Azure Spring Apps integrated with landing zones

This reference architecture deploys the Azure Spring Apps baseline architecture in Azure landing zones.

In this scenario, your organization expects the workload to use federated resources managed by central teams (platform) Centralized management examples include networking for on-premises connectivity, identity access management, and policies. This guidance assumes the organization has adopted Azure landing zones to apply consistent governance and save costs across multiple workloads.

The design choices made in this architecture are covered in the key technical design areas. For more information, see Azure Spring Apps landing zone in the Cloud Adoption Framework.

Architecture

The following diagram depicts the architecture for this approach:

Typical uses for this architecture include:

• Private applications: Internal applications deployed in hybrid cloud environments.
• Public applications: Externally facing applications.

These use cases are similar except for the configuration of security and network traffic rules.

Components

The following sections describe the components of this architecture. The components are divided according to ownership responsibilities to help you identify what to share with the platform teams of the organization. For product documentation about Azure services, see the Related resources section.

Application team-owned resources

Your team is responsible for creating and maintaining the following resources.

• Azure Spring Apps Standard hosts your Java Spring Boot applications in Azure.

• Azure Application Gateway Standard_v2 is the reverse proxy that routes incoming web traffic to Azure Spring Apps. This SKU has integrated Azure Web Application Firewall that inspects traffic for Open Web Application Security Project (OWASP) vulnerabilities.

• Azure Virtual Machines acts as a jump box for management operations.

• Azure Database for MySQL stores application data.

• Azure Key Vault stores secrets and configuration, such as a connection string to the database.

• Log Analytics is a feature of Azure Monitor that's also referred to as Azure Monitor Logs. Log Analytics is the monitoring sink that stores logs and metrics from the application and the Azure services.

• Azure Application Insights is used as an Application Performance Management (APM) tool to collect all application monitoring data and store it directly within Log Analytics.

Platform team-owned resources

This architecture assumes the following resources already exist. The central teams of the organization own and maintain these resources. Your application depends on these services to reduce operational overhead and optimize cost.

• Azure Firewall inspects and restricts egress traffic.

• Azure Bastion provides secure access to the management jump box.

• Azure ExpressRoute provides private connectivity from on-premises to Azure infrastructure.

• Azure DNS provides cross-premises name resolution.

• Azure VPN Gateway connects the application with remote teams in your on-premises network.

Application considerations

The reference implementation includes a sample application that illustrates a typical microservices application hosted in an Azure Spring Apps instance. The following sections provide details about the hosted application. For more information, see PetClinic store sample.

Service discovery

In a microservices pattern, service registry capability must be supported for routing user requests and service-to-service communication.

Services should be able to communicate with other services. When new instances are spawned, they're added to the registry so they can be dynamically discovered. In this architecture, Managed Spring Cloud Service Registry (OSS) is enabled for Azure Spring Apps. This service maintains a registry of live app instances, enables client-side load-balancing, and decouples service providers from clients without relying on a Domain Name Service (DNS).

The Azure Spring Apps instance implements the gateway routing pattern, which provides a single point of entry for external traffic. The gateway routes incoming requests to the active service instances found in the registry. In this design, the pattern is implemented with an open-source implementation of Spring Cloud Gateway. It offers a feature set that includes authentication and authorization, resiliency features, and rate limiting.

Configuration server

For microservices, configuration data must be separated from the code. In this architecture, Azure Spring Apps Config Server enables the management of resources through a pluggable repository that supports local storage and Git repositories.

Redundancy

You can use availability zones when creating an Azure Spring Apps instance.

With this feature, Azure Spring Apps automatically distributes fundamental resources across logical sections of underlying Azure infrastructure. This distribution provides a higher level of availability and protects against hardware failures or planned maintenance events.

Zone redundancy ensures that underlying virtual machine (VM) nodes are distributed evenly across all availability zones. However, zone redundancy doesn't guarantee even distribution of app instances. If an app instance fails because its located zone goes down, Azure Spring Apps creates a new app instance for this app on a node in another availability zone.

If you enable your own resource in Azure Spring Apps, such as your own persistent storage, enable zone redundancy for the resource. For more information, see How to enable your own persistent storage in Azure Spring Apps.

Availability zones aren't supported in all regions. To see which regions support availability zones, see Azure regions with availability zone support.

Scalability

Azure Spring Apps provides autoscaling capabilities out of the box that enable apps to scale based on metric thresholds or during a specific time window. Autoscaling is recommended when apps need to scale up or scale out in response to changing demand.

Azure Spring Apps also supports scaling your applications manually by adjusting CPU, Memory/GB per instance, and App instance counts. This type of scaling is suitable for one-time scaling activity that you might want to perform for certain apps. Adjust the values to meet your application's scaling needs, and ensure your settings are within the maximum limits for each attribute.

Networking considerations

In this design, the workload is dependent on resources owned by the platform team for accessing on-premises resources, controlling egress traffic, and so on. For more information, see Azure Spring Apps landing zone: Network topology and connectivity.

Network topology

The platform team determines the network topology. A hub-spoke topology is assumed in this architecture.

