Chapter 3. Integration Techniques

In the previous chapter, we developed microservices using a .NET monolithic application. These services are independent of each other and are located on different servers. What would be a better way to have inter-service communication, where one service interacts/communicates with the other? In this chapter, we will discuss the various patterns and ways that will help us foster this communication. We will cover the following topics:

• Communication between services
• Styles of collaborations
• Integration patterns
• The API gateway
• The event-driven pattern
• Azure Service Bus

Communication between services

In the case of a .NET monolithic application, if there is a need to access third-party components or external services, we use the HTTP client or another client framework to access the resources. In Chapter 2, Building Microservices, we developed Product service in such a way that it would work independently. But this was not the case; we mandatorily required a few services to interact with each other. So this is a challenge: having services communicate with each other. Both Product service and Order service are hosted on separate servers. Both these servers are independent of each other, are based on REST, and have their own endpoints via which they communicate with each other (when a service interacts with another service and vice versa, we refer to it as inter-service communication as well).

There are ways in which services communicate with each other; let's discuss them briefly:

• Synchronous: In this, the client makes a request to the remote service (called...

Integration patterns

Until now, we have discussed inter-service communication and have gone through the practical implementation of Product service with the use of synchronous and asynchronous communication. We've also implemented microservices using different styles of collaborations. Our FlixOne bookstore (developed as per the microservice architectural style) required more interaction; therefore, it required more patterns. In this section, we will discuss the implementation of various integration patterns required for our application.

Note

The complete application of the FlixOne bookstore is available in Chapter 10, Creating a Complete Microservice Solution.

The API gateway

In the styles of collaboration section, we discussed two styles using which we can foster intercommunication between microservices. Our application is spread into various microservices:

• Product service
• Order service
• Invoice service
• Customer service

In our FlixOne bookstore (user interface), we need to show a few details:

• Book...

Summary

Inter-service communication is possible with synchronous or asynchronous communication, which are styles of collaborations. Microservices should have asynchronous APIs. The API gateway is a proxy server that provides a way to interact various clients with APIs. API management, as an API gateway, provides plenty of features to manage/host various RESTful APIs. There are various patterns that help us communicate with microservices. With the use of Azure Bus Service, we can easily manage and play with inter-service communication using the Azure Bus Service message queue; services can easily send or receive messages from each other through this. Eventual consistency talks about scalable systems with high scalability, and it is proven with the CAP theorem. 

In the next chapter, we will discuss various testing strategies to test an application and build on the microservice architectural style.