直接使用hystrix时:
服务消费方:

@RestController
@RequestMapping("/consumer/users")
public class UserController
{
    @Autowired
    private RestTemplate restTemplate;

    @Autowired
    private DiscoveryClient discoveryClient;

    @GetMapping("{id}")
    // 当此方法无法正常返回的时候 调用降级方法
    @HystrixCommand(fallbackMethod = "getUserByIdFallBack")
    public User getUserById(@PathVariable("id") Long id)
    {
        String url = "http://localhost:8081/users/" + id;
        return restTemplate.getForObject(url, User.class);
    }
    public User getUserByIdFallBack(Long id)
    {
        User user = new User();
        user.setId(-1L);
        user.setName("出现错误");
        return user;
    }
}

yml配置:

hystrix:
  command:
    default:
      execution:
        isolation:
          thread:
            timeoutInMilliseconds: 3000 # 设置hystrix的超时时间为3000ms, 之后才调用降级方法

服务提供方:

@RestController
@RequestMapping("/users")
public class UserController
{
    @Autowired
    private IUserService userService;

    @GetMapping("{id}")
    public User getUserById(@PathVariable("id") Long id)
    {
        try
        {
            Thread.sleep(12500); // 远大于三秒
        }
        catch (InterruptedException e)
        {
            e.printStackTrace();
        }
        System.out.println("sb");
        return userService.getUserById(id);
    }
}

此时访问http://localhost/consumer/users/1时, 会因为服务提供方超时而进入降级方法, 并且超时时间恰好是3s

但是如果过通过feign进行调用, hystrix超时时间的配置就会失效
默认情况下: 使用feign进行远程调用, 如果provider中的方法在1s内没有返回, 则会超时报错
如果想延长这个时间就应该设置feign的超时时间
超过feign的超时时间但是没有超过hystrix的超时时间, 还是会进入降级方法
使用feign
服务消费方:

@FeignClient(value = "service-provider", fallback = UserClientFallback.class)
public interface UserClient
{
    @GetMapping("/users/{id}")
    User getUserById(@PathVariable("id") Long id);
}

// 此类用来编写降级方法
@Component
public class UserClientFallback implements UserClient
{
    @Override
    public User getUserById(Long id)
    {
        User user = new User();
        user.setName("UserClientFallback中的降级方法");
        return user;
    }
}

@RestController
@RequestMapping("/consumer/feign/users")
public class UserFeignController
{
    @Autowired
    private UserClient userClient;

    @GetMapping("{id}")
    public User getUserById(@PathVariable("id") Long id)
    {
        return userClient.getUserById(id);
    }
}

yml

feign:
  hystrix:
    enabled: true
  client:
    config:
      default:
        connectTimeout: 2000 # feign 的超时设置
        readTimeout: 2000

此时访问http://localhost/consumer/feign/users/1时, 会因为服务提供方超时而进入降级方法, 并且超时时间恰好是2s