Kubenet networking for Azure environments in Cloudera Data Warehouse service

Kubenet networking is a software-defined layer of network abstraction that is used to run multiple separate, discrete virtualized network layers over the Azure virtual network. You use kubenet networking to increase the number of IP addresses available to support nodes in your CDW cluster on Azure.

Default CDW networking

By default, CDW uses Azure Container Networking Interface (CNI). With Azure CNI, every pod gets an IP address from the node subnet and is accessed directly. Each IP address must be unique across your network space, and you must plan for them in advance of deploying your CDW cluster. Each node has a configuration parameter for the maximum number of pods that it can support. The equivalent number of IP addresses per executor node is reserved up front for it. This requires advanced planning and it can often lead to IP address exhaustion. As an alternative, you must rebuild the cluster in large subnets so your cluster can meet your applications' demands. You can configure the maximum pods that are deployable to an executor node when you create the cluster or when you create new executor node pools. However, if you do not specify the maximum number of pods for the maxPods property when you create new executor node pools, by default each executor node gets 30 pods (with one IP address per pod).

About using the kubenet networking feature

To avoid IP address exhaustion, you can enable the kubenet networking feature when you activate an Azure environment to use with CDW. For a full description of kubenet networking in AKS, see the Microsoft documentation.

How kubenet compares to Azure CNI

The following calculations compare kubenet to Azure CNI:

  • kubenet: A simple /24 IP address range can support up to 251 executor nodes in the cluster. Keep in mind that Azure virtual network subnet reserves the first three IP addresses for management operations. 251 executor nodes can support up to 27,610 pods when you use a default maximum of 110 pods per executor node.
  • Azure CNI: The same basic /24 IP address subnet range can only support a maximum of 8 executor nodes in the cluster. 8 executor nodes can only support up to 240 pods with a default maximum of 30 pods per executor node.

Guidelines for choosing kubenet networking in CDW

The following guidelines help you to decide whether to enable kubenet networking when you are activating Azure environments for CDW:

  • Use kubenet networking when the following conditions are true for your CDW deployment:
    • You have a limited IP address space.
    • Most of the pod communication is within the cluster.
    • You do not need advanced AKS features such as virtual executor nodes or to secure traffic between pods with network policies. See Microsoft documentation for more information on Azure network policies.
  • Do not use the kubenet networking (use Azure CNI) when the following is true for your CDW deployment:
    • You have adequate IP addresses available.
    • Most of the pod communication is to resources outside of the cluster.
    • You do not want to manage User Defined Routing (UDR) for connectivity between pods across executor nodes, which is required for kubenet.
    • You do not need advanced AKS features as described above.

Limitations of kubenet networking in CDW on Azure environments

If you choose kubenet networking when you activate Azure environments for CDW, the following limitations exist:

  • Permissions must be assigned before cluster creation. Ensure that you are using a service principal with write permissions on your customer subnet and custom route table.
  • Managed identities are not supported with custom route tables in kubenet.
  • A custom route table must be associated to the subnet before you create the AKS cluster. Afterwards, this route table cannot be updated. All routing rules must be added or removed from the initial route table before you create the AKS cluster.
  • All subnets within an AKS virtual network must use the same route table.
  • Every AKS cluster must use a unique route table. You cannot re-use a route table with multiple clusters.

Node count limits

The following executor node count limits apply to whether you use kubenet networking or not:

  • With kubenet networking, you can have up to 400 executor nodes/AKS cluster.
  • Without kubenet networking, which uses Azure CNI, you can have up to 1,000 executor nodes/AKS cluster.