Hub virtual network

The connectivity subscription contains a hub virtual network shared by the entire organization. The network contains networking resources owned and maintained by the platform team. The following platform team resources are in scope for this architecture:

• Azure Firewall controls outbound traffic to the internet.
• Azure Bastion secures access to the management jump box.

Spoke virtual network

The application landing zone has at least one pre-provisioned virtual network that's peered to the hub network. You own the resources in this network, such as the load balancer that routes and protects inbound HTTP/s connections to Azure Spring Apps from the internet.

The pre-provisioned virtual network and peerings must be able to support the expected growth of the workload. Estimate the virtual network size and evaluate the requirements with the platform team regularly. For information, see Virtual network requirements.

VNet injection and subnetting

Azure Spring Apps is deployed into the network via the VNET injection process. This process isolates the application from the internet, systems in private networks, other Azure services, and even the service runtime. Inbound and outbound traffic from the application is allowed or denied based on network rules.

Isolation is achieved through subnets. You're responsible for allocating subnets in the spoke virtual network. Azure Spring Apps requires two dedicated subnets for the service runtime and for Java Spring Boot applications.

The subnets must be dedicated to a single Azure Spring Apps instance. Multiple instances can't share the same subnets.

The minimum size of each subnet is /28. The actual size depends on the number of application instances that Azure Spring Apps can support. For more information, see Using smaller subnet ranges.

Network controls

Azure Application Gateway with Web Application Firewall restricts inbound traffic to the spoke virtual network from the internet. Web Application Firewall rules allow or deny HTTP/s connections.

Traffic within the network is controlled by using network security groups (NSGs) on subnets. NSGs filter traffic according to the configured IP addresses and ports. In this design, NSGs are placed on all the subnets. The Azure Bastion subnet allows HTTPS traffic from the internet, gateway services, load balancers, and the virtual network. Only RDP and SSH communication to the virtual networks is allowed from the subnet.

Private links are used to control connectivity between Azure Spring Apps and other Azure services, such as access to the key vault and database. The private endpoints are placed in a separate subnet.

Application host DNS records should be stored in Azure Private DNS to ensure continued availability during a geographic failure.

Although the connectivity subscription has private DNS zones, create your own Azure Private DNS zones to support the services accessed by private endpoints.

Outbound traffic from the virtual network must be restricted to prevent data exfiltration attacks. This traffic is routed through the centralized Azure Firewall (next hop) that allows or denies the flow by using a fully qualified domain name (FQDN).

Identity and access management

The workload's identity implementation must align with the organizational best practices to ensure the application doesn't violate organizational security or governance boundaries. For more information, see Azure Spring Apps landing zone: Identity and access management.

Microsoft Entra ID is recommended for authenticating users and services that interact with the Azure Spring Apps instance.

The recommended approach is to enable Microsoft Entra managed identities for Azure resources for the application to enable the app to self-authenticate to other services. In this architecture, system-assigned managed identities are used for ease of management.

For authorization, use Azure Role Based Access Control (RBAC) by applying the principle of least privilege when granting permissions.

Monitoring considerations

The Azure landing zone platform provides shared observability resources as part of the management subscriptions. However, provisioning your own monitoring resources is recommended to simplify the overall management of the workload. For more information, see Azure Spring Apps landing zone: Monitor operations.

This architecture creates the following resources:

• Azure Application Insights is the Application Performance Monitoring (APM) solution and is fully integrated into the service through a Java agent. This agent provides visibility into all deployed applications and dependencies without requiring extra code.
• The Azure Log Analytics workspace is the unified sink for all logs and metrics collected from Azure services and the application.

Configure the Azure Spring Apps instance to send diagnostics logs from the application to the provisioned Log Analytics workspace. For more information, see Monitor applications end-to-end.

Collect logs and metrics for other Azure services. The boot diagnostics is enabled for the jump box, so you can capture events as the virtual machine boots.

Configure diagnostic settings to send resource logs for all other Azure resources to a Log Analytics workspace. Resource logs aren't collected until they're routed to a destination. Each Azure resource requires its own diagnostic setting.

Data correlation from multiple workspaces

Logs and metrics generated by the workload and its infrastructure components are saved in the workload's Log Analytics workspace. However, logs and metrics generated by centralized services such as Active Directory and Azure Firewall are saved to a central Log Analytics workspace managed by platform teams. Correlating data from different sinks can lead to complexities.

Consider a scenario of a user flow where the workload has dependencies on the centralized services. Part of the data might be collected at the workload level and exported to the central Log Analytics workspace where it's correlated with platform logs.

However, other entries might only exist at the workload's workspace due to issues like data volume, format interoperability, or security constraints. Uncorrelated log entries that exist across two or more workspaces for a single user flow can make it more difficult to troubleshoot certain issues. These added complexities require the teams to work together to troubleshoot application incidents.

To help with this type of collaboration, familiarize yourself with the procedures set up by your organization. When a security incident occurs, the workload-level administrators might be asked to review their systems' logs for signs of malicious activity or provide copies of their logs to incident handlers for further analysis. When workload administrators are troubleshooting application issues, they might need help from platform administrators to correlate log entries from enterprise networking, security, or other platform services.

