This repository contains the source code of the practical use case described in the book Learn Microservices with Spring Boot 3 (3rd Edition). The book follows a pragmatic approach to building a Microservice Architecture. You start with a small monolith and examine the pros and cons that come with a move to microservices.
The Chapter 8's source code is divided into four parts for a better understanding of how the system evolves when we start introducing Common Patterns in Microservice Architectures.
In this second part, we introduce Service Discovery and Load Balancing, supported by the microservices' health checks. These patterns allow us to scale up our system, and to make it more resilient.
The main concepts included in this first part of the chapter are:
- Why do we need Service Discovery, a Load Balancer and a Health endpoint? The problems, explained.
- Basic concepts: Client-Side vs. Server-Side Discovery, Load Balancers, the Service Registry, detecting unhealthy instances, etc.
- Spring Cloud integrations: Spring Cloud Consul, Spring Cloud Actuator, Spring Cloud Load Balancer.
- Retry patterns and resilience using the Service Registry.
- Verifying how the system keeps working under chaos.
As usual, the book follows a hands-on approach, so you learn everything based on this microservice case study.
Requirements:
- JDK 17
- Node.js v18.16.0
- npm 9.7.1
- RabbitMQ 3.12.2
- Consul 1.16.0
- You need a RabbitMQ server running. Run the server according to the instructions for your OS, for example:
$ rabbitmq-server
- You also need Consul up and running (in development mode). Follow the instructions for your OS, for example:
$ consul agent -node=learnmicro -dev
- To start the Multiplication microservice, you can use the command line with the included Maven wrapper:
multiplication$ ./mvnw spring-boot:run
- To start the Gamification microservice, you do the same from its corresponding folder:
gamification$ ./mvnw spring-boot:run
- To start the Gateway microservice, you do the same from its corresponding folder:
gateway$ ./mvnw spring-boot:run
- The React application can be started with npm. First, you need to download the dependencies with:
challenges-frontend$ npm install
- Then, you start the server with:
challenges-frontend$ npm start
Note:
In the final version of our code, we use Docker to start our complete system easily. However, it's not yet introduced at this point in the book, so we're starting all these components manually.
Once the backend and the fronted are started, you can navigate to http://localhost:3000 in your browser and start resolving multiplication challenges.
Run the following command from your terminal or command line window:
$ http :8080/actuator/healthOpen terminal or command line window in your system and type the following command:
$ http -b :8500/v1/agent/servicesStarting with this version, you can try some interesting scenarios. For example, you can start a second instance of both the Multiplication and Gamification microservices, and then start killing some of these application processes. You'll see how Consul detects these failing services, and also how the Retry pattern in the Gateway makes everything work under failures.
To start a second instance of a microservice, you can use for example:
multiplication$ ./mvnw spring-boot:run -Dspring-boot.run.arguments="--server.port=9080"To kill an instance, you can use kill -9 for example, followed by the process id of the Java application (that you can find also in the Spring Boot app logs).
- Do you have questions about how to make this application work?
- Did you get the book and have questions about any concept explained within this chapter?
- Have you found issues using updated dependencies?
Don't hesitate to create an issue in this repository and post your question/problem there.
You can buy the book online from these stores: