Eureka Registry

基于RestTemplate发起的http请求实现远程调用

@SpringBootApplication
public class OrderApplication {
    
    public static void main(String[] args) {
    
        SpringApplication.run(OrderApplication.class, args);
    }
    @Bean
    public RestTemplate restTemplate(){
    
        return new RestTemplate();
    }
}

@Service
public class OrderService {
    
    @Autowired
    private OrderMapper orderMapper;
    @Autowired
    private RestTemplate restTemplate;

    public Order queryOrderById(Long orderId) {
    
        // 1.查询订单
        Order order = orderMapper.findById(orderId);
        // 2.使用RestTemplate发起Http请求,实现远程调用
        // Deserialize the result of the response to User对象
        String url = "http://localhost:8081/user/" + order.getUserId();
        User user = restTemplate.getForObject(url, User.class);
        // 3.填充
        order.setUser(user);
        // 4.返回
        return order;
    }
}

Eureka注册中心

Every time the service starts, it will be thereEurekaRegistration center for registration information.
Consumer调用Provider的时候,It will be pulled from the registry,Provider的注册信息.
Every service every other30s都会向EurekaSend a heartbeat request,报告健康状态,If you don't jump,EurekaIts registration information will be deleted.

搭建Eureka注册中心

新建一个maven模块,添加依赖

        <!-- eureka服务端 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
            <!-- The version numbers need to matchspring-cloud-dependenciesin dependency managementnetflix版本 -->
            <version>3.0.3</version>	
        </dependency>

启动类

@EnableEurekaServer
@SpringBootApplication
public class EurekaApplication {
    
    public static void main(String[] args) {
    
        SpringApplication.run(EurekaApplication.class,args);
    }
}

配置文件

server:
  port: 10086

spring:
  application:      # 服务名称
    name: eureka_server

eureka:
  client:
    service-url:  # eurekaown address information (eurekaYou will also register your own information)
      defaultZone:  http://localhost:10086/eureka

启动该模块,You can see this information

Eureka服务注册

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            <version>3.0.3</version>
        </dependency>

spring:
  application:
    name: orderService		# 服务名称不能使用下划线
eureka:
  client:
    service-url:
      defaultZone: http://localhost:10086/eureka

Eureka服务拉取

Pull based on service name

    public Order queryOrderById(Long orderId) {
    
        // 1.查询订单
        Order order = orderMapper.findById(orderId);
// String url = "http://localhost:8081/user/" + order.getUserId();
// 将IPThe address and port number are changed to the service name
        String url = "http://userService/user/" + order.getUserId();
        User user = restTemplate.getForObject(url, User.class);
        // 3.填充
        order.setUser(user);
        // 4.返回
        return order;
    }

    @Bean
    @LoadBalanced
    public RestTemplate restTemplate(){
    
        return new RestTemplate();
    }

实现原理：
After the request is made, it will be receivedLoadBalancerInterceptorIntercepted by load balancing interceptors,Extract the service name to handRibbonLoadBalancerClient处理.
RibbonLoadBalancerClientBy service name fromDynamicServerListLoadBalancer中获取真实的IPList of address port numbers,再依据IRule
负载均衡策略,to choose a final one.
调整负载均衡策略：
第一种方式：作用是全局的

@Bean
public IRule randomRule(){
    
	return new RandomRule();
}

第二种方式：针对某个服务

userService:
	ribbon:
		NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule	

Ribbon默认采用懒加载,It is only created on the first visitLoadBalanceClient,The request time will be longer.
饥饿加载会在项目启动时创建,降低第一次访问的耗时

ribbon:
	eager-load:
		enabled: true
		clients: userService		# 针对的服务