Count variable with EBS, EC2 and Volume Attachments

[ask.ar...@gmail.com]

Terraform v. 0.9.11

I have two directories one for EBS and other for EC2. I run terraform apply for EBS and then I go and give apply for EC2.
I have main.tf and outputs.tf in EBS as follows:

main.tf
resource "aws_ebs_volume" "myapp-ebs" {
    availability_zone = "${element(var.availability_zones, 0)}"
    size = 100
    type = "gp2"
    count = 2
    tags {
        Name = "${var.environment}-elasticsearch01"
    }
}

outputs.tf
output "app_ebs_1" {
    value = "${aws_ebs_volume.myapp-ebs.0.id}"
}
output "app_ebs_2" {
    value = "${aws_ebs_volume.myapp-ebs.1.id}"
}

This works perfectly well and gives me volume ID of two EBS created.
This is my main.tf file for EC2 instance.

main.tf

/* Fetch Volume IDs from EBS module for use in here */
data "terraform_remote_state" "ebs_data" {
  backend = "local"

  config {
    path = "${path.module}/../ebs/terraform.tfstate"
  }
}

resource "aws_instance" "app-box" {
  ami = "${lookup(var.ami_linux, var.region)}"
  instance_type = "${element(var.instance_types, 5)}"
  subnet_id = "${element(var.subnet_ids, 0)}"
  security_groups = ["${aws_security_group.kafka-security-group.id}"]
  count = 2
  key_name = "${var.key_name}"
  private_ip = "${element(var.kafka-ips, count.index)}"
  iam_instance_profile = "${data.terraform_remote_state.iam_data.iam_profile_out}"
  user_data = "${file("bootstrap_app.sh")}
  tags {
    Name = "${var.environment}-app0${count.index + 1}"
  }
}

/* Attaching EBS Volumes to App instances */
resource "aws_volume_attachment" "a-app_ebs1" {
  device_name  = "/dev/xvdf"
  volume_id    = "${data.terraform_remote_state.ebs_data.app_ebs_1}"
  instance_id  = "${aws_instance.app-box.0.id}"
  force_detach = true
}

resource "aws_volume_attachment" "a-app_ebs2" {
  device_name  = "/dev/xvdf"
  volume_id    = "${data.terraform_remote_state.ebs_data.app_ebs_2}"
  instance_id  = "${aws_instance.app-box.1.id}"
  force_detach = true
}

Now the problem here is, 2 EC2 instances get created but the Volume attachment fails for the second instance. Plan and apply both fails with the following error:

* aws_volume_attachment.a-app_ebs2: Resource 'aws_instance.app-box' not found for variable 'aws_instance.app-box.1.id'

Not sure what mistake I am making here. Any improvements I can do to avoid this issue? Help much appreciated. I have to push this urgently for everyday use.