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Refactor route table module #1

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936c978
Decouple associations from propagations
ronaldour Feb 25, 2025
39759aa
Update docs
ronaldour Feb 25, 2025
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27 changes: 15 additions & 12 deletions modules/route-table/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -20,18 +20,20 @@ module "transit_gateway_route_table" {
name = "example"
transit_gateway_id = module.transit_gateway.id

associations = {
vpc1 = {
associations = [
{
transit_gateway_attachment_id = module.transit_gateway.vpc_attachments["vpc1"].id
propagate_route_table = true
}
vpc2 = {
replace_existing_association = true
},
{
transit_gateway_attachment_id = module.transit_gateway.vpc_attachments["vpc2"].id
propagate_route_table = true
}
}
},
]

propagations = [ module.transit_gateway.vpc_attachments["vpc1"].id, module.transit_gateway.vpc_attachments["vpc2"].id ]


routes = {
static_routes = {
blackhole = {
blackhole = true
destination_cidr_block = "0.0.0.0/0"
Expand Down Expand Up @@ -93,12 +95,13 @@ No modules.

| Name | Description | Type | Default | Required |
|------|-------------|------|---------|:--------:|
| <a name="input_associations"></a> [associations](#input\_associations) | A map of transit gateway attachment IDs to associate with the Transit Gateway route table | <pre>map(object({<br/> transit_gateway_attachment_id = optional(string)<br/> replace_existing_association = optional(bool)<br/> propagate_route_table = optional(bool, false)<br/> }))</pre> | `{}` | no |
| <a name="input_associations"></a> [associations](#input\_associations) | List of Transit Gateway Attachments ids to associate to the route table | <pre>list(object({<br/> transit_gateway_attachment_id = string<br/> replace_existing_association = optional(bool)<br/> }))</pre> | `[]` | no |
| <a name="input_create"></a> [create](#input\_create) | Controls if resources should be created (it affects almost all resources) | `bool` | `true` | no |
| <a name="input_name"></a> [name](#input\_name) | Name to be used on all the resources as identifier | `string` | `""` | no |
| <a name="input_routes"></a> [routes](#input\_routes) | A map of Transit Gateway routes to create in the route table | <pre>map(object({<br/> destination_cidr_block = string<br/> blackhole = optional(bool, false)<br/> transit_gateway_attachment_id = optional(string)<br/> }))</pre> | `{}` | no |
| <a name="input_propagations"></a> [propagations](#input\_propagations) | List of Transit Gateway Attachments ids to propagate to the route table | `list(string)` | `[]` | no |
| <a name="input_static_routes"></a> [static\_routes](#input\_static\_routes) | A map of Transit Gateway routes to create in the route table | <pre>list(object({<br/> destination_cidr_block = string<br/> blackhole = optional(bool, false)<br/> transit_gateway_attachment_id = optional(string)<br/> }))</pre> | `[]` | no |
| <a name="input_tags"></a> [tags](#input\_tags) | A map of tags to add to all resources | `map(string)` | `{}` | no |
| <a name="input_transit_gateway_id"></a> [transit\_gateway\_id](#input\_transit\_gateway\_id) | The ID of the EC2 Transit Gateway | `string` | `""` | no |
| <a name="input_transit_gateway_id"></a> [transit\_gateway\_id](#input\_transit\_gateway\_id) | The ID of the EC2 Transit Gateway for the route table | `string` | n/a | yes |
| <a name="input_vpc_routes"></a> [vpc\_routes](#input\_vpc\_routes) | A map of VPC routes to create in the route table provided | <pre>map(object({<br/> route_table_id = string<br/> destination_cidr_block = optional(string)<br/> destination_ipv6_cidr_block = optional(string)<br/> }))</pre> | `{}` | no |

## Outputs
Expand Down
8 changes: 4 additions & 4 deletions modules/route-table/main.tf
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Expand Up @@ -14,17 +14,17 @@ resource "aws_ec2_transit_gateway_route_table" "this" {
}

resource "aws_ec2_transit_gateway_route_table_association" "this" {
for_each = { for k, v in var.associations : k => v if var.create }
for_each = { for a in var.associations : a.transit_gateway_attachment_id => a if var.create }

transit_gateway_attachment_id = each.value.transit_gateway_attachment_id
transit_gateway_route_table_id = aws_ec2_transit_gateway_route_table.this[0].id
replace_existing_association = try(each.value.replace_existing_association, null)
}

resource "aws_ec2_transit_gateway_route_table_propagation" "this" {
for_each = { for k, v in var.associations : k => v if var.create && try(v.propagate_route_table, false) }
for_each = { for p in var.propagations : p => p if var.create }

transit_gateway_attachment_id = each.value.transit_gateway_attachment_id
transit_gateway_attachment_id = each.value
transit_gateway_route_table_id = aws_ec2_transit_gateway_route_table.this[0].id
}

Expand All @@ -33,7 +33,7 @@ resource "aws_ec2_transit_gateway_route_table_propagation" "this" {
################################################################################

resource "aws_ec2_transit_gateway_route" "this" {
for_each = { for k, v in var.routes : k => v if var.create }
for_each = { for route in var.static_routes : route.destination_cidr_block => route if var.create }
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@ronaldour ronaldour Mar 7, 2025

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We still use for_each to prevent changes, it's just the parameter that it's a list instead of a map. We use the destination_cidr_block as the key (it's a good candidate because duplicated cidrs are not allowed in the routes).

I think this simplifies using the module but if that's not a good Terraform practice we can stick with maps


destination_cidr_block = each.value.destination_cidr_block
blackhole = each.value.blackhole
Expand Down
24 changes: 14 additions & 10 deletions modules/route-table/variables.tf
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Expand Up @@ -21,33 +21,37 @@ variable "tags" {
################################################################################

variable "transit_gateway_id" {
description = "The ID of the EC2 Transit Gateway"
description = "The ID of the EC2 Transit Gateway for the route table"
type = string
default = ""
}

variable "associations" {
description = "A map of transit gateway attachment IDs to associate with the Transit Gateway route table"
type = map(object({
transit_gateway_attachment_id = optional(string)
description = "List of Transit Gateway Attachments ids to associate to the route table"
type = list(object({
transit_gateway_attachment_id = string
replace_existing_association = optional(bool)
propagate_route_table = optional(bool, false)
}))
default = {}
default = []
}

variable "propagations" {
description = "List of Transit Gateway Attachments ids to propagate to the route table"
type = list(string)
default = []
}

################################################################################
# Route(s)
################################################################################

variable "routes" {
variable "static_routes" {
description = "A map of Transit Gateway routes to create in the route table"
type = map(object({
type = list(object({
destination_cidr_block = string
blackhole = optional(bool, false)
transit_gateway_attachment_id = optional(string)
}))
default = {}
default = []
}

variable "vpc_routes" {
Expand Down