Module consul-cluster : aws_autoscaling_attachment broken

[LeComptoirDesPharmacies]

Hi,

Since terraform AWS provider 2.21.0, it seems that we can no more use safely aws_autoscaling_attachment as described in your consul-cluster README. (See issue : hashicorp/terraform-provider-aws#9513)

Indeed, if we use aws_autoscaling_attachment to attach target groups to ASG created by consul-cluster, next apply on consul cluster remove the target groups of load balancer.

Documentation (https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/autoscaling_attachment) recommends that you put ignore_changes on aws_autoscaling_group ressources :

to prevent unintended resource updates, the aws_autoscaling_group resource must be configured to ignore changes to the load_balancers and target_group_arns arguments within a lifecycle configuration block.

Do you agree with this ? Do you have any workaround ?

Thanks in advance for your answer.
Yours faithfully,
LCDP

[brikis98]

Are you seeing an issue if you use both target_groups param on aws_autoscaling_group and the aws_autoscaling_attachment resource? Or you get an issue if you use just one of them? Could you share the code and issue you're seeing?

[LeComptoirDesPharmacies]

Hi @brikis98,

In fact consul_cluster do not use target_groups field so it is always omitted in module. (

terraform-aws-consul/modules/consul-cluster/main.tf

Line 14 in ddaed27

resource "aws_autoscaling_group" "autoscaling_group" {

)

I just use the aws_autoscaling_attachment as the documentation describe. (https://github.com/hashicorp/terraform-aws-consul/blob/master/modules/consul-cluster/README.md#how-do-you-connect-load-balancers-to-the-auto-scaling-group-asg)

Here is a "simple" reproducer :
https://gist.github.com/LeComptoirDesPharmacies/3022db2067c3a98ba7d64fab1d17ab5b

If you apply once : ASG > Load Balancing menu will show the LB target groups.
If you apply twice : ASG > Load balancing menu show nothing
If you apply thrice : ASG > Load Balancing menu will show the LB target groups.
etc...

Then, you can check the fix by replacing the module source to : github.com/LeComptoirDesPharmacies/terraform-aws-consul//modules/consul-cluster?ref=bugfix%2Fconsul-cluster-asg-attachment

Yours faithfully,
LCDP

[brikis98]

Understood, thanks!