Nacos 集成 Ribbon 客戶端負載均衡源碼分析

Spring Cloud Nacos & Ribbon

Nacos 爲了適應 Spring Cloud 技術棧和在 Spring Cloud Alibaba 之前的 Spring Cloud Netflix 技術棧保持兼容，所以 Nacos 需要實現和 Spring Cloud Netfilx Ribbon 的集成，用在服務發現，以及服務到服務之間的調用功能。

核心源碼分析

NacosRibbonClientConfiguration

@Configuration(proxyBeanMethods = false)
@ConditionalOnRibbonNacos
public class NacosRibbonClientConfiguration {

	@Autowired
	private PropertiesFactory propertiesFactory;

	// 實例化一個 ServerList 實例 ，該實例類爲 NacosServerList 實現了 com.netflix.loadbalancer.ServerList 接口
	@Bean
	@ConditionalOnMissingBean
	public ServerList<?> ribbonServerList(IClientConfig config,
			NacosDiscoveryProperties nacosDiscoveryProperties) {
		if (this.propertiesFactory.isSet(ServerList.class, config.getClientName())) {
			ServerList serverList = this.propertiesFactory.get(ServerList.class, config,
					config.getClientName());
			return serverList;
		}
		NacosServerList serverList = new NacosServerList(nacosDiscoveryProperties);
		serverList.initWithNiwsConfig(config);
		return serverList;
	}

	@Bean
	@ConditionalOnMissingBean
	public NacosServerIntrospector nacosServerIntrospector() {
		return new NacosServerIntrospector();
	}

}

com.netflix.loadbalancer.ServerList 提供客戶端負載均衡功能

public interface ServerList<T extends Server> {

    public List<T> getInitialListOfServers();
    
    /**
     * Return updated list of servers. This is called say every 30 secs
     * (configurable) by the Loadbalancer's Ping cycle
     * 
     */
    public List<T> getUpdatedListOfServers();   

}

com.alibaba.cloud.nacos.ribbon.NacosServerList

public class NacosServerList extends AbstractServerList<NacosServer> {

	@Override
	public List<NacosServer> getInitialListOfServers() {
		return getServers();
	}

	@Override
	public List<NacosServer> getUpdatedListOfServers() {
		return getServers();
	}

	// 該類中的核心代碼獲取到服務實例列表
	private List<NacosServer> getServers() {
		try {
			String group = discoveryProperties.getGroup();
			// namingServiceInstance() 獲取到 NamingService 實例對象 ， NamingService 提供了使用 http 協議和 Nacos Server 端通信的功能
			List<Instance> instances = discoveryProperties.namingServiceInstance()
					.selectInstances(serviceId, group, true);
			return instancesToServerList(instances);
		}
		catch (Exception e) {
			throw new IllegalStateException(
					"Can not get service instances from nacos, serviceId=" + serviceId,
					e);
		}
	}
}

com.alibaba.cloud.nacos.NacosDiscoveryProperties

@ConfigurationProperties("spring.cloud.nacos.discovery")
public class NacosDiscoveryProperties {

	// 創建或者獲取一個已有的 NamingService 實例
	public NamingService namingServiceInstance() {

		if (null != namingService) {
			return namingService;
		}

		try {
			namingService = NacosFactory.createNamingService(getNacosProperties());
		}
		catch (Exception e) {
			log.error("create naming service error!properties={},e=,", this, e);
			return null;
		}
		return namingService;
	}
}

com.alibaba.nacos.client.naming.NacosNamingService

@SuppressWarnings("PMD.ServiceOrDaoClassShouldEndWithImplRule")
public class NacosNamingService implements NamingService {

	// 查詢服務實例列表
    @Override
    public List<Instance> selectInstances(String serviceName, String groupName, List<String> clusters, boolean healthy, boolean subscribe) throws NacosException {

        ServiceInfo serviceInfo;
        if (subscribe) {
            serviceInfo = hostReactor.getServiceInfo(NamingUtils.getGroupedName(serviceName, groupName), StringUtils.join(clusters, ","));
        } else {
            serviceInfo = hostReactor.getServiceInfoDirectlyFromServer(NamingUtils.getGroupedName(serviceName, groupName), StringUtils.join(clusters, ","));
        }
        return selectInstances(serviceInfo, healthy);
    }
}

com.alibaba.nacos.client.naming.core.HostReactor

public class HostReactor {

	public ServiceInfo getServiceInfo(final String serviceName, final String clusters) {

