Getting blank azure public ip output from terraform - azure

Question

In my main terraform file I have:
resource "azurerm_resource_group" "rg" {
name = var.rg_name
location = var.location
}
resource "azurerm_public_ip" "public_ip" {
name = "PublicIP"
location = azurerm_resource_group.rg.location
resource_group_name = azurerm_resource_group.rg.name
domain_name_label = var.domain_name_label
allocation_method = "Dynamic"
}
And in my outputs file I have:
data "azurerm_public_ip" "public_ip" {
name = "PublicIP"
resource_group_name = azurerm_resource_group.rg.name
depends_on = [azurerm_resource_group.rg, azurerm_public_ip.public_ip]
}
output "public_ip" {
value = data.azurerm_public_ip.public_ip.ip_address
}
All the resources including IP get created, however the output is blank. How can I fix this?

Answer 1

Make sure output.tf contains only output tags and main.tf contains resources tags
The following works just fine for me:
Main.tf
resource "azurerm_resource_group" "example" {
name = "resourceGroup1"
location = "West US"
}
resource "azurerm_public_ip" "example" {
name = "acceptanceTestPublicIp1"
resource_group_name = azurerm_resource_group.example.name
location = azurerm_resource_group.example.location
allocation_method = "Static"
tags = {
environment = "Production"
}
}
Output.tf
output "azurerm_public_ip" {
value = azurerm_public_ip.example.ip_address
}
In case you want to have a dependency between resources, use depends_on inside the resource tag.
For example:
depends_on = [azurerm_resource_group.example]
Steps to reproduce:
terraform init
terraform plan
terraform apply
terraform output
Update-
The reason you get blank public IP is since declaring allocation_method = "Dynamic"
From the docs:
Note Dynamic - Public IP Addresses aren't allocated until they're assigned to a
resource (such as a Virtual Machine or a Load Balancer) by design
within Azure.
Full working example with dynamic allocation.

Answer 2

I had the same issue. The actual problem seems to be the dynamic allocation. The IP address is not known until it is actually used by a VM.
In my case, I could solve the issue by adding the VM (azurerm_linux_virtual_machine.testvm) to the depends_on list in the data source:
data "azurerm_public_ip" "public_ip" {
name = "PublicIP"
resource_group_name = azurerm_resource_group.rg.name
depends_on = [ azurerm_public_ip.public_ip, azurerm_linux_virtual_machine.testvm ]
}
Unfortunately, this seems not to be documented in https://www.terraform.io/docs/providers/azurerm/d/public_ip.html