OpenFeign集成Sentinel实现服务的熔断降级

引入依赖

Feign 适配整合在 Spring Cloud Alibaba 中，所以我们直接引入spring cloud alibaba中的组件就好

<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
</dependency>

除此之外，我们还需要引入OpenFeign和Nacos的依赖

        <!--添加loadbalancer依赖
            由于 Netflix Ribbon 进入停更维护阶段，因此 SpringCloud 2020.0.1 版本之后 删除了eureka中的ribbon，
            替代ribbon的是spring cloud自带的LoadBalancer，默认使用的是轮询的方式
            新版本的 Nacos discovery 都已经移除了 Ribbon ，此时我们需要引入 loadbalancer 代替，才能调用服务提供者提供的服务
        -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

生产者接口

在配置消费者之前，我们需要先编写好生产者的相关代码，这里引用之前的user-service，不再赘述，只贴出一些核心代码，完整的源码可以在gitee或者github上找到，文末会给出仓库地址

package cuit.epoch.pymjl.controller;
​
import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import cuit.epoch.pymjl.entity.User;
import cuit.epoch.pymjl.exception.AppException;
import cuit.epoch.pymjl.result.CommonResult;
import cuit.epoch.pymjl.result.ResultUtils;
import cuit.epoch.pymjl.service.UserService;
import lombok.extern.log4j.Log4j2;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
​
import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.concurrent.atomic.AtomicInteger;
​
/**
 * @author Pymjl
 * @version 1.0
 * @date 2022/8/25 12:48
 **/
@RestController
@RequestMapping("/user")
@Log4j2
public class UserController {
    private static final AtomicInteger ATOMIC_INTEGER = new AtomicInteger(0);
​
    @Resource
    UserService userService;
​
    @Value("${server.port}")
    private String port;
​
    @GetMapping("/test")
    @SentinelResource(value = "test", blockHandler = "handleTest")
    public CommonResult<String> test(HttpServletRequest request) throws UnknownHostException {
        System.out.printf("被[/%s:%s]调用了一次%n", request.getRemoteHost(), request.getRemotePort());
        String hostAddress = InetAddress.getLocalHost().getHostAddress() + ":" + port;
        return ResultUtils.success(hostAddress);
    }
​
    @GetMapping("/register")
    @SentinelResource("register")
    public CommonResult<String> register() {
        userService.register();
        return ResultUtils.success();
    }
​
    @GetMapping("/get/{id}")
    @SentinelResource(value = "getUser")
    public CommonResult<User> get(@PathVariable("id") Long id) {
        int cnt = ATOMIC_INTEGER.incrementAndGet();
        log.info("cnt=={}", cnt);
        if (cnt % 2 == 0) {
            throw new AppException("发生了异常");
        }
        return ResultUtils.success(userService.get(id));
    }
​
    public CommonResult<String> handleTest(HttpServletRequest request, BlockException blockException) {
        log.error("调用/user/test失败");
        return ResultUtils.fail("Sentinel流控，调用失败");
    }
​
}
​

配置消费者

这里我们结合着Sentinel控制台进行演示，所以我们需要先配置控制台的相关信息，在消费者的bootstrap.yaml 中如下配置

spring:
  application:
    name: user-openfeign-consumer
  cloud:
    nacos:
      discovery:
        server-addr: 192.168.199.128:8848 #Nacos地址
      config:
        server-addr: 192.168.199.128:8848 #Nacos地址
        file-extension: yaml #这里我们获取的yaml格式的配置
    #sentinel控制台
    sentinel:
      transport:
        #配置 Sentinel dashboard 地址
        dashboard: 192.168.199.128:8858
        #默认8719端口，假如被占用会自动从8719开始依次+1扫描,直至找到未被占用的端口
        port: 8719
​
#开启sentinel的支持
feign:
  sentinel:
    enabled: true

