Load balancer creation/management sample code?

Library name and version

Azure.ResourceManager.Network 1.0.0-beta.7

Query/Question

I’ve been struggling with creating a load balancer using the Azure.ResourceManager.Network 1.0.0-beta.7 SDK and haven’t found any SDK specific sample code or examples.

Question 1: Is there any sample code for managing load balancers with the .NET Azure ARM SDK?

I’ve done a lot of Googling and haven’t found anything but samples for the Azure CLI, PowerShell, and older SDKs. I did find a couple samples here but these didn’t cover load balancers.

Question 2: What’s the process for adding a NIC to a backend address pool?

I’ve tried the pseudo code below but I’m unable to initialize a LoadBalancerBackendAddress because setting the NetworkInterfaceIPConfigurationId property throws a NullReferenceException. This happens because the default LoadBalancerBackendAddress() constructor doesn’t initialize the internal NetworkInterfaceIPConfiguration property.

var azure                   = new ArmClient(new DefaultAzureCredential());
var location                = new AzureLocation("centralus");
var resourceGroupCollection = azure.GetResourceGroupCollection();
var resourceGroup           = (await resourceGroupCollection.GetAsync("my-resources")).Value;
var loadBalancerCollection  = resourceGroup.GetLoadBalancers();
var publicAddress           = /* set to an existing public IP address resource */
var nic                     = /* set to the primary (and only) NIC resource for a deployed VM */

// Create a load balancer with a single frontend and and an empty backend.

var loadBalancerData = 
    new LoadBalancerData()
    {
        Location = location,
        Sku      = new LoadBalancerSku() { Name = "Standard", Tier = "Regional" }
    };

loadBalancerData.FrontendIPConfigurations.Add(
    new FrontendIPConfigurationData()
    {
        Name            = "my-frontend",
        PublicIPAddress = publicAddress.Data,
    });

loadBalancerData.BackendAddressPools.Clear();
loadBalancerData.BackendAddressPools.Add(
    new BackendAddressPoolData()
    {
         Name = "my-backend"
    });

loadBalancer = (await loadBalancerCollection.CreateOrUpdateAsync(WaitUntil.Completed, "my-loadbalancer", WithNetworkTags(loadBalancerData))).Value;

// Add a NIC to the backend and update the load balancer.

var nicIpConfigId = nic.GetNetworkInterfaceIPConfigurations().First().Id;

loadBalancer.Data.BackendAddressPools.First().Add(
    new LoadBalancerBackendAddress()
    {
        Name                              = "my-address",
        NetworkInterfaceIPConfigurationId = nicIpConfigId  // <--- Throws a NullReferenceException because the R/O backing property is NULL
    });
    
loadBalancer = (await loadBalancerCollection.CreateOrUpdate(WaitUntil.Completed, loadBalancer.Name, loadBalancer.Data)).Value;

For fun, I tried using reflection to initialize the internal NetworkInterfaceIPConfiguration property’s backing property to a new WritableSubResource. This fixed the nullref exception, but the load balancer’s backend address pool was still empty after the update.

Environment

.NET SDK (reflecting any global.json): Version: 6.0.300 Commit: 8473146e7d

Runtime Environment: OS Name: Windows OS Version: 10.0.19044 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\6.0.300\

Host (useful for support): Version: 6.0.5 Commit: 70ae3df4a6

.NET SDKs installed: 3.1.419 [C:\Program Files\dotnet\sdk] 5.0.407 [C:\Program Files\dotnet\sdk] 5.0.408 [C:\Program Files\dotnet\sdk] 6.0.101 [C:\Program Files\dotnet\sdk] 6.0.105 [C:\Program Files\dotnet\sdk] 6.0.300 [C:\Program Files\dotnet\sdk]

.NET runtimes installed: Microsoft.AspNetCore.App 3.1.24 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.25 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.16 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 6.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 6.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.NETCore.App 3.1.24 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.25 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.16 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 6.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 6.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.WindowsDesktop.App 3.1.24 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 3.1.25 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 5.0.16 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 6.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 6.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

[jefflill]

I figured this out: you need to add a NIC to a backend address pool from the NIC side, something like:

var resourceGroup           = (await resourceGroupCollection.GetAsync("my-resources")).Value;
var loadBalancerCollection  = resourceGroup.GetLoadBalancers();
var nicCollection           = resourceGroup.GetNetworkInterfaces();
var nic                     = (await nicCollection.GetAsync("my-nic")).Value;

// Create a load balancer with a single frontend and and an empty backend.

var loadBalancerData =
    new LoadBalancerData()
    {
        Location = location,
        Sku = new LoadBalancerSku() { Name = "Standard", Tier = "Regional" }
    };

loadBalancerData.FrontendIPConfigurations.Add(
    new FrontendIPConfigurationData()
    {
        Name            = "my-frontend",
        PublicIPAddress = publicAddress.Data,
    });

loadBalancerData.BackendAddressPools.Clear();
loadBalancerData.BackendAddressPools.Add(
    new BackendAddressPoolData()
    {
        Name = "my-backend"
    });

loadBalancer = (await loadBalancerCollection.CreateOrUpdateAsync(WaitUntil.Completed, "my-loadbalancer", WithNetworkTags(loadBalancerData))).Value;

// Add an existing NIC to the load balancer's backend address pool.

var ipConfiguration = nic.Data.IPConfigurations.First();

ipConfiguration.LoadBalancerBackendAddressPools.Add(
    new BackendAddressPoolData()
    {
        Id = loadBalancerData.BackendAddressPools.Single(pool => pool.Name == "my-backend").Data.Id
    });

nic = (await nicCollection.CreateOrUpdateAsync(WaitUntil.Completed, "my-nic", azureVm.Nic.Data)).Value;

What threw me here, was that the BackendAddressPoolData.LoadBalancerBackendAddresses property is a read/write IList instead of a IReadOnlyList. This led me to believe that I could manage the NIC references here. I suppose this is R/W so that developers can add static IP addresses rather then adding NICs.

So, I guess this issue has turned into a request for load balancer sample code.

[ArthurMa1978]

@jefflill thank you for reaching us, and provide this useful code, we will have a sampe for this scenario. @fengzhou-msft will follow up.