Having an issue with Azure scaling set with terraform - terraform

Question

Not sure what I'm doing wrong. I only have one NAT rule in the terraform config and I'm not using a NAT pool.
Error:
azurerm_virtual_machine_scale_set.development-eastus-ss: compute.VirtualMachineScaleSetsClient#CreateOrUpdate: Failure sending request: StatusCode=400 -- Original Error: Code="InvalidRequestFormat" Message="Cannot parse the request." Details=[{"code":"InvalidJsonReferenceWrongType","message":"Reference Id /subscriptions/sub-id/resourceGroups/prod-eastus-rg/providers/Microsoft.Network/loadBalancers/development-eastus-lb/inboundNatRules/development-eastus-lb-nat-http is referencing resource of a wrong type. The Id is expected to reference resources of type loadBalancers/inboundNatPools. Path Properties.UpdateGroups[0].NetworkProfile.networkInterfaceConfigurations[0].properties.ipConfigurations[0].properties.loadBalancerInboundNatPools[0]."}]
NAT Rule:
resource "azurerm_lb_nat_rule" "development-eastus-lb-nat-http" {
name = "development-eastus-lb-nat-http"
resource_group_name = "${var.resource_group_name}"
loadbalancer_id = "${azurerm_lb.development-eastus-lb.id}"
protocol = "Tcp"
frontend_port = 80
backend_port = 8080
frontend_ip_configuration_name = "development-eastus-lb-frontend"

Answer 1

Looks like this is an issue with trying to bind a single nat rule to a scaleset. As the error suggests, it is expecting a nat pool rather than a nat rule a nat pool will allow the load balancer and the scale set to build a group of rules where the load balancer will expose a different port per underlying VM to the same port on the VM.
Think about RDP where you want to be able to remote onto a specific VM, this would enable this by giving you a unique port to use that maps onto that VM.
resource "azurerm_lb_nat_pool" "test" {
resource_group_name = "${azurerm_resource_group.test.name}"
loadbalancer_id = "${azurerm_lb.test.id}"
name = "SampleApplicationPool"
protocol = "Tcp"
frontend_port_start = 80
frontend_port_end = 81
backend_port = 8080
frontend_ip_configuration_name = "PublicIPAddress"
}
If however you are looking to run a service such as a HTTP website on a different port internally than externally, such as 8080 on the local network and then port 80 on the external public network, then I would take a look at the lb rule as this specifically allows you to set the ports, as shown below.
resource "azurerm_lb_rule" "test" {
resource_group_name = "${azurerm_resource_group.test.name}"
loadbalancer_id = "${azurerm_lb.test.id}"
name = "LBRule"
protocol = "Tcp"
frontend_port = 3389
backend_port = 3389
frontend_ip_configuration_name = "PublicIPAddress"
}
Hopefully this helps