SpringCloud解析九：Consul与Ribbon集成原理

在这里我们讨论下Consul与Ribbon的集成过程，以spring-cloud-consul-discovery-2.2.0.RELEASE.jar为例。在该包的/META-INF/spring.factories中包含了如下的内容

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.consul.discovery.RibbonConsulAutoConfiguration,\
org.springframework.cloud.consul.discovery.configclient.ConsulConfigServerAutoConfiguration,\
org.springframework.cloud.consul.serviceregistry.ConsulAutoServiceRegistrationAutoConfiguration,\
org.springframework.cloud.consul.serviceregistry.ConsulServiceRegistryAutoConfiguration,\
org.springframework.cloud.consul.discovery.ConsulDiscoveryClientConfiguration,\
org.springframework.cloud.consul.discovery.reactive.ConsulReactiveDiscoveryClientConfiguration,\
org.springframework.cloud.consul.discovery.ConsulCatalogWatchAutoConfiguration, \
org.springframework.cloud.consul.support.ConsulHeartbeatAutoConfiguration
org.springframework.cloud.bootstrap.BootstrapConfiguration=\
org.springframework.cloud.consul.discovery.configclient.ConsulDiscoveryClientConfigServiceBootstrapConfiguration

这里的RibbonConsulAutoConfiguration便是入口。该配置类定义如下：

@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties
@ConditionalOnConsulEnabled
@ConditionalOnBean(SpringClientFactory.class)
@ConditionalOnProperty(value = "spring.cloud.consul.ribbon.enabled",
        matchIfMissing = true)
@AutoConfigureAfter(RibbonAutoConfiguration.class)
@RibbonClients(defaultConfiguration = ConsulRibbonClientConfiguration.class)
public class RibbonConsulAutoConfiguration {

}

从上代码可得到以下信息
1）该配置类在RibbonAutoConfiguration之后执行
2）修改Ribbon的默认配置为ConsulRibbonClientConfiguration

接着把目光转向ConsulRibbonClientConfiguration，该类定义如下：

@Configuration(proxyBeanMethods = false)
public class ConsulRibbonClientConfiguration {

    protected static final String VALUE_NOT_SET = "__not__set__";

    protected static final String DEFAULT_NAMESPACE = "ribbon";

    @Autowired
    private ConsulClient client;

    @Value("${ribbon.client.name}")
    private String serviceId = "client";

    public ConsulRibbonClientConfiguration() {
    }

    public ConsulRibbonClientConfiguration(String serviceId) {
        this.serviceId = serviceId;
    }

    @Bean
    @ConditionalOnMissingBean
    public ServerList<?> ribbonServerList(IClientConfig config,
            ConsulDiscoveryProperties properties) {
        ConsulServerList serverList = new ConsulServerList(this.client, properties);
        serverList.initWithNiwsConfig(config);
        return serverList;
    }

    @Bean
    @ConditionalOnMissingBean
    public ServerListFilter<Server> ribbonServerListFilter() {
        return new HealthServiceServerListFilter();
    }

    @Bean
    @ConditionalOnMissingBean
    public IPing ribbonPing() {
        return new ConsulPing();
    }

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

    @PostConstruct
    public void preprocess() {
        setProp(this.serviceId, DeploymentContextBasedVipAddresses.key(), this.serviceId);
        setProp(this.serviceId, EnableZoneAffinity.key(), "true");
    }

    protected void setProp(String serviceId, String suffix, String value) {
        // how to set the namespace properly?
        String key = getKey(serviceId, suffix);
        DynamicStringProperty property = getProperty(key);
        if (property.get().equals(VALUE_NOT_SET)) {
            ConfigurationManager.getConfigInstance().setProperty(key, value);
        }
    }

    protected DynamicStringProperty getProperty(String key) {
        return DynamicPropertyFactory.getInstance().getStringProperty(key, VALUE_NOT_SET);
    }

    protected String getKey(String serviceId, String suffix) {
        return serviceId + "." + DEFAULT_NAMESPACE + "." + suffix;
    }

}

在这个类里面重写了Ribbon默认配置里面的ServerList、ServerListFilter、IPing 和ConsulServerIntrospector 。 在以前章节的分析中我们知道，Ribbon的客户端是在第一次调用的时候被创建，也就是在这里重写的这些默认配置会在第一次调用的时候被使用，从而将Consul的发现机制应用到了Ribbon中。

注意：在Ribbon我们还可以配置将指定的服务非延迟创建，对于配置了非延迟创建的Ribbon客户端是否还能生效呢？因为Ribbon客户端的非延迟创建是在应用程序启动后才立即执行，所以依然生效。