Terraform-provider-aws: aws_appautoscaling_target update detaches any aws_appautoscaling_policy's

[hashibot]

_This issue was originally opened by @charlesbjohnson as hashicorp/terraform#8484. It was migrated here as part of the provider split. The original body of the issue is below._

---

Hi there,

Updating an aws_appautoscaling_target (which always forces a new resource) does not trigger dependent aws_appautoscaling_policys to be recreated. As a result, updating min_capacity or max_capacity causes all dependent aws_appautoscaling_policys to be deleted/detached, requiring a subsequent terraform apply to reattach them.

Terraform Version

v0.7.0+

Affected Resource(s)

• aws_appautoscaling_target
• aws_appautoscaling_policy
  

  Terraform Configuration Files

provider "aws" {
  region = "us-west-2"
}

resource "aws_ecs_cluster" "cluster" {
  name = "demo-85e6a168597c3fe593b335df4c11496afe5dea31"
}

resource "aws_ecs_service" "service" {
  name = "${aws_ecs_cluster.cluster.name}"
  cluster = "${aws_ecs_cluster.cluster.id}"
  task_definition = "${aws_ecs_task_definition.task_definition.arn}"
  desired_count = 1
}

resource "aws_ecs_task_definition" "task_definition" {
  family = "nginx"
  container_definitions = <<EOF
[
  {
    "name": "nginx",
    "image": "nginx:latest",
    "cpu": 10,
    "memory": 500,
    "essential": true
  }
]
EOF
}

resource "aws_appautoscaling_target" "target" {
  name = "${aws_ecs_cluster.cluster.name}"
  service_namespace = "ecs"
  resource_id = "service/${aws_ecs_cluster.cluster.name}/${aws_ecs_service.service.name}"
  scalable_dimension = "ecs:service:DesiredCount"
  role_arn = "arn:aws:iam::428324370204:role/ecsAutoscaleRole"
  min_capacity = 1
  max_capacity = 2
}

resource "aws_appautoscaling_policy" "policy" {
  name = "${aws_appautoscaling_target.target.name}"
  resource_id = "service/${aws_ecs_cluster.cluster.name}/${aws_ecs_service.service.name}"
  adjustment_type = "ChangeInCapacity"
  cooldown = 300
  metric_aggregation_type = "Average"
  step_adjustment {
    metric_interval_lower_bound = 0
    scaling_adjustment = 1
  }
}

Expected Behavior

The aws_appautoscaling_target would be updated and the aws_appautoscaling_policy would still be attached.

Actual Behavior

The aws_appautoscaling_target was deleted and re-created, but the aws_appautoscaling_policy was lost in the process. A subsequent terraform apply will add it back, but it either should not have been removed or it should also have been recreated along with the aws_appautoscaling_target.

Steps to Reproduce

Please list the steps required to reproduce the issue, for example:

1. terraform apply
2. change aws_appautoscaling_target.target.max_capacity to 3
3. terraform apply (causes the policy detachment)
4. terraform apply (reattaches the policy)

Important Factoids

According to the AWS docs, the aws_appautoscaling_target can be created as well as updated via RegisterScalableTarget. Perhaps this could be used instead of recreating the aws_appautoscaling_target on update.

[fabienrenaud]

Still an issue with terraform 0.9.8.
A lot of people are having this issue.

[ckyoog]

I have same problem. I originally posted my case in issue terraform#8099.

I post it here again, hope it can help you guys to reproduce the problem.

resource "aws_appautoscaling_target" "ecs_target" {
  max_capacity       = "${var.max_capacity}"
  min_capacity       = "${var.min_capacity}"
  role_arn           = "${var.global_vars["ecs_as_arn"]}"

  resource_id        = "service/${var.global_vars["ecs_cluster_name"]}/${var.ecs_service_name}"
  scalable_dimension = "ecs:service:DesiredCount"
  service_namespace  = "ecs"
}

resource "aws_appautoscaling_policy" "ecs_cpu_scale_in" {
  adjustment_type         = "${var.adjustment_type}"
  cooldown                = "${var.cooldown}"
  metric_aggregation_type = "${var.metric_aggregation_type}"

  name                    = "${var.global_vars["ecs_cluster_name"]}-${var.ecs_service_name}-cpu-scale-in"
  resource_id             = "service/${var.global_vars["ecs_cluster_name"]}/${var.ecs_service_name}"
  scalable_dimension      = "ecs:service:DesiredCount"
  service_namespace       = "ecs"

  step_adjustment {
    metric_interval_upper_bound = "${var.scale_in_cpu_upper_bound}"
    scaling_adjustment          = "${var.scale_in_adjustment}"
  }

  depends_on = ["aws_appautoscaling_target.ecs_target"]
}

resource aws_appautoscaling_policy.ecs_cpu_scale_in (let it be autoscaling policy) depends on resource aws_appautoscaling_target.ecs_target(let it be autoscaling target).

When I change the value of max_capacity, and then run terraform plan, it shows the autoscaling target is forced to new (it is going to be destroyed and re-added). But nothing will happen to autoscaling policy, which is supposed to be destroyed and re-added as well.

Why is it supposed to? Because in my practice, after terraform apply successfully (which destroys and re-adds the autoscaling target successfully), the autoscaling policy is gone automatically (if you login to aws console, you can see it's gone), so I have to run terraform apply again, the second time, and this time, it will add the autoscaling policy back.

[alexcallihan]

Glad I found this. Noticed it today when dropping the min_capacity on our target. Checked the console later and noticed the policies were gone. Ran another terraform apply and saw they re-created.