我们还需要在主启动类上添加注解，开启对OpenFeign的支持

package cuit.epoch.pymjl;
​
import cuit.epoch.pymjl.config.OpenFeignConfig;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;
​
/**
 * @author Pymjl
 * @version 1.0
 * @date 2022/8/31 23:37
 **/
@SpringBootApplication
@EnableFeignClients(defaultConfiguration = OpenFeignConfig.class)
public class OpenFeignApplication {
    public static void main(String[] args) {
        SpringApplication.run(OpenFeignApplication.class, args);
    }
}
​

/**
 * 在启动类的注解@EnableFeignClients上指定
 * 局部生效就在@FeignClient中指定,不能加@Configuration注解
 *
 * @author Pymjl
 * @version 1.0
 * @date 2022/9/1 13:17
 **/
public class OpenFeignConfig {
    @Bean
    public Logger.Level feignLogLevel() {
        // 日志级别为BASIC
        return Logger.Level.FULL;
    }
}

service接口

package cuit.epoch.pymjl.service;
​
import cuit.epoch.pymjl.entity.User;
import cuit.epoch.pymjl.feign.FeignServiceFallback;
import cuit.epoch.pymjl.result.CommonResult;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
​
/**
 * @author Pymjl
 * @version 1.0
 * @date 2022/9/1 0:03
 **/
@FeignClient(value = "user-service", fallback = FeignServiceFallback.class)
public interface UserFeignClient {
    /**
     * 注册
     *
     * @return {@code CommonResult<String>}
     */
    @GetMapping("/user/register")
    CommonResult<String> register();
​
    /**
     * 得到
     *
     * @param id id
     * @return {@code CommonResult<User>}
     */
    @GetMapping("/user/get/{id}")
    CommonResult<User> get(@PathVariable("id") Long id);
}

编写降级异常处理类

package cuit.epoch.pymjl.feign;
​
import cuit.epoch.pymjl.constant.ResultEnum;
import cuit.epoch.pymjl.entity.User;
import cuit.epoch.pymjl.result.CommonResult;
import cuit.epoch.pymjl.result.ResultUtils;
import cuit.epoch.pymjl.service.UserFeignClient;
import org.springframework.stereotype.Component;
​
/**
 * @author Pymjl
 * @version 1.0
 * @date 2022/9/17 22:06
 **/
@Component
public class FeignServiceFallback implements UserFeignClient {
    @Override
    public CommonResult<String> register() {
        return ResultUtils.fail(ResultEnum.SENTINEL_FALLBACK_ERROR);
    }
​
    @Override
    public CommonResult<User> get(Long id) {
        return ResultUtils.fail(ResultEnum.SENTINEL_FALLBACK_ERROR);
    }
}
​

测试

接下来，启动项目，进行测试。我们先调用消费者的接口，然后可以在控制台中Sentinel看到

然后我们添加如图所示的降级规则：

随后我们对接口进行测试访问：

如图所示，当请求次数为偶数时就会抛出异常，然后服务进行降级，生产者代码逻辑如下：

    private static final AtomicInteger ATOMIC_INTEGER = new AtomicInteger(0);

    @GetMapping("/get/{id}")
    @SentinelResource(value = "getUser")
    public CommonResult<User> get(@PathVariable("id") Long id) {
        int cnt = ATOMIC_INTEGER.incrementAndGet();
        log.info("cnt=={}", cnt);
        if (cnt % 2 == 0) {
            throw new AppException("发生了异常");
        }
        return ResultUtils.success(userService.get(id));
    }

当请求次数为奇数时就可以正常访问

然后当我们快速连续的访问多次该接口以后，服务会根据我们配置的降级规则，Sentinel会对服务进行熔断，熔断后无论请求次数为奇数还是偶数，请求都会被拒绝，只有等熔断时长过了后才有可能恢复服务

小结

总之，因为Spring Cloud Alibab已经集成了Sentinel，所以我们使用Spring Cloud来集成Sentinel非常方便，总结下来就这几个步骤：

1. 引入对应的依赖
2. 开启Sentinel支持
3. 编写FeignClient，并为FeignClient指定对应的降级处理类
4. 编写对应的降级异常处理类，该类需要实现FeignClient