springcloud之openfeign集成sentinel限流

1.先调用服务接口，才会在sentinel显示应用名称

2.sentinel 限流默认1秒内多少访问量

3.sentinel规则持久化，服务重启以后不用在配置

4.使用nacos进行sentinel规则持久化


1.配置
spring:
  application:
    name: nacos-loadbalancer-service
  cloud:
    nacos:
      discovery:
        server-addr: 49.234.12.67:8848
    loadbalancer:
      cache: # 负载均衡缓存配置
        enabled: true # 开启缓存
        ttl: 5s # 设置缓存时间
        capacity: 256 # 设置缓存大小
      retry: # 重试配置
        enabled: true
        max-retries-on-same-service-instance: 1
        max-retries-on-next-service-instance: 1
      zone: test
    sentinel:
      transport:
        dashboard: 49.234.12.67:8180
service-url:
  nacos-user-service: http://nacos-user-service
feign:
  sentinel:
    enabled: true
  client:
    config:
      default: # Feign调用超时配置
        connectTimeout: 5000
        readTimeout: 5000

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

3.其它限流知识
a.Blocked by Sentinel (flow limiting)
sentinel自定义返回值处理
import com.alibaba.csp.sentinel.adapter.spring.webmvc.callback.BlockExceptionHandler;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.alibaba.csp.sentinel.slots.block.authority.AuthorityException;
import com.alibaba.csp.sentinel.slots.block.degrade.DegradeException;
import com.alibaba.csp.sentinel.slots.block.flow.FlowException;
import com.alibaba.csp.sentinel.slots.block.flow.param.ParamFlowException;
import com.alibaba.csp.sentinel.slots.system.SystemBlockException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.stereotype.Component;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
public class SentinelExceptionHandler implements BlockExceptionHandler {
    @Override
    public void handle(HttpServletRequest request, HttpServletResponse response, BlockException ex) throws Exception {
            String msg = null;
            if (ex instanceof FlowException) {
                msg = "限流了";
            } else if (ex instanceof DegradeException) {
                msg = "降级了";
            } else if (ex instanceof ParamFlowException) {
                msg = "热点参数限流";
            } else if (ex instanceof SystemBlockException) {
                msg = "系统规则限流或降级";
            } else if (ex instanceof AuthorityException) {
                msg = "授权规则不通过";
            }
            // http状态码
            response.setStatus(500);
            response.setCharacterEncoding("utf-8");
            response.setHeader("Content-Type", "application/json;charset=utf-8");
            response.setContentType("application/json;charset=utf-8");
            // spring mvc自带的json操作工具，叫jackson
            String path = request.getServletPath();
            if (path != null) {
                msg = String.format("接口[%s]%s", path, msg);
            }
            new ObjectMapper().writeValue(response.getWriter(), msg);
        }
}


b.@FeignClient(value = "nacos-user-service", fallbackFactory = UserServiceFallbackFactory.class)
@Component
public class UserServiceFallbackFactory implements FallbackFactory<UserService> {