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

框架	版本
Spring Boot	2.0.0.RELEASE
Spring Cloud	Finchley.RELEASE
Zuul	1.3.1
JDK	1.8.x

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

项	说明
getRoute()	该Provider应用的Route ID，例如：testservice，如果设置为 * ，那就对所有路由生效
fallbackResponse(String route, Throwable cause)	快速回退失败/响应，即处理异常并返回对应输出/响应内容。route：发生异常的RouteID，cause：触发快速回退/失败的异常/错误
ClientHttpResponse	Spring提供的HttpResponse接口。可以通过实现该接口自定义Http status、body、header

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