Health probes

Azure Application Gateway uses health probes to ensure incoming traffic is routed to responsive back-end instances. Azure Spring Apps Readiness, Liveness, and Startup probes are recommended. If there's a failure, these probes can help in graceful termination. For more information, see How to configure health probes.

Security considerations

The centralized teams provide networking and identity controls as part of the platform. However, the workload should have security affordances to reduce the attack surface. For more information, see Azure Spring Apps landing zone: Security.

Data at rest

Data at rest should be encrypted. The application itself is stateless. Any data is persisted in an external database, where this architecture uses Azure Database for MySQL. This service encrypts the data, including backups and temporary files created while running queries.

Data in transit

Data in transit should be encrypted. Traffic between the user's browser and Azure Application Gateway must be encrypted to ensure data remains unchanged during transit. In this architecture, Azure Application Gateway only accepts HTTPS traffic and negotiates TLS handshake. This check is enforced through NSG rules on the Application Gateway subnet. The TLS certificate is loaded directly during deployment.

Traffic from Application Gateway to the Azure Spring Apps instance is re-encrypted to ensure only secure traffic reaches the application. The Azure Spring Apps service runtime receives that traffic and acts as the TLS termination point. From that point, inter-service communication within the application isn't encrypted. However, communication with other Azure PaaS services and the service runtime occurs over TLS.

You can choose to implement end-to-end TLS communication through Azure Spring Apps. Consider the tradeoffs. There might be a negative effect on latency and operations.

Data in transit should be inspected for vulnerabilities. Web Application Firewall is integrated with Application Gateway and further inspects traffic blocking OWASP vulnerabilities. You can configure Web Application Firewall to detect, monitor, and log threat alerts. Or, you can set up the service to block intrusions and attacks detected by the rules.

DDoS protection

Distributed denial of service (DDoS) can take down a system by overburdening it with requests. Basic DDoS protection is enabled at the infrastructure level for all Azure services to defend against such attacks. Consider upgrading to Azure DDoS Protection service to take advantage of features such as monitoring, alerts, the ability set thresholds for the application. For more information, see Azure DDoS Protection Service frequently asked questions.

Secret management

Microsoft's Zero Trust security approach requires secrets, certificates, and credentials to be stored in a secure vault. The recommended service is Azure Key Vault.

There are alternate ways to store secrets depending on the Azure service and intent. This architecture implements the following approach:

• Certificates are loaded during deployment.
• The connection to MySQL is implemented by using Service Connector.

Cost optimization strategies

Because of the nature of distributed system design, infrastructure sprawl is a reality. This reality results in unexpected and uncontrollable costs. Azure Spring Apps is built by using components that scale to help meet demand and optimize cost. The foundation of this architecture is the Azure Kubernetes Service (AKS). The service is designed to reduce the complexity and operational overhead of managing Kubernetes and includes efficiencies in the operational cost of the cluster.

You can deploy different applications and application types to a single instance of Azure Spring Apps. The service supports autoscaling of applications triggered by metrics or schedules that can improve utilization and cost efficiency.

You can also use Application Insights and Azure Monitor to lower operational cost. With the visibility provided by the comprehensive logging solution, you can implement automation to scale the components of the system in real time. You can also analyze log data to reveal inefficiencies in the application code that you can address to improve the overall cost and performance of the system.

Scenario deployment

A deployment for this reference architecture is available in the Azure Spring Apps landing zone GitHub repository. The deployment uses Terraform templates.

The artifacts in this repository provide a foundation that you can customize for your environment. The implementation creates a hub network with shared resources such as Azure Firewall for illustrative purposes. This grouping can be mapped to separate landing zone subscriptions to keep workload and platform functions separate.

To deploy the architecture, follow the step-by-step instructions.

VMware support with the Enterprise tier

If you want managed VMware Tanzu® support for your live deployment, consider upgrading to the Azure Spring Apps Enterprise tier. The VMware Tanzu® Service Registry is integrated for Azure Spring Apps, which allows for service discovery and registration.

For gateway routing, you can switch to VMware Spring Cloud Gateway. It offers a feature set that includes authentication and authorization, resiliency features, and rate limiting.

In the Enterprise tier, Application Configuration Service for Tanzu® enables the management of Kubernetes-native ConfigMap resources that are populated from properties defined in one or more Git repositories.

There are other VMware services supported on this tier. For more information, see Enterprise tier in Azure Marketplace.

The reference implementation supports Azure Spring Apps Enterprise SKU as a deployment option. In this option, there are some architecture changes. It uses an instance of Azure Database for PostgreSQL flexible server deployed with Azure Virtual Network integration and Azure Cache for Redis with private endpoint. The sample application is Fitness Store app.

Next steps

• Review the design areas of the Azure Spring Apps landing zone guidance.

Related resources

For product documentation on the Azure services used in this architecture, see the following articles:

• Azure Spring Apps Enterprise
• Azure Application Gateway v2
• Azure Database for MySQL
• Azure Key Vault
• Azure Virtual Network
• Route tables

For other implementation scenarios, see the following articles:

• Deploy Azure Spring Apps to multiple regions
• Expose Azure Spring Apps through a reverse proxy