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Version: 3.6

Guidelines for creating an AKS cluster for ScalarDB Server

This document explains the requirements and recommendations for creating an Azure Kubernetes Service (AKS) cluster for ScalarDB Server deployment. For details on how to deploy ScalarDB Server on an AKS cluster, see Deploy ScalarDB Server on AKS.

Before you begin

You must create an AKS cluster based on the following requirements, recommendations, and your project's requirements. For specific details about how to create an AKS cluster, refer to the following official Microsoft documentation based on the tool you use in your environment:

Requirements

When deploying ScalarDB Server, you must:

  • Create the AKS cluster by using Kubernetes version 1.21 or higher.
  • Configure the AKS cluster based on the version of Kubernetes and your project's requirements.

Recommendations (optional)

The following are some recommendations for deploying ScalarDB Server. These recommendations are not required, so you can choose whether or not to apply these recommendations based on your needs.

Create at least three worker nodes and three pods

To ensure that the AKS cluster has high availability, you should use at least three worker nodes and deploy at least three pods spread across the worker nodes. You can see the sample configurations of podAntiAffinity for making three pods spread across the worker nodes.

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If you place the worker nodes in different availability zones (AZs), you can withstand an AZ failure.

Use 4vCPU / 8GB memory nodes for the worker node in the ScalarDB Server node pool

From the perspective of commercial licenses, resources for one pod running ScalarDB Server are limited to 2vCPU / 4GB memory. In addition to the ScalarDB Server pod, Kubernetes could deploy some of the following components to each worker node:

  • ScalarDB Server pod (2vCPU / 4GB)
  • Envoy proxy
  • Your application pods (if you choose to run your application's pods on the same worker node)
  • Monitoring components (if you deploy monitoring components such as kube-prometheus-stack)
  • Kubernetes components

With this in mind, you should use a worker node that has at least 4vCPU / 8GB memory resources and use at least three worker nodes for availability, as mentioned in Create at least three worker nodes and three pods.

However, three nodes with at least 4vCPU / 8GB memory resources per node is the minimum for production environment. You should also consider the resources of the AKS cluster (for example, the number of worker nodes, vCPUs per node, memory per node, ScalarDB Server pods, and pods for your application), which depend on your system's workload. In addition, if you plan to scale the pods automatically by using some features like Horizontal Pod Autoscaling (HPA), you should consider the maximum number of pods on the worker node when deciding the worker node resources.

Create a node pool for ScalarDB Server pods

AKS creates one system node pool named agentpool that is preferred for system pods (used to keep AKS running) by default. We recommend creating another node pool with user mode for ScalarDB Server pods and deploying ScalarDB Server pods on this additional node pool.

Configure cluster autoscaler in AKS

If you want to scale ScalarDB Server pods automatically by using Horizontal Pod Autoscaler, you should configure cluster autoscaler in AKS too. For details, refer to the official Microsoft documentation at Cluster autoscaler.

In addition, if you configure cluster autoscaler, you should create a subnet in a virtual network (VNet) for AKS to ensure a sufficient number of IPs exist so that AKS can work without network issues after scaling. The required number of IPs varies depending on the networking plug-in. For more details about the number of IPs required, refer to the following:

Create the AKS cluster on a private network

You should create the AKS cluster on a private network (private subnet in a VNet) since ScalarDB Server does not provide any services to users directly via internet access. We recommend accessing ScalarDB Server via a private network from your applications.

Create the AKS cluster by using Azure CNI, if necessary

The AKS default networking plug-in is kubenet. If your requirement does not match kubenet, you should use Azure Container Networking Interface (CNI).

For example, if you want to deploy multiple ScalarDB Server environments on one AKS cluster (e.g., deploy a multi-tenant ScalarDB Server) and you want to control the connection between each tenant by using Kubernetes NetworkPolicies, kubenet supports only the Calico Network Policy, which the Azure support team does not support. Please note that the Calico Network Policy is supported only by the Calico community or through additional paid support.

The Azure support and engineering teams, however, do support Azure CNI. So, if you want to use Kubernetes NetworkPolicies and receive support from the Azure support team, you should use Azure CNI. For more details about the differences between kubenet and Azure CNI, refer to the following official Microsoft documentation:

Restrict connections by using some security features based on your requirements

You should restrict unused connections in ScalarDB Server. To restrict unused connections, you can use some security features in Azure, like network security groups.

The connections (ports) that ScalarDB Server uses by default are as follows:

  • ScalarDB Server
    • 60051/TCP (accepts requests from a client)
    • 8080/TCP (accepts monitoring requests)
  • Scalar Envoy (used with ScalarDB Server)
    • 60051/TCP (load balancing for ScalarDB Server)
    • 9001/TCP (accepts monitoring requests for Scalar Envoy itself)
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