Sentinel 链路限流

https://github.com/alibaba/Sentinel/wiki/%E6%B5%81%E9%87%8F%E6%8E%A7%E5%88%B6

NodeSelectorSlot 中记录了资源之间的调用链路，这些资源通过调用关系，相互之间构成一棵调用树。这棵树的根节点是一个名字为 machine-root 的虚拟节点，调用链的入口都是这个虚节点的子节点。

一棵典型的调用树如下图所示：

     	          machine-root
                    /       \
                   /         \
             Entrance1     Entrance2
                /             \
               /               \
      DefaultNode(nodeA)   DefaultNode(nodeA)

上图中来自入口 Entrance1 和 Entrance2 的请求都调用到了资源 NodeA，Sentinel 允许只根据某个入口的统计信息对资源限流。比如我们可以设置 strategy 为 RuleConstant.STRATEGY_CHAIN，同时设置 refResource 为 Entrance1 来表示只有从入口 Entrance1 的调用才会记录到 NodeA 的限流统计当中，而不关心经 Entrance2 到来的调用。

调用链的入口（上下文）是通过 API 方法 ContextUtil.enter(contextName) 定义的，其中 contextName 即对应调用链路入口名称。详情可以参考 ContextUtil 文档。

web-context-unify: false #默认将调用链路收敛

 application.yml

server:
  port: 8052
  #应用名称  （sentinel 会将该名称当作服务名称）
spring:
  application:
    name: order-sentinel
  cloud:
    sentinel:
      transport:
        dashboard: 127.0.0.1:8858
      web-context-unify: false #默认将调用链路收敛

package com.wsm.order.service;

public interface OrderService {
    public String getUser();
}

package com.wsm.order.service.impl;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.wsm.order.service.OrderService;
import org.springframework.stereotype.Service;

@Service
public class OrderServiceImpl implements OrderService {

    @Override
    @SentinelResource(value = "getUser",blockHandler = "blockHandlerGetUser")
    public String getUser() {
        return "查询用户";
    }

    public String blockHandlerGetUser(BlockException e){
        return "流控用户";
    }

}

package com.wsm.order.controller;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.wsm.order.service.OrderService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.concurrent.TimeUnit;

@RestController
@RequestMapping("/order")
public class OrderController {

    @Autowired
    OrderService orderService;

    @RequestMapping("/add")
    public String add(){
        System.out.println("下单成功！");
        return "生成订单";
    }

    @RequestMapping("/get")
    public String get(){
        System.out.println("查询订单！");
        return "查询订单";
    }

    @RequestMapping("/test1")
    public String test1(){
        return orderService.getUser();
    }

    @RequestMapping("/test2")
    public String test2(){
        return orderService.getUser();
    }

    @RequestMapping("/flow")
//    @SentinelResource(value = "flow",blockHandler = "flowBlockHandler")
    public String flow(){
        System.out.println("========flow====");
        return "正常访问";
    }

    public String flowBlockHandler(BlockException e){
        return "流控了";
    }

    @RequestMapping("/flowThread")
//    @SentinelResource(value = "flowThread",blockHandler = "flowThreadBlockHandler")
    public String flowThread() throws InterruptedException {
        TimeUnit.SECONDS.sleep(5);
        System.out.println("========flowThread====");
        return "正常访问";
    }

    public String flowThreadBlockHandler(BlockException e){
        return "flowThread流控了";
    }




}