SpringCloud(Finchley版)2 - Ribbon+Hystrix

一, 簡介

    Ribbon 是一個負載均衡客戶端, 能夠很好的控制HTTP和TCP的一些行爲;

    在微服務架構中, Ribbon 組件負責 每一個獨立服務 之間的 相互通訊調用;

    Hystrix 斷路由處理; 

    若是單個服務出現問題, 調用這個服務就會出現線程阻塞, 此時如有大量的請求涌入, Servlet容器的線程資源會被消耗完畢, 致使服務癱瘓.

    服務與服務之間的依賴性, 故障會傳播, 會對整個微服務系統形成災難性的嚴重後果, 這就是服務故障的「雪崩」效應. 

    斷路打開後，可用避免連鎖故障，fallback方法能夠直接返回一個固定值。

二, 準備工作

    1, 啓動註冊中心;   2, 啓動服務B;

三, 建立 cloud-c 服務,實現服務調用功能

    1, cloud-c pom.xml

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.gy.cloud</groupId>
        <artifactId>cloud</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <artifactId>cloud-c</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>cloud-c</name>


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

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
  
        <!-- netflix-ribbon 該包能夠不用引用, 其實 eureka-client 已經自動引入了該包 -->
        <!-- 
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>
        -->
        <!-- 熔斷, 服務調用失敗後的保護組件 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>
    </dependencies>

</project>

    2, cloud-c application.yml

server:
  port: 8763

spring:
  application:
    name: service-c

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

    3, cloud-c CloudCApplication 啓動類 : 

package com.gy.cloud.cloudc;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@EnableHystrix
@EnableEurekaClient
@SpringBootApplication
public class CloudCApplication {

    public static void main(String[] args) {
        SpringApplication.run(CloudCApplication.class, args);
        System.out.println("=== 消費服務C啓動成功 ===");
    }

    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

    4,  cloud-c  Controller 接口 :

package com.gy.cloud.cloudc;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HiController {

    @Autowired
    private HiService hiService;

    @GetMapping("hi")
    public Object hi(String name) {
        name = name == null ? "SERVICE-C" : name;
        return hiService.hi(name);
    }


}

    5, 調用 SERVICE-B

package com.gy.cloud.cloudc;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

@Service
public class HiService {

    @Autowired
    private RestTemplate restTemplate;

    @HystrixCommand(fallbackMethod = "hiError")
    public String hi(String name) {
        System.out.println(name);
        String hi = restTemplate.getForObject("http://SERVICE-B/hi?name=" + name, String.class);
        System.out.println(hi);
        return hi;
    }
    // 熔斷: 當服務B調用失敗, 執行此方法
    public String hiError(String name) {
        return "Hi, " + name +", Sorry Error !";
    }

}

    6,  啓動 SERVICE-C , 訪問 :   http://localhost:8763/hi

    7,  斷開 SERVICE-B , 訪問 :   http://localhost:8763/hi

學習文檔

方誌朋的博客 :  https://www.fangzhipeng.com/springcloud/2018/08/30/sc-f2-ribbon/

項目源碼:  https://gitee.com/ge.yang/spring-demo/tree/master/cloud