spring cloud zuul 与 sentinel 结合使用

本来大型服务处理请求超时，限流，降级熔断工作用hystrix,但是这个这个项目不再更新了，虽说它现在提供的版本不会影响到大多数开发者的使用，但是长远考虑，被更换是一件必然的事，而且现在像resilience4j， Sentinel这样的替代品出现，今天我们就看看使用zuul 与 Sentinel整合，实现降级与超时处理，其实网上有很多这样的教程，这里我只是做一个自己的笔记而已

1.必须的依赖

        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-eureka-clientartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-zuulartifactId>
        dependency>

        <dependency>
            <groupId>com.alibaba.cspgroupId>
            <artifactId>sentinel-zuul-adapterartifactId>
            <version>1.7.1version>
        dependency>

2. 配置文件，其实Sentinel在这里没什么配置

   server:
     port: 6001
   spring:
     application:
       name: e-zuul
   
   eureka:
     instance:
       hostname: localhost
       lease-expiration-duration-in-seconds: 90 #表示服务端多长时间没有接受到心跳信息后可以删除自己
       lease-renewal-interval-in-seconds: 30 #表示需要要向服务端发送信息，表示自己还活着
       ip-address: true
     client:
       healthcheck:
         enabled: true #客户端心跳检测
       service-url:
         defaultZone: http://${eureka.instance.hostname}:3001/eureka/
   
   zuul:
     add-proxy-headers: true
     LogFilter:
       pre:
         disable=true:
     routes:
       e-email:
         serviceId: e-email
         path: /email/**
       e-user:
         serviceId: e-user
         path: /user/**
   

3. 配置类, 其实配置类和后边的降级回调处理类才是关键，而且配置类中几个关于zuul与Sentinel的过滤器非常关键，这里要是不提供它们，将无法实现我们想要的功能，还有就是网关规则，可以选择qps, 超时，线程等，setGrade(RuleConstant.DEGRADE_GRADE_RT)提供选择不同的策略

   package com.mjlf.ezuul.config;
   
   import com.alibaba.csp.sentinel.adapter.gateway.common.rule.GatewayFlowRule;
   import com.alibaba.csp.sentinel.adapter.gateway.common.rule.GatewayRuleManager;
   import com.alibaba.csp.sentinel.adapter.gateway.zuul.fallback.ZuulBlockFallbackManager;
   import com.alibaba.csp.sentinel.adapter.gateway.zuul.filters.SentinelZuulErrorFilter;
   import com.alibaba.csp.sentinel.adapter.gateway.zuul.filters.SentinelZuulPostFilter;
   import com.alibaba.csp.sentinel.adapter.gateway.zuul.filters.SentinelZuulPreFilter;
   import com.alibaba.csp.sentinel.slots.block.RuleConstant;
   import com.alibaba.csp.sentinel.slots.block.degrade.DegradeRule;
   import com.alibaba.csp.sentinel.slots.block.degrade.DegradeRuleManager;
   import com.netflix.zuul.ZuulFilter;
   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.Configuration;
   
   import javax.annotation.PostConstruct;
   import java.util.HashSet;
   import java.util.Set;
   
   @Configuration
   public class ZuulConfig {
   
       @Bean
       public ZuulFilter sentinelZuulPreFilter() {
           // We can also provider the filter order in the constructor.
           return new SentinelZuulPreFilter();
       }
   
       @Bean
       public ZuulFilter sentinelZuulPostFilter() {
           return new SentinelZuulPostFilter();
       }
   
       @Bean
       public ZuulFilter sentinelZuulErrorFilter() {
           return new SentinelZuulErrorFilter();
       }
   
   
       @PostConstruct
       public void doInit() {
           // 注册 FallbackProvider
           ZuulBlockFallbackManager.registerProvider(new MyBlockFallbackProvider());
           initGatewayRules();
       }
   
       /**
        * 配置限流规则
        */
       private void initGatewayRules() {
           Set<GatewayFlowRule> rules = new HashSet<>();
           rules.add(new GatewayFlowRule("e-user").setCount(3) // 限流阈值
                   .setIntervalSec(1) // 统计时间窗口，单位是秒，默认是 1 秒
           );
           rules.add(new GatewayFlowRule("e-user")
                   .setGrade(RuleConstant.DEGRADE_GRADE_RT)//设置超时类型规则
                   .setMaxQueueingTimeoutMs(500)
           );
           GatewayRuleManager.loadRules(rules);
       }
   }
   

4. 回调处理类，当有请求被拦截到后，就会调用降级回调方法

// 自定义 FallbackProvider
@Component
public class MyBlockFallbackProvider implements ZuulBlockFallbackProvider {

    private Logger logger = LoggerFactory.getLogger(DefaultBlockFallbackProvider.class);

    // you can define route as service level 
    @Override
    public String getRoute() {
        return "*";
    }

    @Override
    public BlockResponse fallbackResponse(String route, Throwable cause) {
        RecordLog.info(String.format("[Sentinel DefaultBlockFallbackProvider] Run fallback route: %s", route));
        if (cause instanceof BlockException) {
            return new BlockResponse(429, "Sentinel block exception", route);
        } else {
            return new BlockResponse(500, "System Error", route);
        }
    }
}