Ribbon自动化配置源码解读

在引入Spring Cloud Ribbon依赖后，就能够自动化构建下面这些接口的实现：

一 相关接口 

• IClientConfig：Ribbon的客户端配置，默认采用DefaultClientConfigImpl实现。
• IRule：默认采用ZoneAvoidanceRule实现，该策略能够在多区域环境下选出最佳区域的实例。
• IPing：默认采用DummyPing实现，该检查策略是一个特殊的实现，实际上并不会检查实例是否可用，而是始终返回true,默认认为所有实例都可用。
• ServerList:服务实例清单的维护机制，默认采用ConfigurationBasedServerList实现。
• ServerlistFilter:服务实例清单过滤机制，默认采用ZonePreferenceServerListFilter，该策略能够优先过滤出于请求方处于同区域的服务实例。
• ILoadBalancer:负载均衡器，默认采用ZoneAwareLoadBalancer，它具备区域感知的能力。

上面这些自动化配置仅在没有引入Spring Cloud Eureka等服务治理框架时如此。

 二 源代码解读

@SuppressWarnings("deprecation")
@Configuration
@EnableConfigurationProperties
//Order is important here, last should be the default, first should be optional
// see https://github.com/spring-cloud/spring-cloud-netflix/issues/2086#issuecomment-316281653
@Import({HttpClientConfiguration.class, OkHttpRibbonConfiguration.class, RestClientRibbonConfiguration.class, HttpClientRibbonConfiguration.class})
public class RibbonClientConfiguration {

    public static final int DEFAULT_CONNECT_TIMEOUT = 1000;
    public static final int DEFAULT_READ_TIMEOUT = 1000;

    @RibbonClientName
    private String name = "client";


    @Autowired
    private PropertiesFactory propertiesFactory;

    @Bean
    @ConditionalOnMissingBean
    public IClientConfig ribbonClientConfig() {
        //默认采用DefaultClientConfigImpl实现
        DefaultClientConfigImpl config = new DefaultClientConfigImpl();
        config.loadProperties(this.name);
        config.set(CommonClientConfigKey.ConnectTimeout, DEFAULT_CONNECT_TIMEOUT);
        config.set(CommonClientConfigKey.ReadTimeout, DEFAULT_READ_TIMEOUT);
        return config;
    }

    @Bean
    @ConditionalOnMissingBean
    public IRule ribbonRule(IClientConfig config) {
        if (this.propertiesFactory.isSet(IRule.class, name)) {
            return this.propertiesFactory.get(IRule.class, config, name);
        }
        //默认采用ZoneAvoidanceRule实现，该策略能够在多区域环境下选出最佳区域的实例。
        ZoneAvoidanceRule rule = new ZoneAvoidanceRule();
        rule.initWithNiwsConfig(config);
        return rule;
    }

    @Bean
    @ConditionalOnMissingBean
    public IPing ribbonPing(IClientConfig config) {
        if (this.propertiesFactory.isSet(IPing.class, name)) {
            return this.propertiesFactory.get(IPing.class, config, name);
        }
        //该检查策略是一个特殊的实现，实际上并不会检查实例是否可用，而是始终返回true,默认认为所有实例都可用。
        return new DummyPing();
    }

    @Bean
    @ConditionalOnMissingBean
    @SuppressWarnings("unchecked")
    public ServerList ribbonServerList(IClientConfig config) {
        if (this.propertiesFactory.isSet(ServerList.class, name)) {
            return this.propertiesFactory.get(ServerList.class, config, name);
        }
        //服务实例清单的维护机制，默认采用ConfigurationBasedServerList实现。
        ConfigurationBasedServerList serverList = new ConfigurationBasedServerList();
        serverList.initWithNiwsConfig(config);
        return serverList;
    }

    @Bean
    @ConditionalOnMissingBean
    public ServerListUpdater ribbonServerListUpdater(IClientConfig config) {
        return new PollingServerListUpdater(config);
    }

    @Bean
    @ConditionalOnMissingBean
    public ILoadBalancer ribbonLoadBalancer(IClientConfig config,
            ServerList serverList, ServerListFilter serverListFilter,
            IRule rule, IPing ping, ServerListUpdater serverListUpdater) {
        if (this.propertiesFactory.isSet(ILoadBalancer.class, name)) {
            return this.propertiesFactory.get(ILoadBalancer.class, config, name);
        }
        //负载均衡器，默认采用ZoneAwareLoadBalancer，它具备区域感知的能力。
        return new ZoneAwareLoadBalancer<>(config, rule, ping, serverList,
                serverListFilter, serverListUpdater);
    }

    @Bean
    @ConditionalOnMissingBean
    @SuppressWarnings("unchecked")
    public ServerListFilter ribbonServerListFilter(IClientConfig config) {
        if (this.propertiesFactory.isSet(ServerListFilter.class, name)) {
            return this.propertiesFactory.get(ServerListFilter.class, config, name);
        }
        //服务实例清单过滤机制，默认采用ZonePreferenceServerListFilter，该策略能够优先过滤出
        //于请求方处于同区域的服务实例。
        ZonePreferenceServerListFilter filter = new ZonePreferenceServerListFilter();
        filter.initWithNiwsConfig(config);
        return filter;
    }

    @Bean
    @ConditionalOnMissingBean
    public RibbonLoadBalancerContext ribbonLoadBalancerContext(ILoadBalancer loadBalancer,
                                                               IClientConfig config, RetryHandler retryHandler) {
        return new RibbonLoadBalancerContext(loadBalancer, config, retryHandler);
    }

    @Bean
    @ConditionalOnMissingBean
    public RetryHandler retryHandler(IClientConfig config) {
        return new DefaultLoadBalancerRetryHandler(config);
    }

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

    @PostConstruct
    public void preprocess() {
        setRibbonProperty(name, DeploymentContextBasedVipAddresses.key(), name);
    }

    static class OverrideRestClient extends RestClient {

        private IClientConfig config;
        private ServerIntrospector serverIntrospector;

        protected OverrideRestClient(IClientConfig config,
                ServerIntrospector serverIntrospector) {
            super();
            this.config = config;
            this.serverIntrospector = serverIntrospector;
            initWithNiwsConfig(this.config);
        }

        @Override
        public URI reconstructURIWithServer(Server server, URI original) {
            URI uri = updateToSecureConnectionIfNeeded(original, this.config,
                    this.serverIntrospector, server);
            return super.reconstructURIWithServer(server, uri);
        }

        @Override
        protected Client apacheHttpClientSpecificInitialization() {
            ApacheHttpClient4 apache = (ApacheHttpClient4) super.apacheHttpClientSpecificInitialization();
            apache.getClientHandler().getHttpClient().getParams().setParameter(
                    ClientPNames.COOKIE_POLICY, CookiePolicy.IGNORE_COOKIES);
            return apache;
        }

    }

}