流控

简介

流控规则是用于完成服务流控的。服务流控即对访问流量的控制，也称为服务限流。

Sentinel实现流控的原理是监控应用流量的QS或并发线程数等指标，当达到指定的阈值时对再到来的请求进行进行控制，以避免被瞬时的流量高峰冲垮，从而保障应用的高可用性。

在流控规则上设置单机阈值为2，表示并并发出超过2的时候，则开启流控

当方法注解标注了 blockHandler ，如果没有在入参上BlockException，那么也不会进入方法

@RequestMapping("/sen")
@RestController
public class ProviderController {

    @GetMapping
    @SentinelResource(blockHandler = "blockErrorMSg")
    public String list() {
        return "sentinel list ";
    }

    public String blockErrorMSg(BlockException blockException) {
        return "blockErrorMSg" + blockException.getMessage();
    }

}

API 方法

设置 setResource ,在那个方法上 标注@SentinelResource 中，要指定 value 不然无效

1. 启动类

@SpringBootApplication
public class Sentinel10000Application {

    public static void main(String[] args) {
        SpringApplication.run(Sentinel10000Application.class, args);
        initFlowRule();
    }

    public static void initFlowRule() {
        List<FlowRule> rules = new ArrayList<>();
        rules.add(getConfig());
        FlowRuleManager.loadRules(rules);
    }

    public static FlowRule getConfig() {
        FlowRule flowRule = new FlowRule();
        //哪个方法
        flowRule.setResource("list");
        //指定规则类型
        flowRule.setGrade(RuleConstant.FLOW_GRADE_QPS);
        //指定 QPS
        flowRule.setCount(3);
        //来源
        flowRule.setLimitApp("default");
        return flowRule;
    }

}

2. 流控的方法

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.gao.sentinel.entity.Depart;
import com.gao.sentinel.feign.DepartFeignService;
import jakarta.annotation.security.DenyAll;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.AutoConfigureOrder;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RequestMapping("/sen")
@RestController
public class ProviderController {

    @GetMapping
    @SentinelResource(value = "list", blockHandler = "blockErrorMSg")
    public String list() {
        return "sentinel list ";
    }

    public String blockErrorMSg(BlockException blockException) {
        return "blockErrorMSg" + blockException.getMessage();
    }

}

使用资源实体方式

好处就是当自己使用了规则之外，还想使用别人的规则，就可以使用资源实体方式

import com.alibaba.csp.sentinel.Entry;
import com.alibaba.csp.sentinel.SphU;
import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.gao.sentinel.entity.Depart;
import com.gao.sentinel.feign.DepartFeignService;
import jakarta.annotation.security.DenyAll;
import org.springframework.boot.autoconfigure.AutoConfigureOrder;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RequestMapping("/sen")
@RestController
public class ProviderController {

    @GetMapping
    public String list() {
        Entry list = null;
        try {
            list = SphU.entry("list");
            return "sentinel list ";
        } catch (BlockException e) {
            return "entry error";
        } finally {
            if (list != null) {
                list.exit();
            }
        }

    }


}