How do you specify a VPC within a aws_elb resource definition?

[Henry Franco]

I've looked over aws_elb Terraform without any luck. I don't have a default VPC defined and I can't list a VPC in the aws_elb resource. How do I specify a VPC within my aws_elb resource? I'm getting the following error:

Error: Error applying plan:


1 error(s) occurred:


* module.rtr_nexus.aws_elb.my_elb: 1 error(s) occurred:


* aws_elb.nexus_elb: InvalidConfigurationRequest: Default VPC not found
 status code: 409, request id: 7ad595ce-dba3-11e8-88ba-c3211a9a6526

Here's what my code looks like.

resource "aws_elb" "my_elb" {
  name                    = "terraform-asg"
  availability_zones      = ["${data.aws_availability_zones.all.names}"]
  security_groups         = ["${aws_security_group.elb.id}"]

  listener {
    lb_port               = 80
    lb_protocol           = "http"
    instance_port         = "${var.elb_server_port}"
    instance_protocol     = "http"
  }


  health_check {
    healthy_threshold     = 2
    unhealthy_threshold   = 2
    timeout               = 3
    interval              = 30
    target                = "HTTP:${var.elb_server_port}/"
  }
}

[David Adams]

You have to specify the subnets (one per AZ) that you want to use, using the `subnets` property. How you get the list of subnets depends on a lot of things. We typically have one public and one private subnet per AZ that we're using in each VPC. And so an Internet facing ELB would need to be in the public subnets. We tag our public subnets with `Visibility=Public`. So then we use essentially this code to get our list of public subnets for a VPC:

    data "aws_subnet_ids" "public" {

      vpc_id = "${var.vpc_id}"

      tags   = { Visibility = "Public" }

    }

And then you can just dump those into your ELB:

    resource "aws_elb" "example" {

      subnets = ["${data.aws_subnet_ids.public.ids}"]

      #...

    }

This _does_ depend on tagging discipline etc. So you may prefer to just hardcode a list of subnet IDs, or use some other method to look them up.

-dave

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[Henry Franco]

David, that actually makes sense. I made the necessary adjustments using the code snippets you provided and it appears the subnet IDs and availability zones aren't matching?

Here's the error I'm getting:

Error: Error applying plan:


1 error(s) occurred:

* aws_elb.nexus_elb: 1 error(s) occurred:


* aws_elb.my_elb: ValidationError: Only one of SubnetIds or AvailabilityZones may be specified
 status code: 400, request id: 8af03d68-dbaf-11e8-8e30-f1e0485f6068

Here's what my code now looks like. I also changed the tags to make the filter work:

resource "aws_elb" "my_elb" {
  name                  = "terraform-asg-example"
  availability_zones    = ["${data.aws_availability_zones.all.names}"]
  subnets               = ["${data.aws_subnet_ids.public.ids}"]

  listener {
    lb_port             = "80"
    lb_protocol         = "http"

    instance_port       = "80"

    instance_protocol   = "http"
  }

  health_check {
    healthy_threshold   = 2
    unhealthy_threshold = 2
    timeout             = 3
    interval            = 30

    target              = "HTTP:80/"
  }
}


data "aws_availability_zones" "all" {}

data "aws_subnet_ids" "public" {
  vpc_id                = "${var.vpc_id}"
  tags                  = { Visibility = "Public" }
}

[Ryan Hartkopf]

Hi Henry,

Only one of SubnetIds or AvailabilityZones may be specified

Now that you're specifying the subnet IDs, the availability zones will be inferred from the subnet IDs provided. Try removing the `availability_zones` argument and planning again.