book-microservices-v2 / chapter07

Learn Microservices with Spring Boot (2nd edition) - Chapter 7

Learn Microservices with Spring Boot - Chapter 7

This repository contains the source code of the practical use case described in the book Learn Microservices with Spring Boot (2nd 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.

Chapter 7 version

In Chapter 7, you learn how to achieve loose coupling with an Event-Driven Architecture using a RabbitMQ message broker. Besides, you go through the extra advantages like the ability to implement different messaging patterns, load balancing, and resilience.

The main concepts included in this chapter are:

• Event-Driven Architectures: Pros and Cons
• Embracing Eventual Consistency, all the way up to the UI
• RabbitMQ main concepts, messaging patterns, and practical implementation
• Refactoring the microservices towards an Event-Driven strategy
• Resilience with persistent messages

As usual, the book uses this practical implementation to teach you why introducing a message broker between our microservices is a good idea. You learn the patterns before the tools, so you can use your knowledge to build similar architectures using a different technology stack - e.g. Kafka.

Check the Book's Web Page to see the complete list of chapters.

Running the app

Requirements:

• JDK 14+
• Node.js v13.10+
• npm 6.13.7+
• RabbitMQ 3.8.3+

1. You need a RabbitMQ server running. Run the server according to the instructions for your OS, for example:

   $ rabbitmq-server

2. To start the Multiplication microservice, you can use the command line with the included Maven wrapper:

   multiplication$ ./mvnw spring-boot:run

3. To start the Gamification microservice, you do the same from its corresponding folder:

   gamification ./mvnw spring-boot:run

4. The React application can be started with npm. First, you need to download the dependencies with:

   challenges-frontend$ npm install

5. Then, you start the server with:

   challenges-frontend$ npm start

Once the backend and the fronted are started, you can navigate to http://localhost:3000 in your browser and start resolving multiplication challenges. This time, you'll see the Leaderboard.

Questions

• 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.

About the book

Are you interested in building a microservice architecture from scratch? You'll face all the challenges of designing and implementing a distributed system one by one, and will be able to evaluate if it's the best choice for your project.

Visit https://tpd.io/book-extra for all the details about the book.

Purchase

You can buy the book online from these stores:

• Apress
• Amazon
• and other online stores, check the IBAN (9781484261309) on google

Source code by chapter (all repositories are available on Github)

• Chapter 3. A professional 3-tier 3-layer Spring Boot app
• Chapter 4. Building a basic frontend in React (backender-friendly)
• Chapter 5. The Data Layer Concepts and Spring Data JPA
• Chapter 6. Starting with Microservices - Synchronous
• Chapter 7. Event-Driven Architectures - Making our system asynchronous
• Chapter 8 (I). The Gateway Pattern in Microservice Architectures (Spring Cloud Gateway)
• Chapter 8 (II). Service Discovery and Load Balancing for Spring Boot Microservices (Consul / Spring Cloud Load Balancer)
• Chapter 8 (III). Centralized Configuration with Consul KV
• Chapter 8 (IV). Centralized Logs, Distributed Tracing, and Containerization with Docker (Buildpacks) and Docker Compose

Extra chapters:

• E.1. End-to-End Microservice tests with Cucumber
• U.2.4.0. Upgrade: Spring Boot 2.4.0, Cloud 2020.0, Java 15

chapter07's Issues

H2 Database - Feature not supported: "AUTO_SERVER=TRUE && DB_CLOSE_ON_EXIT=FALSE"

When following the instructions to run multiple instances of the multiplication and gamification service I encountered the following issue: This feature is not supported: "AUTO_SERVER=TRUE && DB_CLOSE_ON_EXIT=FALSE"

How to resolve this problem?

Wrong image reference

On page 277 there is a paragraph that goes:

Follow the same steps as in previous scenarios to boot up one instance of each
microservice, the UI, and the RabbitMQ service. Then, run the commands in Listing 7-21
in two separate terminals to have the same setup as shown in the previous Figure 7-23,
with two replicas of each microservice. Keep in mind that you need to execute them from
each corresponding microservice’s home folder.

The "same setup as shown in the previous Figure 7-23" part is wrong. It should be pointing to Figure 7-24.

GameServiceImpl

Hi, i'm reading your book and changed the version of spring to 3.1.6 with Java 17, I had this issues
'map(java.util.function.Function<? super com.killer.gamification.domain.BadgeType,? extends R>)' in 'java.util.stream.Stream' cannot be applied to '()' in the processForBadges method. Can you give me some advice?

Set alreadyGotBadges;
alreadyGotBadges = badgeRepository
.findByUserIdOrderByBadgeTimestampDesc(solvedChallenge.getUserId())
.stream()
.map(BadgeCard::getBadgeType)
.collect(Collectors.toSet());

Test GameEventHandler

Hi, in your book, you recommend creating a test for a new Game Event Handler class. You have an implementation of this test, because I'm a little confused about how to use this instruction to create a test for the consumer https://docs.spring.io/spring-amqp/reference/html/#test-harness

Call verify method on the void method?

Does it need to call the verify method on a void method?

chapter07/multiplication/src/test/java/microservices/book/multiplication/challenge/ChallengeServiceTest.java

Line 57 in 9ef2931

verify(eventPub).challengeSolved(resultAttempt);