How to check if name already exists? Azure Ressource Manager Template - json

Question

is it possible to check, in an ARM Template, if the name for my Virtual Machine already exists?
I am developing a Solution Template for the Azure Marketplace. Maybe it is possible to set a paramter in the UiDefinition uniqe?
The goal is to reproduce this green Hook

Answer 1

A couple notes...
VM Names only need to be unique within a resourceGroup, not within the subscription
Solution Templates must be deployed to empty resourceGroups, so collisions with existing resources aren't possible
For solution templates the preference is that you simply name the VMs for the user, rather than asking - use something that is appropriate for the workload (e.g. jumpbox) - not all solutions do this but we're trying to improve that experience
Given that it's not likely we'll ever build a control that checks for naming collisions on resources without globally unique constraints.
That help?

Answer 2

This looks impossible, according to the documentation.
There are no validation scenarious.

Answer 3

I assume that you should be using the Microsoft.Common.TextBox UI element in your createUiDefinition.json.
I have tried to reproduce a green check by creating a simple createUiDefinition.json as below with a Microsoft.Common.TextBox UI element as shown below.
{
"$schema": "https://schema.management.azure.com/schemas/0.1.2-preview/CreateUIDefinition.MultiVm.json",
"handler": "Microsoft.Compute.MultiVm",
"version": "0.1.2-preview",
"parameters": {
"basics": [
{
"name": "textBoxA",
"type": "Microsoft.Common.TextBox",
"label": "VM Name",
"defaultValue": "",
"toolTip": "Please enter a VM name",
"constraints": {
"required": true
},
"visible": true
}
],
"steps": [],
"outputs": {}
}
}
I am able to reproduce the green check beside the VM Name textbox as shown below:
However, this green check DOES NOT imply the VM Name is Available.
This is because based on my testing, even if I use an existing VM Name in the same subscription, it is still showing the green check.
Based on the official documented constraints that are supported by the Microsoft.Common.TextBox UI element, it DOES NOT VALIDATE Name Availability.
Hope this helps!

Answer 4

While bmoore's point is correct that it's unlikely you would ever need this for a VM (nor is there an API for it), there are other compute resources that do have global naming requirements.
As of 2022 this concept is possible now with the use of the ArmApiControl UI element. It allows you to call ARM apis as part of validation in the createUiDefinition.json. Here is an example using the check name API for an Azure App service.
{
"$schema": "https://schema.management.azure.com/schemas/0.1.2-preview/CreateUIDefinition.MultiVm.json#",
"handler": "Microsoft.Azure.CreateUIDef",
"version": "0.1.2-preview",
"parameters": {
"basics": [
{}
],
"steps": [
{
"name": "domain",
"label": "Domain Names",
"elements": [
{
"name": "domainInfo",
"type": "Microsoft.Common.InfoBox",
"visible": true,
"options": {
"icon": "Info",
"text": "Pick the domain name that you want to use for your app."
}
},
{
"name": "appServiceAvailabilityApi",
"type": "Microsoft.Solutions.ArmApiControl",
"request": {
"method": "POST",
"path": "[concat(subscription().id, '/providers/Microsoft.Web/checknameavailability?api-version=2021-02-01')]",
"body": "[parse(concat('{\"name\":\"', concat('', steps('domain').domainName), '\", \"type\": \"Microsoft.Web/sites\"}'))]"
}
},
{
"name": "domainName",
"type": "Microsoft.Common.TextBox",
"label": "Domain Name Word",
"toolTip": "The name of your app service",
"placeholder": "yourcompanyname",
"constraints": {
"validations": [
{
"regex": "^[a-zA-Z0-9]{4,30}$",
"message": "Alphanumeric, between 4 and 30 characters."
},
{
"isValid": "[not(equals(steps('domain').appServiceAvailabilityApi.nameAvailable, false))]",
"message": "[concat('Error with the url: ', steps('domain').domainName, '. Reason: ', steps('domain').appServiceAvailabilityApi.reason)]"
},
{
"isValid": "[greater(length(steps('domain').domainName), 4)]",
"message": "The unique domain suffix should be longer than 4 characters."
},
{
"isValid": "[less(length(steps('domain').domainName), 30)]",
"message": "The unique domain suffix should be shorter than 30 characters."
}
]
}
},
{
"name": "section1",
"type": "Microsoft.Common.Section",
"label": "URLs to be created:",
"elements": [
{
"name": "domainExamplePortal",
"type": "Microsoft.Common.TextBlock",
"visible": true,
"options": {
"text": "[concat('https://', steps('domain').domainName, '.azurewebsites.net - The main app service URL')]"
}
}
],
"visible": true
}
]
}
],
"outputs": {
"desiredDomainName": "[steps('domain').domainName]"
}
}
}
You can copy the above code and test it in the createUiDefinition.json sandbox azure provides.