Error registering targets with target group: InvalidTarget: The following targets are not in a running state and cannot be registered

[edeas123]

Terraform Version

Terraform v0.11.11
+ provider.aws v1.54.0

Terraform Configuration Files

resource "aws_alb" "rancher-ctl-host-alb" {
	name = "rancher-ctl-host-alb"
	internal = false
	load_balancer_type = "application"
	ip_address_type  = "ipv4"

	subnets = ["${data.aws_subnet_ids.vpc_subnets.ids}"]
	security_groups = [
		"${data.terraform_remote_state.core.rancher-ctl-host-alb-sg-id}"
	]
}

# create an application load balancer listener 
resource "aws_alb_listener" "rancher-ctl-host-alb-listener" {
	load_balancer_arn = "${aws_alb.rancher-ctl-host-alb.arn}"
	port = 80
	protocol = "HTTP"

	default_action {
    	type             = "forward"
    	target_group_arn = "${aws_alb_target_group.rancher-ctl-host-target-group.arn}"
  	}
}

# create the application load balancer target group
resource "aws_alb_target_group" "rancher-ctl-host-target-group" {
	name = "rancher-ctl-host-target-group"
	port = 8080
	protocol = "HTTP"
	vpc_id = "${data.terraform_remote_state.core.default-vpc-id}"
}

# attach the three hosts to the target group
resource "aws_alb_target_group_attachment" "rancher-ctl-host-target-group-instances" {
  target_group_arn = "${aws_alb_target_group.rancher-ctl-host-target-group.arn}"
  target_id        = "${aws_spot_instance_request.rancher-ctl-host.*.spot_instance_id[count.index]}"
  port             = 8080
  count            = 3
}```

### Expected Behavior
<!--
It should not have given errors applying the plan
-->

### Actual Behavior
<!--
Error: Error applying plan:

3 error(s) occurred:

* aws_alb_target_group_attachment.rancher-ctl-host-target-group-instances[2]: 1 error(s) occurred:

* aws_alb_target_group_attachment.rancher-ctl-host-target-group-instances.2: Error registering targets with target group: InvalidTarget: The following targets are not in a running state and cannot be registered: 'i-0791f6bee8a082a10'
        status code: 400, request id: 990ee63b-3053-11e9-92bd-4d5e8013e613
* aws_alb_target_group_attachment.rancher-ctl-host-target-group-instances[0]: 1 error(s) occurred:

* aws_alb_target_group_attachment.rancher-ctl-host-target-group-instances.0: Error registering targets with target group: InvalidTarget: The following targets are not in a running state and cannot be registered: 'i-0b8c1f6d35f57c5cb'
        status code: 400, request id: 990f0dbc-3053-11e9-bbd2-3b6b83537945
* aws_alb_target_group_attachment.rancher-ctl-host-target-group-instances[1]: 1 error(s) occurred:

* aws_alb_target_group_attachment.rancher-ctl-host-target-group-instances.1: Error registering targets with target group: InvalidTarget: The following targets are not in a running state and cannot be registered: 'i-033d01746af85be03'
        status code: 400, request id: 990f3424-3053-11e9-aa19-bf12dffa0d2b
-->

### Additional Context
<!--
The problem seem to be that the alb_target_group_attachment is created before the spot instances are running (although they have been created), and it does not support interpolation which is needed in my case to use the depends_on.
-->

### References
<!--
- #12634

-->

[ghost]

This issue has been automatically migrated to hashicorp/terraform-provider-aws#7561 because it looks like an issue with that provider. If you believe this is not an issue with the provider, please reply to hashicorp/terraform-provider-aws#7561.

[ghost]

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