        NAMING_LOGGER.debug("failover-mode: " + failoverReactor.isFailoverSwitch());
        String key = ServiceInfo.getKey(serviceName, clusters);
        if (failoverReactor.isFailoverSwitch()) {
            return failoverReactor.getService(key);
        }

        ServiceInfo serviceObj = getServiceInfo0(serviceName, clusters);

        if (null == serviceObj) {
            serviceObj = new ServiceInfo(serviceName, clusters);

            serviceInfoMap.put(serviceObj.getKey(), serviceObj);

            updatingMap.put(serviceName, new Object());
            updateServiceNow(serviceName, clusters);
            updatingMap.remove(serviceName);

        } else if (updatingMap.containsKey(serviceName)) {

            if (UPDATE_HOLD_INTERVAL > 0) {
                // hold a moment waiting for update finish
                synchronized (serviceObj) {
                    try {
                        serviceObj.wait(UPDATE_HOLD_INTERVAL);
                    } catch (InterruptedException e) {
                        NAMING_LOGGER.error("[getServiceInfo] serviceName:" + serviceName + ", clusters:" + clusters, e);
                    }
                }
            }
        }

        scheduleUpdateIfAbsent(serviceName, clusters);

        return serviceInfoMap.get(serviceObj.getKey());
    }
	
	// 去 nacos server 端查詢服務實列信息更新本地 jvm 內存的中服務實例信息，存儲服務實例信息到本機硬盤
	public void updateServiceNow(String serviceName, String clusters) {
        ServiceInfo oldService = getServiceInfo0(serviceName, clusters);
        try {

            String result = serverProxy.queryList(serviceName, clusters, pushReceiver.getUDPPort(), false);

            if (StringUtils.isNotEmpty(result)) {
				// 具體如何處理從 nacos server 返回的服務實列信息數據看這個函數
                processServiceJSON(result);
            }
        } catch (Exception e) {
            NAMING_LOGGER.error("[NA] failed to update serviceName: " + serviceName, e);
        } finally {
            if (oldService != null) {
                synchronized (oldService) {
                    oldService.notifyAll();
                }
            }
        }
    }
	
	// 開啓異步從 nacas server 查詢更新本地 jvm 內存中的服務實例信息任務
	public void scheduleUpdateIfAbsent(String serviceName, String clusters) {
        if (futureMap.get(ServiceInfo.getKey(serviceName, clusters)) != null) {
            return;
        }

        synchronized (futureMap) {
            if (futureMap.get(ServiceInfo.getKey(serviceName, clusters)) != null) {
                return;
            }

            ScheduledFuture<?> future = addTask(new UpdateTask(serviceName, clusters));
            futureMap.put(ServiceInfo.getKey(serviceName, clusters), future);
        }
    }
}

com.alibaba.nacos.client.naming.core.HostReactor.UpdateTask

public class UpdateTask implements Runnable {
        long lastRefTime = Long.MAX_VALUE;
        private String clusters;
        private String serviceName;

        public UpdateTask(String serviceName, String clusters) {
            this.serviceName = serviceName;
            this.clusters = clusters;
        }

        @Override
        public void run() {
            try {
                ServiceInfo serviceObj = serviceInfoMap.get(ServiceInfo.getKey(serviceName, clusters));

                if (serviceObj == null) {
                    updateServiceNow(serviceName, clusters);
                    executor.schedule(this, DEFAULT_DELAY, TimeUnit.MILLISECONDS);
                    return;
                }

                if (serviceObj.getLastRefTime() <= lastRefTime) {
                    updateServiceNow(serviceName, clusters);
                    serviceObj = serviceInfoMap.get(ServiceInfo.getKey(serviceName, clusters));
                } else {
                    // if serviceName already updated by push, we should not override it
                    // since the push data may be different from pull through force push
                    refreshOnly(serviceName, clusters);
                }

                lastRefTime = serviceObj.getLastRefTime();

                if (!eventDispatcher.isSubscribed(serviceName, clusters) &&
                    !futureMap.containsKey(ServiceInfo.getKey(serviceName, clusters))) {
                    // abort the update task:
                    NAMING_LOGGER.info("update task is stopped, service:" + serviceName + ", clusters:" + clusters);
                    return;
                }

                executor.schedule(this, serviceObj.getCacheMillis(), TimeUnit.MILLISECONDS);


            } catch (Throwable e) {
                NAMING_LOGGER.warn("[NA] failed to update serviceName: " + serviceName, e);
            }

        }