Ribbon的EurekaRibbonClientConfiguration源码分析

一 介绍

当同时引入Spring Cloud Ribbon和Spring Cloud Eurek依赖时，会触发Eureka中实现的对Ribbon的自动化配置。Ribbon的自动化配置将会发生变化。

二 EurekaRibbonClientConfiguration源码解读

@Configuration
public class EurekaRibbonClientConfiguration {

    private static final Log log = LogFactory.getLog(EurekaRibbonClientConfiguration.class);

    @Value("${ribbon.eureka.approximateZoneFromHostname:false}")
    private boolean approximateZoneFromHostname = false;

    @RibbonClientName
    private String serviceId = "client";

    @Autowired(required = false)
    private EurekaClientConfig clientConfig;

    @Autowired(required = false)
    private EurekaInstanceConfig eurekaConfig;

    @Autowired
    private PropertiesFactory propertiesFactory;

    public EurekaRibbonClientConfiguration() {
    }

    public EurekaRibbonClientConfiguration(EurekaClientConfig clientConfig,
            String serviceId, EurekaInstanceConfig eurekaConfig,
            boolean approximateZoneFromHostname) {
        this.clientConfig = clientConfig;
        this.serviceId = serviceId;
        this.eurekaConfig = eurekaConfig;
        this.approximateZoneFromHostname = approximateZoneFromHostname;
    }

    @Bean
    @ConditionalOnMissingBean
    public IPing ribbonPing(IClientConfig config) {
        if (this.propertiesFactory.isSet(IPing.class, serviceId)) {
            return this.propertiesFactory.get(IPing.class, config, serviceId);
        }
        //IPing的实现由NIWSDiscoveryPing来完成
        NIWSDiscoveryPing ping = new NIWSDiscoveryPing();
        ping.initWithNiwsConfig(config);
        return ping;
    }

    @Bean
    @ConditionalOnMissingBean
    public ServerList<?> ribbonServerList(IClientConfig config, Provider<EurekaClient> eurekaClientProvider) {
        if (this.propertiesFactory.isSet(ServerList.class, serviceId)) {
            return this.propertiesFactory.get(ServerList.class, config, serviceId);
        }
        //discoveryServerList的维护机制由DiscoveryEnabledNIWSServerList来完成
        DiscoveryEnabledNIWSServerList discoveryServerList = new DiscoveryEnabledNIWSServerList(
                config, eurekaClientProvider);
        //serverList的维护机制有DomainExtractingServerList来完成
        DomainExtractingServerList serverList = new DomainExtractingServerList(
                discoveryServerList, config, this.approximateZoneFromHostname);
        return serverList;
    }

    @Bean
    public ServerIntrospector serverIntrospector() {
        return new EurekaServerIntrospector();
    }

    ......
    }
}

三 Spring Cloud Ribbon和Spring Cloud Eureka结合后配置说明

1 配置更简单

不再需要通过类似hello-service.ribbon.listOfServers参数来指定具体的服务实例清单，因为Eureka将会为我们维护所有的实例清单。

2 Spring Cloud Ribbon默认实现了区域亲和策略。

只需要在服务实例的元数据中增加zone参数来指定自己所在的区域。

eureka.instance.metadataMap.zone=shanghai

3 通过配置ribbon.eureka.enabled=false将服务的维护实例回归到<client>.ribbon.listOfServers参数配置。