How do you launch an instance with EIP straight away? - amazon-web-services

Question

Having trouble with attaching eip to ec2 instance. I can only do it be assigning public ip then after instance is built then attaching eip. I want to add the EIP before the instance builds.
resource "aws_instance" "third-WG" {
provider = aws.third
ami = data.aws_ami.ubuntu3.id
instance_type = "t2.micro"
key_name = aws_key_pair.third_WGkey.key_name
associate_public_ip_address = true
private_ip = "10.3.0.10"
subnet_id = aws_subnet.third-WG-Subnet.id
vpc_security_group_ids = [aws_security_group.third-SG.id]
depends_on = [aws_instance.WG_DL_SRV]
}
resource "aws_eip" "third_WG_EIP" {
provider = aws.third
vpc = true
instance = aws_instance.third-WG.id
depends_on = [aws_internet_gateway.third-IGW]
provisioner "local-exec" {
command = "echo ${aws_eip.third_WG_EIP.public_ip} > ~/Desktop/whole-
wash/var/3rd_PUB_IP.txt"
}
tags = {
Name = "third_WG_EIP"
}
}

Answer 1

Instead of attaching the Elastic IP to the instance, which makes the instance a dependency of the Elastic IP forcing it to be built first, you can instead create a network interface, and attach the Elastic IP to that. You then also make that interface used by the instance, and so everything is then brought up together.
resource "aws_network_interface" "nic" {
private_ips = ["10.3.0.10"]
subnet_id = aws_subnet.third-WG-Subnet.id
#Todo: populate any other needed NIC parameters
}
resource "aws_eip" "third_WG_EIP" {
provider = aws.third
vpc = true
network_interface = aws_network_interface.nic
depends_on = [aws_internet_gateway.third-IGW]
provisioner "local-exec" {
command = "echo ${aws_eip.third_WG_EIP.public_ip} > ~/Desktop/whole-
wash/var/3rd_PUB_IP.txt"
}
tags = {
Name = "third_WG_EIP"
}
}
resource "aws_instance" "third-WG" {
provider = aws.third
ami = data.aws_ami.ubuntu3.id
instance_type = "t2.micro"
key_name = aws_key_pair.third_WGkey.key_name
associate_public_ip_address = true
vpc_security_group_ids = [aws_security_group.third-SG.id]
depends_on = [aws_instance.WG_DL_SRV]
network_interface {
network_interface_id = aws_network_interface.nic.id
device_index = 0
}
}
If you find it's still in slightly the wrong order, you can also then add the EIP to the depends_on parameter of the instance, since the EIP is no longer dependent on the instance itself.
Note that it's been a while since I've done precisely this, you may find you need to move a few of the other networky type parameters (security groups etc) out of the instance and into the network interface block.