Add huaweicloud_compute_volume_attach ordering capacity

[marciobarbato]

Current Terraform Version

1.5.1

Use-cases

When creating Terraform Modules for ECS instances, every now and then I have to use huaweicloud_compute_volume_attach to attach data disks to the VMs and usually I want this to be attached on a certain order e.g. Disk1 128Gb and Disk2 512 Gb, currently it's impossible to determine which order the disks will get attached to the VM.

Attempted Solutions

This is the code I'm currently using on my terraform module

variable "dataDiskSize" {
  default     = [{ size = 128, type = "SAS" },{ size = 512, type = "SAS" }]
}

....


resource "huaweicloud_compute_volume_attach" "diskattachment" {
  count       = length(var.dataDiskSize)
  instance_id = huaweicloud_compute_instance.genericLinux.id
  volume_id   = element(huaweicloud_evs_volume.dataDisk[*].id, count.index)
}

Proposal

Please add a property to allow order control while attaching the disk to the vm

References

[niuzhenguo]

Thanks for raising this, but we can't control the order if you use count because it will do volume attachment parallelly which controlled by terrafrom core.

There are 2 ways to achieve this:

1. You can set -parallelism=1 with terraform apply to make it do one by one, for more information about this you can run terraform apply --help and find -parallelism=n.
2. Do not use count and add depends_on for the two volume_attachment resources to force their order.

[marciobarbato]

Yea, I think that depends on would be great, however this was an example scenario, since this is a module I'd like to have it prepared for multiple disks, it can be two but also can be 10, 12 etc

[niuzhenguo]

Unforturnately, depends_on will not work for this multiple disks senario :(
The only way is to use multiple modules for 2, 10, 12 disks...

[marciobarbato]

any chance of changing terraform provider behavior to inform the "device" we would like to use within the OS ? like a property to attach it to slot 1,2..10 ?

[niuzhenguo]

Actually, we have a device parameter on API side, but it's not ensure and has many limitations. Maybe you can ask for ECS guys to see more information about that.

[niuzhenguo]

You can refer to this parameter,
https://registry.terraform.io/providers/huaweicloud/huaweicloud/latest/docs/resources/compute_volume_attach#device