Handling DNS for Private Azure Kubernetes Service Clusters

Question

Pulumi · Accepted Answer

When setting up a private Azure Kubernetes Service (AKS) cluster, you typically want to ensure that it can be accessed and managed securely. One part of this setup is to configure the DNS so that the Kubernetes API server and other services within the cluster can be resolved within the cluster's virtual network.

The Pulumi resources you'll use for this setup are:

1. `AzureNative.Network.PrivateDnsZone`: Represents a DNS zone within the Azure Private DNS that can be used to manage and resolve domain names in a virtual network without needing a public IP address.
   
2. `AzureNative.Network.PrivateEndpoint`: Creates a Private Endpoint which securely connects services within Azure without exposing the service to the public internet.

3. `AzureNative.Network.PrivateEndpointDnsZoneGroup`: Associates the Private Dns Zone with the Private Endpoint, so DNS queries for the zone are correctly resolved within the virtual network.

Here's a Pulumi Python program that sets up DNS for a private Azure Kubernetes Service cluster:

```python
import pulumi
import pulumi_azure_native as azure_native

# Replace these variables with your specific information
resource_group_name = "my-resource-group"
private_dns_zone_name = "private.akstest.local"
private_endpoint_name = "aks-private-endpoint"
# Assume the network and subnet are already created and their IDs are known
virtual_network_id = "/subscriptions/subid/resourceGroups/rg1/providers/Microsoft.Network/virtualNetworks/vnet1"
subnet_id = "/subscriptions/subid/resourceGroups/rg1/providers/Microsoft.Network/virtualNetworks/vnet1/subnets/subnet1"

# Create an Azure Resource Group if not already existing
resource_group = azure_native.resources.ResourceGroup("resource-group",
    resource_group_name=resource_group_name)

# Create the private DNS zone
private_dns_zone = azure_native.network.PrivateZone("private-dns-zone",
    resource_group_name=resource_group.name,
    private_zone_name=private_dns_zone_name)

# Create a private endpoint for the AKS cluster
private_endpoint = azure_native.network.PrivateEndpoint("private-endpoint",
    resource_group_name=resource_group.name,
    private_endpoint_name=private_endpoint_name,
    location=resource_group.location,
    subnet=azure_native.network.SubnetArgs(id=subnet_id))

# Associate the private DNS zone with the private endpoint
private_dns_zone_group = azure_native.network.PrivateDnsZoneGroup("private-dns-zone-group",
    private_dns_zone_configs=[azure_native.network.PrivateDnsZoneConfigArgs(
        private_dns_zone_id=private_dns_zone.id,
        name="aks-private-dns-zone-config"
    )],
    private_endpoint_name=private_endpoint.name,
    resource_group_name=resource_group.name
)

# Export the DNS zone name to be used in DNS queries
pulumi.export('private_dns_zone_name', private_dns_zone.name)
# Export the Private Endpoint ID for reference
pulumi.export('private_endpoint_id', private_endpoint.id)
```

Here's what each part of this program does:

- We define some variables for the resource group, DNS zone, and endpoint names along with the network details. These are placeholders and should be replaced with actual values from your Azure setup.
  
- The `ResourceGroup` resource is where all other resources in this example will be placed. This gives us a way to manage the lifecycle of all related resources together.

- We then create the `PrivateZone` within the specified resource group. Private zones in Azure DNS are used to manage the DNS records for a domain within a private network only.

- The `PrivateEndpoint` resource is created in the specified subnet and is what creates the secure connection to services in Azure without exposing them to the public internet.

- Finally, `PrivateDnsZoneGroup` is what glues the private endpoint and private zone together; it ensures that DNS queries for the domain are resolved within the virtual network via the private endpoint.

- The `pulumi.export` commands make the names of the created DNS zone and the private endpoint ID available as outputs once Pulumi applies the code. These outputs can be used to reference these resources in subsequent configurations or for validation.

This program does not cover the creation of AKS or network resources but focuses on how you would handle the DNS for an AKS cluster that's already set up to be private. If you need to create those resources, you would include additional Pulumi resources and code that define them.