UPGRADE-GUIDE-3.0.md

Changes from 2.x to 3.x

• IPAM vpcs no longer rely on the aws_vpc_ipam_preview_next_cidr resource. This is a breaking change for VPCs were built with this resource dependency, with a workaround available. Removing this dependency was the last major [known] sore thumb of this module. With this removed we can now build vpcs in the same module as IPAMs, or, more importantly, prefix lists / transit gateways in the same apply as the vpc.
• transit gateway id is now passed as a root level variable. Previously it was passed in var.subnets.transit_gateway.transit_gateway_id. While this was logically a nice way to organize variable references it lead to race conditions if you were trying to create a transit gateway in the same root module as the VPC call.
• route to transit gateway is now passed at a root level via variable transit_gateway_routes. Previously it was passed in var.subnets..route_to_transit_gateway. While this was logically a nice way to organize variable references it lead to race conditions if you were trying to create the prefix list in the same root module as the VPC call.

Required Changes to Make

Regarding changes to Transit Gateway users

Before:

module "vpc" {
  ...
  subnets = {
    transit_gateway = {
      transit_gateway_id = <>
      ...
    }
  }
}

After:

module "vpc" {
  ...
  transit_gateway_id = <>
  subnets = {...}
}

Regarding changes to Transit Gateway Routes using prefix list

Before:

module "vpc" {
  ...
  subnets = {
    public = {
      route_to_transit_gateway = <prefix-list-id>
    }
    private = {
      route_to_transit_gateway = <prefix-list-id>
    }
  }
}

After:

module "vpc" {
  ...
  transit_gateway_id = <>
  transit_gateway_routes = {
    public = <prefix-list-id>
    private   = <prefix-list-id>
  }
  subnets = {...}
}

Regarding changes to IPAM users

Using you were using the IPAM Example and you upgrde to v3, you must make the following changes to avoid a re-build.

1. Upgrade the module terraform init -upgrade
2. Remove the preview resource from the state file: terraform state rm 'module.vpc.aws_vpc_ipam_preview_next_cidr.main[0]'
3. Make necessary HCL changes

HCL changes

Before:

module "vpc" {
  name     = "ipam-vpc"
  az_count = 3

  vpc_ipv4_ipam_pool_id   = "ipam-pool-079f76df39be519c9"
  vpc_ipv4_netmask_length = 26

  subnets = {
    private = {
      netmask                 = 28
      connect_to_public_natgw = false
    }
  }
}

After :

Commenting out lines that can be removed for clarity. Feel free to remove from your module reference

module "vpc" {
  name     = "ipam-vpc"
  az_count = 3

  vpc_ipv4_ipam_pool_id   = "ipam-pool-079f76df39be519c9"
  # vpc_ipv4_netmask_length = 26
  cidr_block = "172.2.0.192/26"

  subnets = {
    private = {
      cidrs = ["172.2.0.192/28", "172.2.0.208/28", "172.2.0.224/28"]
      # netmask                 = 28
      connect_to_public_natgw = false
    }
  }
}

Previous upgrade guides

• v2 Upgrade