分布式微服务应用的熔断和降级介绍与实现

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestUserController
{
    @GetMapping("/user/info")
    public Object info()
    {
        return "{\"username\":\"admin\",\"password\":\"admin123\"}";
    }
}

@SpringBootApplication
public class RuoYiXxxxApplication
{
    public static void main(String[] args)
    {
        SpringApplication.run(RuoYiXxxxApplication.class, args);
        System.out.println("(◠‿◠)ﾉﾞ Xxxx启动成功 ლ(´ڡ`ლ)ﾞ \n" +
                " .-------. ____ __ \n" +
                " | _ _ \\ \\ \\ / / \n" +
                " | ( ' ) | \\ _. / ' \n" +
                " |(_ o _) / _( )_ .' \n" +
                " | (_,_).' __ ___(_ o _)' \n" +
                " | |\\ \\ | || |(_,_)' \n" +
                " | | \\ `' /| `-' / \n" +
                " | | \\ / \\ / \n" +
                " ''-' `'-' `-..-' ");
    }
}

/** * 用户接口 * * @author ruoyi */
public interface IUserService
{
    public Object selectUserByName(String username);
}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;

/** * 用户实现 * * @author ruoyi */
@Service
public class IUserServiceImpl implements IUserService
{
    @Autowired
    private RestTemplate restTemplate;

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

    @SentinelResource(value = "selectUserByName", blockHandler = "selectUserByNameBlockHandler", fallback = "selectUserByNameFallback")
    @Override
    public Object selectUserByName(String username)
    {
        return restTemplate.getForObject("http://localhost:9201/user/info/" + username, String.class);
    }

    // 服务流量控制处理，参数最后多一个 BlockException，其余与原函数一致。
    public Object selectUserByNameBlockHandler(String username, BlockException ex)
    {
        System.out.println("selectUserByNameBlockHandler异常信息：" + ex.getMessage());
        return "{\"code\":\"500\",\"msg\": \"" + username + "服务流量控制处理\"}";
    }

    // 服务熔断降级处理，函数签名与原函数一致或加一个 Throwable 类型的参数
    public Object selectUserByNameFallback(String username, Throwable throwable)
    {
        System.out.println("selectUserByNameFallback异常信息：" + throwable.getMessage());
        return "{\"code\":\"500\",\"msg\": \"" + username + "服务熔断降级处理\"}";
    }

}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestUserController
{
    @Autowired
    private IUserService userService;

    @GetMapping("/info/{username}")
    public Object info(@PathVariable("username") String username)
    {
        return userService.selectUserByName(username);
    }
}

private void initFlowQpsRule() {
    List<FlowRule> rules = new ArrayList<>();
    FlowRule rule = new FlowRule(resourceName);
    // set limit qps to 20
    rule.setCount(20);
    rule.setGrade(RuleConstant.FLOW_GRADE_QPS);
    rule.setLimitApp("default");
    rules.add(rule);
    FlowRuleManager.loadRules(rules);
}

private void initDegradeRule() {
    List<DegradeRule> rules = new ArrayList<>();
    DegradeRule rule = new DegradeRule();
    rule.setResource(KEY);
    // set threshold RT, 10 ms
    rule.setCount(10);
    rule.setGrade(RuleConstant.DEGRADE_GRADE_RT);
    rule.setTimeWindow(10);
    rules.add(rule);
    DegradeRuleManager.loadRules(rules);
}

@Bean
@SentinelRestTemplate(blockHandler = "handleException", blockHandlerClass = ExceptionUtil.class, fallback = "fallback", fallbackClass = ExceptionUtil.class)
public RestTemplate restTemplate() {
	return new RestTemplate();
}

import com.alibaba.cloud.sentinel.rest.SentinelClientHttpResponse;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import org.springframework.http.HttpRequest;
import org.springframework.http.client.ClientHttpRequestExecution;
import org.springframework.http.client.ClientHttpResponse;

public class ExceptionUtil
{
    // 服务流量控制处理
    public static ClientHttpResponse handleException(HttpRequest request, byte[] body,
            ClientHttpRequestExecution execution, BlockException exception)
    {
        exception.printStackTrace();
        return new SentinelClientHttpResponse("{\"code\":\"500\",\"msg\": \"服务流量控制处理\"}");
    }

    // 服务熔断降级处理
    public static ClientHttpResponse fallback(HttpRequest request, byte[] body, ClientHttpRequestExecution execution,
            BlockException exception)
    {
        exception.printStackTrace();
        return new SentinelClientHttpResponse("{\"code\":\"500\",\"msg\": \"服务熔断降级处理\"}");
    }
}

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

/** * 用户服务 * * @author ruoyi */
@FeignClient(contextId = "remoteUserService", value = "ruoyi-system", fallbackFactory = RemoteUserFallbackFactory.class)
public interface RemoteUserService
{
    /** * 通过用户名查询用户信息 * * @param username 用户名 * @return 结果 */
    @GetMapping(value = "/user/info/{username}")
    public Object getUserInfo(@PathVariable("username") String username);
}

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import feign.hystrix.FallbackFactory;

/** * 用户服务降级处理 * * @author ruoyi */
@Component
public class RemoteUserFallbackFactory implements FallbackFactory<RemoteUserService>
{
    private static final Logger log = LoggerFactory.getLogger(RemoteUserFallbackFactory.class);

    @Override
    public RemoteUserService create(Throwable throwable)
    {
        log.error("用户服务调用失败:{}", throwable.getMessage());
        return new RemoteUserService()
        {
            @Override
            public Object getUserInfo(String username)
            {
                return "{\"code\":\"500\",\"msg\": \"用户服务熔断降级处理\"}";
            }
        };
    }
}

@EnableFeignClients(basePackages = "com.ruoyi")