 }) 
}

# Filtered Output: As the output is list now, get the first item from list (just for learning)
output "output_v3_4" {
  value = keys({ for az, details in data.aws_ec2_instance_type_offerings.my_ins_type :
  az => details.instance_types if length(details.instance_types) != 0 })[0]
}

Step-05-04: Execute Terraform Commands

# Terraform Plan
terraform plan
terraform appy -auto-approve
Observation: refer sample output
1. In the final output you will only get the availability zones list in which `t3.micro` instance is supported
# Sample Output
output_v3_1 = {
  "us-east-1a" = toset([
    "t3.micro",
  ])
  "us-east-1b" = toset([
    "t3.micro",
  ])
  "us-east-1c" = toset([
    "t3.micro",
  ])
  "us-east-1d" = toset([
    "t3.micro",
  ])
  "us-east-1e" = toset([])
  "us-east-1f" = toset([
    "t3.micro",
  ])
}
output_v3_2 = {
  "us-east-1a" = toset([
    "t3.micro",
  ])
  "us-east-1b" = toset([
    "t3.micro",
  ])
  "us-east-1c" = toset([
    "t3.micro",
  ])
  "us-east-1d" = toset([
    "t3.micro",
  ])
  "us-east-1f" = toset([
    "t3.micro",
  ])
}
output_v3_3 = [
  "us-east-1a",
  "us-east-1b",
  "us-east-1c",
  "us-east-1d",
  "us-east-1f",
]
output_v3_4 = "us-east-1a"

Step-06: Clean-Up

# Terraform Destroy
terraform destroy -auto-approve

# Delete Files
rm -rf .terraform*
rm -rf terraform.tfstate*