Spring Cloud 入门教程8、服务网关Zuul+Hystrix：断路处理与监控

一、前言

1、本篇主要内容

• 通过实现FallbackProvider进行Zuul网关路由断路处理
• Zuul+Hystrix路由断路监控配置与说明

2、本篇环境信息

3、准备工作

参考上一篇：https://ken.io/note/spring-cloud-zuul-quickstart
基于源码：https://github.com/ken-io/springcloud-course/tree/master/chapter-07

• 准备Eureka Server、服务提供者

启动Eureka Server： http://localhost:8800
启动Test Service：http://localhost:8602，http://localhost:8603

二、服务网关Zuul：服务断路处理

Zuul作为服务网关为了保证自己不被服务拖垮，本身已经集成了Hystrix对路由转发进行隔离。
为了方便开发人员对服务短路进行自定义处理，
Zuul 提供了 ZuulFallbackProvider 接口，开发人员可以通过实现该接口来完成自定义Hystrix Fallback

Spring Cloud Zuul 提供了 FallbackProvider替代了ZuulFallbackProvider接口。因此我们实现FallbackProvider即可

基于上一篇中zuul项目的源码进行修改即可：https://github.com/ken-io/springcloud-course/tree/master/chapter-07/zuul

1、实现FallbackProvider

在src\main\java\io\ken\springcloud\zuul创建package：provider
然后创建Filter类：ApiFallbackProvider.java

实现FallbackProvider并标记为@Component

package io.ken.springcloud.zuul.provider;

import com.netflix.hystrix.exception.HystrixTimeoutException;
import org.springframework.cloud.netflix.zuul.filters.route.FallbackProvider;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.stereotype.Component;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.logging.Logger;

@Component
public class ApiFallbackProvider implements FallbackProvider {

    private Logger logger = Logger.getLogger(ApiFallbackProvider.class.toString());

    @Override
    public String getRoute() {
        return "*";
    }

    @Override
    public ClientHttpResponse fallbackResponse(String route, Throwable cause) {
        logger.warning(String.format("route:%s,exceptionType:%s,stackTrace:%s", route, cause.getClass().getName(), cause.getStackTrace()));
        String message = "";
        if (cause instanceof HystrixTimeoutException) {
            message = "Timeout";
        } else {
            message = "Service exception";
        }
        return fallbackResponse(message);
    }

    public ClientHttpResponse fallbackResponse(String message) {

        return new ClientHttpResponse() {
            @Override
            public HttpStatus getStatusCode() throws IOException {
                return HttpStatus.OK;
            }

            @Override
            public int getRawStatusCode() throws IOException {
                return 200;
            }

            @Override
            public String getStatusText() throws IOException {
                return "OK";
            }

            @Override
            public void close() {

            }

            @Override
            public InputStream getBody() throws IOException {
                String bodyText = String.format("{\"code\": 999,\"message\": \"Service unavailable:%s\"}", message);
                return new ByteArrayInputStream(bodyText.getBytes());
            }

            @Override
            public HttpHeaders getHeaders() {
                HttpHeaders headers = new HttpHeaders();
                headers.setContentType(MediaType.APPLICATION_JSON);
                return headers;
            }
        };

    }

}

• FallbackProvider 成员说明

2、回退/失败响应测试

启动zuul项目，访问 http://localhost:8888/testservice?token=123
会得到正常响应内容：

{
  "code": 0,
  "message": "hello",
  "content": null,
  "serviceName": "testservice",
  "host": "localhost:8602"
}

关掉testservice启动的实例。然后再访问 http://localhost:8888/testservice?token=123 ，就会看到

{
  "code": 999,
  "message": "Service unavailable:Timeout"
}

三、服务网关Zuul：服务断路监控/仪表盘

上一节咱们提到了，Zuul本身就集成了Hystrix，实际上Zuul的路由转发也是用到了Ribbon+Hystrix，也就意味着我们可以通过Hystrix Dashboard监控Zuul的工作情况

1、开启访问Hystri.stream入口

新建package：configuration，然后在此package下创建HystrixConfiguration.java

package io.ken.springcloud.zuul.configuration;

import com.netflix.hystrix.contrib.metrics.eventstream.HystrixMetricsStreamServlet;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class HystrixConfiguration {

    @Bean(name = "hystrixRegistrationBean")
    public ServletRegistrationBean servletRegistrationBean() {
        ServletRegistrationBean registration = new ServletRegistrationBean(
                new HystrixMetricsStreamServlet(), "/hystrix.stream");
        registration.setName("hystrixServlet");
        registration.setLoadOnStartup(1);
        return registration;
    }

    @Bean(name = "hystrixForTurbineRegistrationBean")
    public ServletRegistrationBean servletTurbineRegistrationBean() {
        ServletRegistrationBean registration = new ServletRegistrationBean(
                new HystrixMetricsStreamServlet(), "/actuator/hystrix.stream");
        registration.setName("hystrixForTurbineServlet");
        registration.setLoadOnStartup(1);
        return registration;
    }
}

配置完成后重启启动zuul，访问 http://localhost:8888/hystrix.stream 或者
http://localhost:8888/actuator/hystrix.stream
就可以看到Hystrix流信息.(之所以配置两个入口，是为了满足turbine需要)

//截取片段
{"type":"HystrixCommand","name":"testservice","group":"RibbonCommand","currentTime":1532412948030,"isCircuitBreakerOpen":false,"errorPercentage":100,"errorCount":1,"requestCount":1}

这时候我们通过已有看板以链接方式查看Hystrix Dashboard，或者可以用Turbine来聚合Hystrix数据了。
当然，也可以在zuul项目中引入Hystrix Dashboard 进行监控。

2、引入Hystrix Dashboard

• 修改pom.xml引入Hystrix Dashboard相关依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

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

• 修改App.java，加入 @EnableHystrixDashboard 注解

package io.ken.springcloud.zuul;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;

@EnableHystrixDashboard
@EnableZuulProxy
@EnableEurekaClient
@SpringBootApplication
public class App {
    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }
}

配置完成后重启启动zuul，访问 http://localhost:8888/hystrix ，就可以看到门户页

具体操作，不再赘述，参考本系列前面几篇Hystrix随笔即可

备注

• 本篇代码示例

https://github.com/ken-io/springcloud-course/tree/master/chapter-08

• 本篇参考

http://cloud.spring.io/spring-cloud-static/spring-cloud-netflix/2.0.0.RELEASE/single/spring-cloud-netflix.html#hystrix-fallbacks-for-routes

• 相关阅读

https://ken.io/note/spring-cloud-hystrix-dashboard-quickstart
https://ken.io/note/spring-cloud-hystrix-dashboard-turbine-quickstart

• 系列名称：Spring Cloud 入门教程
• 上一篇：Spring Cloud 入门教程7、服务网关（Zuul）
• 下一篇：Spring Cloud 入门教程9、服务限流/API限流（Zuul+RateLimiter）