Section 2: API Gateway Service

API Gateway Service 개요
Netflix Ribbon과 Zuul
Spring Cloud Gateway - 기본
Spring Cloud Gateway - Filter
Spring Cloud Gateway - Eureka 연동
Spring Cloud Gateway - Load Balancer

API Gateway Service 개요

• 인증 및 권한 부여
• 서비스 검색 통합
• 응답 캐싱
• 정책, 회로 차단기 및 QoS 다시 시도
• 속도 제한
• 부하 분산
• 로깅, 추적, 상관 관계
• 헤더, 쿼리 문자열 및 청구 변환
• IP 허용 목록에 추가

Netflix Zuul 구현

• Spring Boot: 2.4.0 이하 에서 지원함. (최신 버전의 Spring Cloud Routing에서는 Zuul 지원하지 않음.)
• First Service, Second Service
  • Spring Boot: 2.3.8
  • Developer Tools: Lombok
  • Web: Spring Web
• Zuul Service
  • Spring Boot: 2.3.8
  • Web: Spring Web
  • Spring Cloud Routing: Zuul (API Gateway 역할) @EnableZuulProxy
    • ZuulFilter

Spring Cloud Gateway - 기본

• Developer Tools: Spring Boot DevTools
• Spring Cloud Discovery: Eureka Discovery Client
• Spring Cloud Routing: Gateway

Spring Cloud Gateway - Filter

• Filter using Java Code - FilterConfig.java

  @Configuration
  public class FilterConfig {
  
    @Bean
    public RouteLocator gatewayRoutes(RouteLocatorBuilder builder) {
        return builder.routes()
                .route(r -> r.path("/first-service/**")
                        .filters(f -> f.addRequestHeader("first-request", "first-request-header")
                                .addResponseHeader("first-response", "first-response-header"))
                        .uri("http://localhost:8081"))
                .route(r -> r.path("/second-service/**")
                        .filters(f -> f.addRequestHeader("second-request", "second-request-header")
                                .addResponseHeader("second-response", "second-response-header"))
                        .uri("http://localhost:8082"))
                .build();
    }
  }
  

• Filter using with application.yml
  • Configuration java 코드를 작성하지 않고 applicaiton.yml 설정 만으로도 가능함.

spring:
  application:
    name: apigateway-service
  cloud:
    gateway:
      routes:
        - id: first-serivce
          uri: http://localhost:8081
          predicates:
            - Path=/first-service/**
          filters:
            - AddRequestHeader=first-request, first-request-header2
            - AddResponseHeader=first-response, first-response-header2
        - id: second-serivce
          uri: http://localhost:8082
          predicates:
            - Path=/second-service/**
          filters:
            - AddRequestHeader=second-request, second-request-header2
            - AddResponseHeader=second-response, second-response-header2

• Custom Filter
  • 사용자 필터를 구현하고 application.yml에서 필터가 필요한 routes 에 설정한다.

@Component
@Slf4j
public class CustomFilter extends AbstractGatewayFilterFactory<CustomFilter.Config> {

    public CustomFilter() {
        super(Config.class);
    }

    @Override
    public GatewayFilter apply(Config config) {
        // Custom Pre Filter
        return ((exchange, chain) -> {
            ServerHttpRequest request = exchange.getRequest();
            ServerHttpResponse response = exchange.getResponse();

            log.info("Custom PRE filter: request id -> {}", request.getId());

            // Custom Post Filter
            return chain.filter(exchange).then(Mono.fromRunnable(() -> {
                log.info("Custom POST filter: request id -> {}", response.getStatusCode());
            }));
        });
    }

    public static class Config {

    }
}

spring:
  application:
    name: apigateway-service
  cloud:
    gateway:
      routes:
        - id: first-serivce
          uri: http://localhost:8081
          predicates:
            - Path=/first-service/**
          filters:
#            - AddRequestHeader=first-request, first-request-header2
#            - AddResponseHeader=first-response, first-response-header2
            - CustomFilter
        - id: second-serivce
          uri: http://localhost:8082
          predicates:
            - Path=/second-service/**
          filters:
#            - AddRequestHeader=second-request, second-request-header2
#            - AddResponseHeader=second-response, second-response-header2
            - CustomFilter

• Global Filter
  • Global Filter를 구현하고 applicatin.yml에 default-filters를 설정한다.
• Logging Filter
  • 차이점을 모르겠군. ㅡㅡ;

@Component
@Slf4j
public class LoggingFilter extends AbstractGatewayFilterFactory<LoggingFilter.Config> {

    public LoggingFilter() {
        super(Config.class);
    }

    @Override
    public GatewayFilter apply(Config config) {
//        return ((exchange, chain) -> {
//            ServerHttpRequest request = exchange.getRequest();
//            ServerHttpResponse response = exchange.getResponse();
//
//            log.info("Global baseMessage: {}", config.getBaseMessage());
//
//            if (config.isPreLogger()) {
//                log.info("Global Filter Start: request id -> {}", request.getId());
//            }
//
//            return chain.filter(exchange).then(Mono.fromRunnable(() -> {
//                if (config.isPostLogger()) {
//                    log.info("Global Filter End: response id -> {}", response.getStatusCode());
//                }
//            }));
//        });

        GatewayFilter filter = new OrderedGatewayFilter((exchange, chain) -> {
            ServerHttpRequest request = exchange.getRequest();
            ServerHttpResponse response = exchange.getResponse();

            log.info("Logging Filter baseMessage: {}", config.getBaseMessage());

            if (config.isPreLogger()) {
                log.info("Logging PRE Start: request id -> {}", request.getId());
            }

            return chain.filter(exchange).then(Mono.fromRunnable(() -> {
                if (config.isPostLogger()) {
                    log.info("Logging POST End: response id -> {}", response.getStatusCode());
                }
            }));
        }, Ordered.HIGHEST_PRECEDENCE);

        return filter;
    }

    @Data
    public static class Config {
        private String baseMessage;
        private boolean preLogger;
        private boolean postLogger;

    }
}

Spring Cloud Gateway - Eureka 연동

• Eureka Server: discovery service
• Eureka Client: APIGATEWAY-SERVICE, MY-FIRST-SERVICE, MY-SECOND-SERVICE

Spring Cloud Gateway - Load Balancer

• uri에 port를 명시하지 않고 Load Balancer를 통하도록 한다.

      routes:
        - id: first-serivce
#          uri: http://localhost:8081
          uri: lb://MY-FIRST-SERVICE

• First Service, Second Service를 각 2개씩 기동
  • 궁극적으로 Random Port를 이용하는 방식으로 Load Balancer를 통하도록 한다. 방법1,2,3)은 참고만 하자.
  • 방법1) VM Options -> -Dserver.port=[다른포트]
  • 방법2) $ mvn spring-boot:run -Dspring-boot.run.jvmArguments='-Dserver.port=9003'
  • 방법3)

    $ mvn clean compile package
    $ java -jar -Dserver.port=9004 ./target/user-service-0.0.1-SNAPSHOT.jar
    

  • 방법4) Random Port 설정한다. 첫번째는 Intellij에서 Run, 두번째는 Terminal에서 포트 지정 없이 application 구동 $ mvn spring-boot:run

server:
  port: 0  #random port

spring:
  application:
    name: my-first-service

eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://localhost:8761/eureka
  instance:  #랜덤포트 설정 시 Eureka Server에서 port가 0으로 모두 표시되므로 각각을 구별하기 위해 다음처럼 설정한다.
    instance-id: ${spring.application.name}:${spring.application.instance_id:${random.value}}