This architecture is based on the basic enterprise integration architecture but includes how to integrate enterprise back-end systems. This architecture uses message brokers and events to decouple services for greater scalability and reliability. Ensure that you're familiar with the design and components in the basic integration architecture. These elements provide foundational information about the core components of this architecture.
Architecture
The back-end systems that this design references include software as a service (SaaS) systems, Azure services, message-based services, and existing web services in your enterprise.
Download a Visio file of this architecture.
Scenario details
The preceding architecture builds on the simpler basic enterprise integration architecture that uses Azure Logic Apps to orchestrate workflows directly with back-end systems and uses Azure API Management to create catalogs of APIs.
This version of the architecture adds two components that help make the system more reliable and scalable:
Azure Service Bus is a secure, reliable message broker.
Azure Event Grid is an event-routing service. It uses a publish and subscribe eventing model.
This architecture uses asynchronous communication via a message broker instead of making direct, synchronous calls to back-end services. Asynchronous communication provides the following advantages:
Uses the Queue-Based Load Leveling pattern to handle bursts in workloads via load-leveling
Uses the Publisher-Subscriber pattern so that you can broadcast messages to multiple consumers
Tracks the progress of long-running workflows reliably, even when they involve multiple steps or multiple applications
Helps to decouple applications
Integrates with existing message-based systems
Provides the ability to queue messages when a back-end system isn't available
Use Event Grid so that various components in the system can react to events when they happen, rather than relying on polling or scheduled tasks. Similar to a message queue and topics, Event Grid helps decouple applications and services. If an application or service publishes events, any interested subscribers are notified. You can add new subscribers without updating the sender.
Many Azure services support sending events to Event Grid. For example, a logic app can listen for an event when new files are added to a blob store. This pattern creates reactive workflows in which uploading a file or putting a message on a queue starts a series of processes. The processes might run in parallel or in a specific sequence.
Recommendations
Consider the following recommendations. For more recommendations, see Basic enterprise integration architecture.
Service Bus
Service Bus has two delivery models, the pull model and the proxied push model:
Pull model: The receiver continuously polls for new messages. If you need to manage multiple queues and polling times, polling might be inefficient. But this model can simplify your architecture because it removes extra components and data hops.
Proxied push model: The receiver initially subscribes to a specific event type on an Event Grid topic. When a new message is available, Service Bus raises and sends an event through Event Grid. This event then triggers the receiver to pull the next batch of messages from Service Bus. This model allows systems to receive messages almost in real time but without using resources to continuously poll for new messages. This architecture uses extra components that you must deploy, manage, and secure.
When you create a Standard Logic Apps workflow that consumes Service Bus messages, we recommend that you use the Service Bus built-in connector triggers. The built-in connector triggers abstract most of the pull model configuration without adding extra cost. This capability provides the right balance between cost, surface area management, and security because the connector continuously loops within the Logic Apps runtime engine. For more information, see Service Bus built-in connector triggers.
Use PeekLock mode to access a group of messages. When you use PeekLock, the logic app can perform steps to validate each message before completing or abandoning the message. This approach prevents accidental message loss.
Event Grid
When an Event Grid trigger fires, it means that at least one event happened. For example, when a logic app gets an Event Grid trigger for a Service Bus message, there might be several messages available to process.
Considerations
These considerations implement the pillars of the Azure Well-Architected Framework, which is a set of guiding tenets that can be used to improve the quality of a workload. For more information, see Microsoft Azure Well-Architected Framework.
Reliability
Reliability ensures your application can meet the commitments you make to your customers. For more information, see Design review checklist for Reliability.
Microsoft Entra ID is a globally distributed, highly available SaaS platform.
You can deploy API Management in several highly available configurations, according to business requirements and cost tolerance. For more information, see Ensure API Management availability and reliability.
The Logic Apps Consumption tier supports geo-redundant storage. For more information, see Business continuity and disaster recovery for Logic Apps.
Event Grid resource definitions for topics, system topics, domains, and event subscriptions and event data are automatically replicated across availability zones in a region. When there's a failure in one of the availability zones, Event Grid resources automatically fail over to another availability zone without any human intervention. For more information, see Cross-region disaster recovery and business continuity.
