An option with having asynchronous communication is that you can increase the number of instances of the SMSService. Suppose, on any given day, that there is a need to send out 100,000 SMS messages. It can then send out the SMS messages for all its pending requests. When the SMSService comes back up, it will find the order event and process it. However, in the second approach, called asynchronous communication, the order request is placed on the queue. Failure of one of the components would lead to cancellation of the customer request, with a need for him to re-initiate the order - at a later point in time. That might mean canceling the order, as all steps are part of a single transaction. In Option 1, since the OrderService directly invokes the SMSService on receiving an order, an SMS cannot be sent out. Let's say the SMSService is down for a short time. Let's look at the advantages of using asynchronous communication based on a messaging queue. That's when you go for the second approach, of bringing a queue in. However, when we talk of a large scale e-commerce web applications, such as, that receive millions of orders in a short time, you need a lot of flexibility. The first architecture might be all you need. If your business goal is to support a few hundreds or thousands of users, then a simple architecture would be a good choice. The PackageService does the required package processing on the item.The SMSService sends out an SMS to the user.The EmailService sends out an email to the customer.The StockService processes the order and updates the database.The rest of the components are independent services, listening on the Queue.Īs soon as an order is placed on the queue: When the OrderService receives an order, it places the request on the Queue. The other option is to have a queue in-between the receiving OrderService component, and the rest of the components. Option 2: Introducing Asynchronous Messaging Using Queues For example, write a Java class which accepts the order, and does all of the processing itself. One way to design this application would be to have a single component that accomplishes all this functionality. Option 1: Single Component for All Processing Call the PackageService to start delivery.Send communication to the user through the EmailService and SMSService.

It needs to send a request to the StockService.

Microservices Best Practices: Why Do You Build a Vertical Slice?Ĭonsider the simple example of an ordering service:Ī customer places an order through the OrderService. Microservices Architectures: Event Driven Approach The 12 Factor App: Best Practices in Cloud Native Applications and Microservices This is the fourth article in a series of six articles on best practices with cloud and microservices. What are the advantages of using Queues in microservices architectures?īest Practices With Cloud and Microservices.What is asynchronous communication or asynchronous messaging?.In this article, we discuss why queues are needed, and how they form the cornerstone of asynchronous communication in microservices architectures.

Message queue architecture