[christianclarke]

We are also observing the same problem.

[alexcallihan]

A small workaround for this that appears to be working correctly for my situation is just leveraging the target-id in the name arg for the policy:

name = "${aws_appautoscaling_target.xxxxx.id}-scale-down"

This seems to force a destroy and rebuild.

[christianclarke]

@alexcallihan Awesome. Thank you very much. Can confirm that work-around works as well.

[WolverineFan]

I believe #968 is a duplicate of this issue.

[mmmorris1975]

Verified that @alexcallihan workaround makes apply work as expected when autoscaling target properties are adjusted

[bflad]

We just merged a change to the aws_appautoscaling_target resource in master (releasing in v1.8.0 of the provider) that now supports updating the min/max attributes instead of recreating the target. This should help a lot with this situation!

[bflad]

This has been released in terraform-provider-aws version 1.8.0. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

[christianclarke]

Using v1.8.0 of the AWS provider plugin. We noticed that our ECS service would consistently have the AWS service linked IAM role AWSServiceRoleForApplicationAutoScaling_ECSService regardless of the custom role we gave it in the aws_appautoscaling_target resource. Thereby it wasn't idempotent - Terraform would always try to change the IAM role in aws_appautoscaling_target.

I could have used an "lifecycle_ignore" hook, so Terraform wouldn't manage the IAM role in the aws_appautoscaling_target . But rather than ignore it, this is what I came up with to fix the idempotency. Is there any gotchas anyone can think of ?

data "aws_iam_role" "ecs_service_autoscaling" {
name = "AWSServiceRoleForApplicationAutoScaling_ECSService"
}

resource "aws_appautoscaling_target" "service" {
max_capacity = "${var.max_instances}"
min_capacity = "${var.min_instances}"
resource_id = "service/myecscluster/${aws_ecs_service.service.name}"
role_arn = "${data.aws_iam_role.ecs_service_autoscaling.arn}"
scalable_dimension = "ecs:service:DesiredCount"
service_namespace = "ecs"
}

[dendrochronology]

I'm seeing the same thing; every apply tries to update the role_arn. Have you opened another issue, @christianclarke, or should this be re-opened, @bflad?

I can confirm your workaround solved it, but I'm not yet sure if it's side effect free 😄

[christianclarke]

@dendrochronology

This I think has already been raised. The role in question is a service linked role which AWS insist that your autoscaking service adopts

https://github.com/terraform-providers/terraform-provider-aws/issues/921

[ophintor]

Hi,

This is still not working with Terraform 0.12 and unfortunately the above workaround from @alexcallihan doesn't seem to work anymore :(

In a nutshell, I have an ECS service with an autoscaling target and a couple of policies. Let's say I make a change that forces the recreation of the service/target: the autoscaling policy is still in the state file but it doesnt get recreated after recreating the ECS service and target. When I look in AWS, the servioce is there but the autoscaling policies and the target are just gone.

When I run terraform a second time, then they get recreated:

...
  # module.user-mgmt.aws_appautoscaling_policy.ecs_policy_down_cpu will be created
  + resource "aws_appautoscaling_policy" "ecs_policy_down_cpu" {
      + arn                = (known after apply)
      + id                 = (known after apply)
      + name               = "cpu-scale-down"
      + policy_type        = "StepScaling"
      + resource_id        = "service/Service_Finder_dptest/service-finder_dptest_user-mgmt"
      + scalable_dimension = "ecs:service:DesiredCount"
      + service_namespace  = "ecs"

      + step_scaling_policy_configuration {
          + adjustment_type         = "ChangeInCapacity"
          + cooldown                = 300
          + metric_aggregation_type = "Average"

          + step_adjustment {
              + metric_interval_upper_bound = "0"
              + scaling_adjustment          = -1
            }
        }
    }

  # module.user-mgmt.aws_appautoscaling_policy.ecs_policy_up_cpu will be created
  + resource "aws_appautoscaling_policy" "ecs_policy_up_cpu" {
      + arn                = (known after apply)
      + id                 = (known after apply)
      + name               = "cpu-scale-up"
      + policy_type        = "StepScaling"
      + resource_id        = "service/Service_Finder_dptest/service-finder_dptest_user-mgmt"
      + scalable_dimension = "ecs:service:DesiredCount"
      + service_namespace  = "ecs"

      + step_scaling_policy_configuration {
          + adjustment_type         = "ChangeInCapacity"
          + cooldown                = 60
          + metric_aggregation_type = "Average"

          + step_adjustment {
              + metric_interval_lower_bound = "0"
              + scaling_adjustment          = 1
            }
        }
    }

  # module.user-mgmt.aws_appautoscaling_target.ecs_target will be created
  + resource "aws_appautoscaling_target" "ecs_target" {
      + id                 = (known after apply)
      + max_capacity       = 20
      + min_capacity       = 2
      + resource_id        = "service/Service_Finder_dptest/service-finder_dptest_user-mgmt"
      + role_arn           = (known after apply)
      + scalable_dimension = "ecs:service:DesiredCount"
      + service_namespace  = "ecs"
    }
...

Any chance this could be looked into? Thanks!

My version:

$ terraform version
Terraform v0.12.4
+ provider.archive v1.2.2
+ provider.aws v2.19.0
+ provider.random v2.1.2
+ provider.template v2.1.2
+ provider.tls v2.0.1

[bflad]

Hi folks 👋 If you would like to report potentially lingering issues, please file a new bug report following the issue template.

[hashibot[bot]]

I'm going to lock this issue because it has been closed for _30 days_ ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!