Maximizing Resilience in Azure: A Guide to Three-Tier Architecture with AKS and MongoDB

Introduction

In this guide, we’ll explore the process of designing and deploying a highly available, resilient three-tier application architecture on Azure. This architecture will use Azure Kubernetes Service (AKS), Azure Application Gateway, and MongoDB, with the entire structure distributed across three Availability Zones for maximum resilience and high availability.

Architecture Overview Broadly, our architecture involves:

  • Web Tier: Azure Application Gateway
  • Business Tier: Azure Kubernetes Service (AKS) running NGINX (serving as a reverse proxy service), a Node.js API service, and Python batch processors
  • Data Tier: MongoDB Replica Set

Each tier will be hosted in dedicated subnets, each situated in a different Availability Zone, thus bolstering resiliency and high availability.

Designing the Baseline Network

Establishing the Foundation Network with Zonal Redundant Architecture and Azure VNets The initial step involves designing and setting up the baseline network using Azure Virtual Networks (VNets) as the backbone of our Zonal redundant architecture. We’ll create three public subnets for the Azure Application Gateway (Web Tier), three private subnets for AKS (Business Tier), and three private subnets for our MongoDB instances (Data Tier). Each subnet will be provisioned in a separate Availability Zone, thereby creating a highly resilient and available network structure.

When setting up the VNet, ensure sufficient address space for the required subnets. Select an address range within the standard private IP address blocks, namely 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16.

Configuring Azure Application Gateway

Now we Azure Application Gateway and Managing SSL Certificates With our network foundation in place, we can start configuring the Azure Application Gateway. This gateway will act as our internet-facing load balancer, directing incoming internet traffic to the AKS clusters in the business tier.

When creating a routing policy for the Application Gateway, you’ll set rules governing how traffic should be routed. For instance, URL path-based routing can be used to guide traffic based on the incoming URL path pattern.

Part of configuring your Azure Application Gateway involves installing and managing SSL certificates to enable secure connections. You can upload your SSL certificate and its private key through the Azure portal or Azure Resource Manager templates. Remember to keep your certificates updated, or automate certificate renewal to ensure your services stay secure and accessible.

Setting Up AKS and Deploying Services

Setting Up AKS, Deploying Services, and Configuring AGIC With our network and web tier prepared, we can now establish the AKS cluster and deploy our services.

Azure Kubernetes Service (AKS) will host our NGINX reverse proxy service, Node.js API service, and Python batch processors. These services will be deployed within the three private subnets created in the business tier.

To expose our services, we’ll use the Azure Application Gateway Ingress Controller (AGIC). AGIC monitors the AKS cluster and updates the Application Gateway as it detects changes.

To forward traffic to the NGINX and API services via Azure Application Gateway using AGIC, you’ll need to create Kubernetes Ingress resources. These resources define how incoming traffic should be routed to the services within your cluster. When AGIC sees these Ingress resources, it updates the Azure Application Gateway configuration to reflect these routes.

Moreover, configurations and secrets for MongoDB or other services can be managed within the cluster using Kubernetes ConfigMaps and Secrets, or other secure tools such as HashiCorp Vault. These tools help maintain the security and integrity of your application by securely storing and managing sensitive data.

Deploying MongoDB Replica Set

Deploying MongoDB Replica Set Finally, we’ll set up our data tier by deploying a three-member MongoDB replica set across the three private subnets allocated to our databases.

MongoDB replica sets provide redundancy and high availability, forming the bedrock of all production deployments. This setup includes two or more nodes that hold the same data set. Replication amplifies redundancy and boosts data availability with multiple copies of data on different database servers.

Conclusion

By following these steps, you can create a resilient, highly available three-tier architecture on Azure using AKS, Azure Application Gateway, and MongoDB. Each component is spread across three Availability Zones, ensuring maximum resilience and high availability for your application requirements.

Always prioritize security throughout this process. Azure offers numerous tools for managing network security, such as Network Security Groups (NSGs) and Azure Key Vault for managing encryption keys. Also, consider using a jumpbox for secure administrative tasks.

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