Spring Cloud 入門教程八、服務網關Zuul+Hystrix：斷路處理與監控

1、前言

一、本篇主要內容

• 經過實現FallbackProvider進行Zuul網關路由斷路處理
• Zuul+Hystrix路由斷路監控配置與說明

二、本篇環境信息

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

三、準備工做

參考上一篇：https://ken.io/note/spring-cloud-zuul-quickstart
基於源碼：https://github.com/ken-io/springcloud-course/tree/master/chapter-07

• 準備Eureka Server、服務提供者

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

2、服務網關Zuul：服務斷路處理

Zuul做爲服務網關爲了保證本身不被服務拖垮，自己已經集成了Hystrix對路由轉發進行隔離。
爲了方便開發人員對服務短路進行自定義處理，
Zuul 提供了 ZuulFallbackProvider 接口，開發人員能夠經過實現該接口來完成自定義Hystrix Fallback

Spring Cloud Zuul 提供了 FallbackProvider替代了ZuulFallbackProvider接口。所以咱們實現FallbackProvider便可

基於上一篇中zuul項目的源碼進行修改便可：https://github.com/ken-io/springcloud-course/tree/master/chapter-07/zuul

一、實現FallbackProvider

在src\main\java\io\ken\springcloud\zuul建立package：provider
而後建立Filter類：ApiFallbackProvider.java

實現FallbackProvider並標記爲@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 成員說明

項	說明
getRoute()	該Provider應用的Route ID，例如：testservice，若是設置爲 * ，那就對全部路由生效
fallbackResponse(String route, Throwable cause)	快速回退失敗/響應，即處理異常並返回對應輸出/響應內容。route：發生異常的RouteID，cause：觸發快速回退/失敗的異常/錯誤
ClientHttpResponse	Spring提供的HttpResponse接口。能夠經過實現該接口自定義Http status、body、header

二、回退/失敗響應測試

啓動zuul項目，訪問 http://localhost:8888/testservice?token=123
會獲得正常響應內容：

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

關掉testservice啓動的實例。而後再訪問 http://localhost:8888/testservice?token=123 ，就會看到

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

3、服務網關Zuul：服務斷路監控/儀表盤

上一節我們提到了，Zuul自己就集成了Hystrix，實際上Zuul的路由轉發也是用到了Ribbon+Hystrix，也就意味着咱們能夠經過Hystrix Dashboard監控Zuul的工做狀況

一、開啓訪問Hystri.stream入口

新建package：configuration，而後在此package下建立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;
    }
}

配置完成後重啓啓動zuul，訪問 http://localhost:8888/hystrix.stream 或者
http://localhost:8888/actuator/hystrix.stream
就能夠看到Hystrix流信息.(之因此配置兩個入口，是爲了知足turbine須要)

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

這時候咱們經過已有看板以連接方式查看Hystrix Dashboard，或者能夠用Turbine來聚合Hystrix數據了。
固然，也能夠在zuul項目中引入Hystrix Dashboard 進行監控。

二、引入Hystrix Dashboard

• 修改pom.xml引入Hystrix Dashboard相關依賴

<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 註解

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);
    }
}

配置完成後重啓啓動zuul，訪問 http://localhost:8888/hystrix ，就能夠看到門戶頁

具體操做，再也不贅述，參考本系列前面幾篇Hystrix隨筆便可