【Fegin技术专题】「原生态」打开Fegin之RPC技术的开端，你会使用原生态的Fegin吗？(下)

内容简介

在项目开发中，除了考虑正常的调用之外，负载均衡和故障转移也是关注的重点，这也是feign + ribbon的优势所在，基于上面两篇文章的基础，接下来我们开展最后一篇原生态fegin结合ribbon服务进行服务远程调用且实现负载均衡机制，也帮助大家学习ribbon奠定基础。

maven依赖

<dependencies><dependency><groupId>com.netflix.feigngroupId><artifactId>feign-coreartifactId><version>8.18.0version>dependency><dependency><groupId>com.netflix.feigngroupId><artifactId>feign-jacksonartifactId><version>8.18.0version>dependency><dependency><groupId>com.netflix.feigngroupId><artifactId>feign-ribbonartifactId><version>8.18.0version>dependency><dependency><groupId>com.netflix.archaiusgroupId><artifactId>archaius-coreartifactId>
dependency>dependencies>
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其中feign-core和feign-ribbon是必须的，如果需要在服务消费端和服务生产端之间进行对象交互，建议使用feign-jackson

配置读取

import com.netflix.config.ConfigurationManager;
import feign.Feign;
import feign.jackson.JacksonDecoder;
import feign.jackson.JacksonEncoder;
import feign.ribbon.RibbonClient;
public class AppRun {public static void main(String[] args) throws Exception {User param = new User();param.setUsername("test");RemoteService service = Feign.builder().client(RibbonClient.create()).encoder(new JacksonEncoder()).decoder(new JacksonDecoder()).options(new Options(1000, 3500)).retryer(new Retryer.Default(5000, 5000, 3)).target(RemoteService.class, "http://remote-client/gradle-web");for (int i = 1; i 10; i++) {User result = service.getOwner(param);System.out.println(result.getId() + "," + result.getUsername());}}
}
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声明了一个User类型的对象param，该对象将作为参数被发送至服务生产端。
重点在于通过RibbonClient.create()使得Feign对象获得了Ribbon的特性。之后通过encoder,decoder设置编码器与解码器，并通过target方法将之前定义的接口RemoteService与一个URL地址http://remote-client/gradle-web进行了绑定。

现在来看remote-client.properties中的配置项，主要多是RemoteClient的配置机制

remote-client.ribbon.MaxAutoRetries=1
remote-client.ribbon.MaxAutoRetriesNextServer=1
remote-client.ribbon.OkToRetryOnAllOperations=true
remote-client.ribbon.ServerListRefreshInterval=2000
remote-client.ribbon.ConnectTimeout=3000
remote-client.ribbon.ReadTimeout=3000
remote-client.ribbon.listOfServers=127.0.0.1:8080,127.0.0.1:8085
remote-client.ribbon.EnablePrimeConnections=false
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所有的key都以remote-client开头，表明这些配置项作用于名为remote-client的服务。其实就是与之前绑定RemoteService接口的URL地址的schema相对应。

重点看remote-client.ribbon.listOfServers配置项，该配置项指定了服务生产端的真实地址。

在调用时会被替换为：

@RequestLine指定的地址进行拼接，得到最终请求地址。本例中最终请求地址为：

由于使用的ribbon，所以feign不再需要配置超时时长，重试策略。ribbon提供了更为完善的策略实现。

本例中，服务生产端是一个简单的springMvc，实现如下:


public class UserController {public User list( User user) throws InterruptedException{HttpServletRequest request = ((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getRequest();user.setId(new Long(request.getLocalPort()));user.setUsername(user.getUsername().toUpperCase());return user;}
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故障转移是通过remote-client.properties中的配置项进行配置。

首先利用archaius项目的com.netflix.config.ConfigurationManager读取配置文件remote-client.properties,该文件位于src/main/resources下。

负载均衡的策略又是如何设置呢？

import com.netflix.client.ClientFactory;
import com.netflix.client.config.IClientConfig;
import com.netflix.config.ConfigurationManager;
import com.netflix.loadbalancer.ILoadBalancer;
import com.netflix.loadbalancer.RandomRule;
import com.netflix.loadbalancer.ZoneAwareLoadBalancer;
import feign.Feign;
import feign.jackson.JacksonDecoder;
import feign.jackson.JacksonEncoder;
import feign.ribbon.LBClient;
import feign.ribbon.LBClientFactory;
import feign.ribbon.RibbonClient;
public class AppRun {public static void main(String[] args) throws Exception {ConfigurationManager.loadPropertiesFromResources("remote-client.properties");User param = new User();param.setUsername("test");RibbonClient client = RibbonClient.builder().lbClientFactory(new LBClientFactory() {public LBClient create(String clientName) {IClientConfig config = ClientFactory.getNamedConfig(clientName);ILoadBalancer lb = ClientFactory.getNamedLoadBalancer(clientName);ZoneAwareLoadBalancer zb = (ZoneAwareLoadBalancer) lb;zb.setRule(new RandomRule());return LBClient.create(lb, config);}}).build();RemoteService service = Feign.builder().client(client).encoder(new JacksonEncoder()).decoder(new JacksonDecoder()).options(new Options(1000, 3500)).retryer(new Retryer.Default(5000, 5000, 3)).target(RemoteService.class, "http://remote-client/gradle-web");for (int i = 1; i 10; i++) {User result = service.getOwner(param);System.out.println(result.getId() + "," + result.getUsername());}}
}
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private IRule zoneAvoidanceRule() {return new ZoneAvoidanceRule();}private IRule randomRule() {return new RandomRule();}
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不再使用RibbonClient.create()来创建默认的RibbonClient，而是通过RibbonClient.builder()获得feign.ribbon.Builder,进而设置LBClientFactory的实现来定制LBClient，在创建LBClient的过程中即可指定负载策略的具体实现。