Assigning an elastic IP to a aws instance and no instance public IP

Terraform
1

Hi,

I want to assign a single static public ip to an aws instance, using an elastic IP as its own public IP, but I’m seeing some weird behavior that I do not understand why it happens. I create the eip like this:

resource "aws_eip" "eip_manager" {
  instance   = aws_instance.manager.*.id[count.index]
  vpc = true
}

And the aws_resource:

resource "aws_instance" "manager" {
  count                        = var.manager_count
  ami                          = var.manager_ami
  instance_type                = var.manager_instance_type
  iam_instance_profile         = aws_iam_instance_profile.ec2-storage-instance-profile.name
  key_name                     = aws_key_pair.default.id
  user_data                    = file(var.bootstrap_path)
  vpc_security_group_ids       = [aws_security_group.swarm.id]
  subnet_id                    = element(tolist(data.aws_subnet_ids.subnet.ids), count.index)

  root_block_device {
    volume_size           = var.manager_disk_size
    volume_type           = var.manager_disk_type
    delete_on_termination = "true"
  }

  connection {
    type     = "ssh"
    user     = var.ssh_user
    private_key = file(var.private_key_default)
    host     = self.public_ip
  }
}

After running terraform appy the instance is assigned two public IP addresses as expected, one to the instance and the eip. But if I run terraform apply again (with no code changes) the instance public IP address is replaced with the eip address, leaving the instance with only one public IP. Why is this ??

And if I add associate_public_ip_address = false to the instance resource then only the eip address is assigned as expected, but again, if I run again terraform apply the instance is proposed to be deleted and recreated. Why is this ?

How should I create an aws instance with only the eip address and avoid that behavior ?

Tested with both terraform 0.12.x and 0.13beta.

Thanks.