AML Compute Instance fails to build - Invalid Name format

[dram1964]

Describe the bug
When adding an AML Compute Instance User Resource to a workspace, the deployment will fail if:

1. the AML workspace name ends in four numeric characters and
2. the Compute Instance Resource Id ends in four numeric characters

If the above two conditions apply, this results in an 'InvalidResourceName' error, with the following error message: "A name for an Azure ML Compute Instance must be between 3 and 24 characters in length and must use only numbers, letters and minus symbol (-) and must start with letters. Numbers cannot be the ending of the name if the previous character is a minus symbol (-). Please specify a different Azure ML Instance name"

Steps to reproduce

1. Deploy an AML Workspace Service with a resource id ending in four numbers (e.g. 794d166a-d426-4050-be63-e0de1e174098)
2. Deploy an AML Compute Instance with a resource id ending in four numbers (e.g. 440c0bae-c370-4b64-a8e5-0000ab006653)
3. Deployment fails with 'InvalidResourceName' error (ci-40986653)

Source of Error

The error derives from the code in templates/workspace_services/azureml/user_resources/aml_compute/terraform/locals.tf:

  aml_compute_id                 = "${local.short_service_id}${local.short_user_resource_id}"
  aml_compute_instance_name      = "ci-${local.aml_compute_id}"

[marrobi]

Interesting one! Suggest we just get rid of the - chars to avoid this. Any reason this would be a bad idea?

[dram1964]

I like the hyphens. Would be nice to keep them and do something like:

short_vm_size 			= replace(replace(var.vm_size_sku, "Standard_", ""), "_", "")
aml_compute_id                 = "${local.short_service_id}-${local.short_user_resource_id}"
aml_compute_instance_name      = "ci-${local.aml_compute_id}-${local.short_vm_size}"

Not sure if there's a guarantee that the vm_size_sku will begin with "Standard_".

In a perfect world, I'd set the name to: "ci-${user_alias}-${local.aml_compute_id}-${local.short_vm_size}". $user_alias could come from a template parameter

Having the sku in the name, will help when a user double-clicks a notebook and is then asked to choose which compute to run it on.

However if that doesn't work, then dropping the hyphen is a good compromise