[Java知识库]SpringCloud之Ribbon路由、负载和熔断

1.服务ribbon-ha

application.yml

server:
  port: 8092

spring:
  application:
    name: ribbon-ha

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8088/eureka/

注入RestTemplate实现请求转发

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

对外提供接口

@RestController
public class HaController {

    @Autowired
    private HaService haService;

    @Value("${server.port}")
    private String port;

    @GetMapping("hello")
    public String hello(@RequestParam String name) {
        return "ha，" + name + " ! " + "访问端口号：" + port;
    }

    @GetMapping("ha")
    public String ha(@RequestParam String name) {
        return haService.callHi(name);
    }
}

@Service
public class HaService {

    @Autowired
    private RestTemplate restTemplate;

    public String callHi(String name) {
        return restTemplate.getForObject("http://ribbon-hi/hello?name=" + name, String.class);
    }
}

2.服务ribbon-hi

application.yml

server:
  port: 8093

spring:
  application:
    name: ribbon-hi

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8088/eureka/

@RestController
public class HiController {

    @Autowired
    private HiService hiService;

    @Value("${server.port}")
    private String port;

    @GetMapping("hello")
    public String hello(@RequestParam String name) {
        return "hi，" + name + " ! " + "访问端口号：" + port;
    }

    @GetMapping("hi")
    public String hi(@RequestParam String name) {
        return hiService.callHa(name);
    }
}

@Service
public class HiService {

    @Autowired
    private RestTemplate restTemplate;

    public String callHa(String name) {
        return restTemplate.getForObject("http://ribbon-ha/hello?name=" + name, String.class);
    }
}

3.路由转发

依次启动 eureka、ribbon-ha、ribbon-hi

访问
http://localhost:8092/hello?name=yzm
http://localhost:8093/hello?name=yzm


http://localhost:8092/ha?name=yzm
http://localhost:8093/hi?name=yzm


看得出8092的ha请求被转发到8093去了
看得出8093的hi请求被转发到8092去了

4.负载均衡

再启动一个ribbon-hi:18093服务

一直刷新访问
http://localhost:8092/ha?name=yzm

8092的请求以轮询的方式，分发给8093和18093

5.熔断降级

把8093、18093服务都关闭了
访问：http://localhost:8092/ha?name=yzm

直接显示错误信息不够友好又或者需要记录日志信息之类的，这个时候就可以进行熔断处理。

需要添加Hystrix依赖

        <!-- 熔断 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>

在启动类上加注解：@EnableHystrix 开启熔断降级功能

修改service

通过@HystrixCommand指定转发失败后，回调haError()方法

@Service
public class HaService {

    @Autowired
    private RestTemplate restTemplate;

    @HystrixCommand(fallbackMethod = "haError")
    public String callHi(String name) {
        return restTemplate.getForObject("http://ribbon-hi/hello?name=" + name, String.class);
    }

    public String haError(String name) {
        return "ha," + name + " , ribbon-hi 服务挂了!";
    }
}

@Service
public class HiService {

    @Autowired
    private RestTemplate restTemplate;

    @HystrixCommand(fallbackMethod = "hiError")
    public String callHa(String name) {
        return restTemplate.getForObject("http://ribbon-ha/hello?name=" + name, String.class);
    }

    public String hiError(String name) {
        return "hi," + name + " , ribbon-ha 服务挂了!";
    }
}

重新启动8092、8093
正常访问：http://localhost:8092/ha?name=yzm
关闭8093后再次访问

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