Terraform multiple for_each resources

Question

I've created multiple subnets and multiple VPC endpoints using the for_each loop as follows:

### VARIABLES ###

variable "private_cidr_mask" {
  default = {
    "us-west-1a" = "10.0.1.0/24"
    "us-west-1b" = "10.0.2.0/24"
  }
}

variable "vpc_endpoints" {
  default = [
    "com.amazonaws.us-west-1.ecs-agent",
    "com.amazonaws.us-west-1.ecs-telemetry",
    "com.amazonaws.us-west-1.ecs"
  ]
}

### RESOURCES ###

resource "aws_subnet" "private_subnet" {

  for_each = var.private_cidr_mask

  vpc_id = aws_vpc.vpc.id
  availability_zone = each.key
  cidr_block = each.value
}

resource "aws_vpc_endpoint" "vpc_endpoint" {

  for_each = toset(var.vpc_endpoints)

  vpc_id = aws_vpc.vpc.id
  vpc_endpoint_type = "Interface"
  service_name = each.value

  security_group_ids = [ aws_security_group.security_group.id ]

  private_dns_enabled = true
}

Now I have to assign every VPC endpoint to each of the private subnets using a aws_vpc_endpoint_subnet_association:

resource "aws_vpc_endpoint_subnet_association" "vpc_endpoint_subnet_association" {
  vpc_endpoint_id = <every endpoint>
  subnet_id = <every subnet>
}

How do I achieve this in Terraform? I have tried nested for_each loops without success.

Solution

It turns out that aws_vpc_endpoint accepts a list of subnet_ids and I just missed it in the docs, so all I had to do was:

resource "aws_vpc_endpoint" "vpc_endpoint" {

  for_each = toset(var.vpc_endpoints)

  vpc_id = aws_vpc.vpc.id
  vpc_endpoint_type = "Interface"
  service_name = each.value

  security_group_ids = [ aws_security_group.security_group.id ]
  subnet_ids = [ for subnet in aws_subnet.private_subnet: subnet.id ]

  private_dns_enabled = true
}

Comments

[Martin Atkins]

The example at terraform.io/docs/configuration/functions/… might give some useful pointers