Spring Boot Microservice example

Spring Boot 2.x example how to create small project with microservice architecture

Description

Spring Boot 2.7.6, REST API, RestTemplate, Spring Cloud 2021.0.5, Eureka server, Actuator, Resilience4j

Dependencies

• Java 11
• Gradle
• Build and run with Java 11
• You can registrate in https://www.themoviedb.org page

sudo update-alternatives --config java (select Java 11) 

Components

Service Discovery

• Use Netflix Eureka service registry to use client side load balancing and decouples service providers

Installing

• Build application

gradle clean bootjar

Running

java -jar service-discovery-1.0.0.jar

Testing

• View the administrator UI the following URL

http://localhost:8787/

Rating Service

• Get rating information of the selected movie

Installing

• Build application

gradle clean bootjar

Running application (in two instances)

java -jar -Dserver.port=8083 rating-service-1.0.0.jar
java -jar -Dserver.port=8084 rating-service-1.0.0.jar

Testing

• You can see two "rating-service" instance in Eureka admin UI

• You can check the Actuator health endpoints

http://192.168.0.105:8083/actuator/health
http://192.168.0.105:8084/actuator/health

• Get movie rating summary data by movie ID

http://192.168.0.105:8083/ratingsdata/1234

• Get user ratings list by user ID

http://192.168.0.105:8083/ratingsdata/users/9876

Movie Info Service

• Get description of the selected movie via "api.themoviedb.org"

Installing

• Build application

gradle clean bootjar

Running

java -jar movie-info-service-1.0.0.jar

Testing

• You can see the "movie-info-service" in Eureka admin UI

• You can check the Actuator health endpoint

http://192.168.0.105:8082/actuator/health

• Get sample movie description

http://192.168.0.105:8082/movies/1234

Movie Catalog Service

• Get movie catalog list with ratings (from rating-service), use service discovery and Resilience4J

Installing

• Build application

gradle clean bootjar

Running

java -jar movie-catalog-service-1.0.0.jar

Testing

• You can see the "movie-catalog-service" in Eureka admin UI

• You can check the Actuator health endpoint

http://192.168.0.105:8081/actuator/health

• Get sample configuration parameters (from application.properties)

http://192.168.0.105:8081/catalog/config

• Get user ratings aggregate information (call movie-rating-service after that call movie-info-service)

http://192.168.0.105:8081/catalog/1234

• Some words how to use Resilience4J

application.yaml (extract)

resilience4j:
  circuitbreaker:
    instances:
      ratingService:
        registerHealthIndicator: true
        eventConsumerBufferSize: 10
        failureRateThreshold: 50
        minimumNumberOfCalls: 5
        automaticTransitionFromOpenToHalfOpenEnabled: true
        waitDurationInOpenState: 5s
        permittedNumberOfCallsInHalfOpenState: 3
        slidingWindowSize: 10
        slidingWindowType: COUNT_BASED
  retry:
    instances:
      ratingService:
        maxAttempts: 3
        waitDuration: 10000
  bulkhead:
    instances:
      ratingService:
        maxWaitDuration: 5000
        maxConcurrentCalls: 5

• You can use Resilience4J annotations in source code (com.example.movie.resources.MovieCatalogResource class):

  • Circuit Breaker

    @CircuitBreaker(name = "ratingService", fallbackMethod = "fallbackMethodForRatingService")
    ...
    ...
    public ResponseEntity<String> fallbackMethodForRatingService(Exception exception) {
        return ResponseEntity.status(HttpStatus.GATEWAY_TIMEOUT).body("This is the fallback method!");
    }
    

  • Retry

    @Retry(name = "ratingService", fallbackMethod = "retryMethodForRatingService")
    ...
    ...
    public ResponseEntity<String> retryMethodForRatingService(Exception exception) {
      return ResponseEntity.status(HttpStatus.NOT_FOUND).body("This is the retry method!");
    }
    

  • Bulkhead

    @Bulkhead(name = "ratingService", fallbackMethod = "bulkHeadMethodForRatingService")
    ...
    ...
    public ResponseEntity<String> bulkHeadMethodForRatingService(Exception exception) {
        return ResponseEntity.status(HttpStatus.NOT_FOUND).body("This is the bulkhead method!");
    }
    

Author

Kenyeres Géza https://hu.linkedin.com/in/g%C3%A9za-kenyeres-17341631