Service Bus Premium supports geo-disaster recovery and availability zones. Service Bus Standard supports replication.
For information about guaranteed availability details of each service, see SLAs for online services.
Security
Security provides assurances against deliberate attacks and the abuse of your valuable data and systems. For more information, see Design review checklist for Security.
To help secure Service Bus, pair Microsoft Entra authentication with managed identities. Microsoft Entra ID integration for Service Bus resources provides Azure role-based access control (RBAC) for fine-grained control over a client's access to resources. You can use Azure RBAC to grant permissions to a security principal, such as a user, a group, or an application service principal. The application service principal in this scenario is a managed identity.
If you can't use Microsoft Entra ID, use shared access signature (SAS) authentication to grant users access and specific rights to Service Bus resources.
If you need to expose a Service Bus queue or topic as an HTTP endpoint, for example, to post new messages, use API Management to help secure the queue by fronting the endpoint. You can then use certificates or OAuth authentication to help secure the endpoint. The easiest way to help secure an endpoint is to use a logic app that has an HTTP request or response trigger as an intermediary.
The Event Grid service helps secure event delivery through a validation code. If you use Logic Apps to consume the event, validation is automatic. For more information, see Event Grid security and authentication.
Network security
Consider network security throughout your design.
You can bind Service Bus Premium to a virtual network subnet service endpoint. This configuration helps secure the namespace because it only accepts traffic from authorized virtual networks. You can also use Azure Private Link to only allow private traffic to your virtual network via private endpoints.
You can configure Logic Apps Standard and Premium to accept inbound traffic through private endpoints and to send outbound traffic through virtual network integration.
You can use an Azure virtual network to help secure access to your API Management instance and APIs. This method supports private endpoints. For more information, see Use a virtual network with API Management.
Cost Optimization
Cost Optimization is about looking at ways to reduce unnecessary expenses and improve operational efficiencies. For more information, see Design review checklist for Cost Optimization.
Use the Azure pricing calculator to estimate costs. Here are some other considerations.
API Management
You're charged for all API Management instances when they run. If you scale up, and then you no longer need that level of performance, manually scale down or configure autoscaling.
For light usage workloads, consider the Consumption tier, which is a low-cost, serverless option. The Consumption tier is billed per API call. Other tiers are billed per hour.
Logic Apps
Logic Apps uses a serverless model. Billing is calculated based on the number of actions and connector calls. For more information, see Logic Apps pricing.
Service Bus queues, topics, and subscriptions
Service Bus queues and subscriptions support both proxied push and pull models to deliver messages. In the pull model, every polling request is metered as an action. Even if you set long polling to the default of 30 seconds, cost can be high. Unless you need real-time message delivery, consider using the proxied push model.
Service Bus queues are included in all tiers: Basic, Standard, and Premium. Service Bus topics and subscriptions are available in Standard and Premium tiers. For more information, see Service Bus pricing.
Event Grid
Event Grid uses a serverless model. Billing is calculated based on the number of operations. Operations include events that go to domains or topics, advanced matches, delivery attempts, and management calls. Usage of up to 100,000 operations is free of charge.
For more information, see Event Grid pricing and Well-Architected Framework Cost Optimization.
Operational Excellence
Operational Excellence covers the operations processes that deploy an application and keep it running in production. For more information, see Design review checklist for Operational Excellence.
The basic enterprise integration reference architecture provides guidance about DevOps patterns, which align to the Well-Architected Framework Operational Excellence pillar.
Automate recovery operations as much as possible to help improve operational excellence. With automation in mind, you can combine Azure log monitoring with Azure Automation to automate the failover of your Service Bus resources. For an example of automation logic to initiate a failover, see Failover flow.
Performance Efficiency
Performance Efficiency is the ability of your workload to scale to meet the demands placed on it by users in an efficient manner. For more information, see Design review checklist for Performance Efficiency.
To achieve higher scalability, the Service Bus Premium tier can scale out the number of messaging units. For more information, see Service Bus Premium and Standard messaging tiers and Autoscaling feature.
For more Service Bus recommendations, see Best practices for performance improvements by using Service Bus messaging.
Next steps
- Service Bus to Event Grid integration overview
- Tutorial that uses messaging to integrate non-Microsoft systems via NServiceBus