前言

之前已经讲过断路器组件的相关作用及集成方案，具体参见文章Spring Cloud进阶之路 | 六：断路器（hystrix）。

那么，作为所有微服务的前置网关服务，承载了路由、身份认证、鉴权、审计、日志收集、统计、流控等重要功能，必须要保证高可靠性和稳定性。同时，为了实现上述的重要功能，也势必会通过远程调用的方式（rest、feign）依赖调用其它服务。

如此一来，就必须要集成断路器，以免依赖服务不可用造成网关服务停摆，进而造成整个服务大面积瘫痪。

准备工作

zuul已经集成了ribbon，所以，集成断路器也很简单。复用上篇文章Spring Cloud进阶之路 | 十四：服务网关重构（FactoryBean、动态配置、token解析、user传递）的全部工程：xmall-auth、xmall-product、xmall-zuul。

改造zuul

依赖改造

添加spring-cloud-starter-openfeign、spring-cloud-starter-netflix-hystrix依赖，修改后的pom文件如下。

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>com.luas.cloud</groupId>
        <artifactId>java-boot-parent-2.1</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>../../java-boot-parent-2.1</relativePath>
    </parent>

    <groupId>com.luas.xmall</groupId>
    <artifactId>xmall-zuul</artifactId>
    <version>1.0.0-SNAPSHOT</version>

    <name>xmall-zuul</name>
    <description>网关服务</description>

    <properties>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-zuul</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-oauth2</artifactId>
        </dependency>

        <!-- nacos cloud -->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId>
        </dependency>

        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>


    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

启动类改造

启动类分别添加注解@EnableCircuitBreaker、@EnableFeignClients以开启hystrix、feign。

package com.luas.xmall.gateway;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;
import org.springframework.cloud.openfeign.EnableFeignClients;

@EnableFeignClients
@EnableCircuitBreaker
@EnableZuulProxy
@SpringBootApplication
public class XmallZuulApplication {

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

}

创建客户端

为方便记，不再创建其它工程，直接创建xmall-product服务的feign客户端，供zuul调用，以模拟断路器过程。

创建SkuService。

package com.luas.xmall.gateway.product.clients;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@FeignClient(name = "xmall-product", fallback = SkuFallbackService.class)
public interface SkuService {

    @RequestMapping(value = "/sku/{id}", method = RequestMethod.GET)
    Object info(@PathVariable("id") String skuId);

}

创建SkuFallbackService。

package com.luas.xmall.gateway.product.clients;

import cn.hutool.core.map.MapUtil;
import org.springframework.stereotype.Component;

@Component
public class SkuFallbackService implements SkuService {

    @Override
    public Object info(String skuId) {
        return MapUtil.builder()
                .put("skuId", "0000000")
                .put("name", "未知")
                .put("price", "99999")
                .put("port", "未知")
                .build();
    }

}

模拟调用

创建SkuFeignFilter，类型为前置过滤器，顺序在前置身份认证之后。因此，需要先申请授权，访问sku接口，然后该过滤器才能执行的到。

package com.luas.xmall.gateway.filter;

import com.luas.xmall.gateway.product.clients.SkuService;
import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.exception.ZuulException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.util.Random;

import static org.springframework.cloud.netflix.zuul.filters.support.FilterConstants.PRE_TYPE;

@Component
public class SkuFeignFilter extends ZuulFilter {

    private Logger logger = LoggerFactory.getLogger(getClass());

    @Autowired
    private SkuService skuService;

    @Override
    public String filterType() {
        return PRE_TYPE;
    }

    @Override
    public int filterOrder() {
        return 1;
    }

    @Override
    public boolean shouldFilter() {
        return true;
    }

    @Override
    public Object run() throws ZuulException {
        Object skuInfo = this.skuService.info("" + new Random().nextInt(4));

        this.logger.info("sku info is {}", skuInfo);

        return null;
    }
}

配置改造

添加feign hystrix开关配置。