七、Nacos源码系列：Nacos服务发现
目录
一、服务发现
二、getServices()：获取服务列表
2.1、获取服务列表
2.2、总结图
三、getInstances(serviceId)：获取服务实例列表
3.1、从缓存中获取服务信息
3.2、缓存为空，执行订阅服务
3.2.1、调度更新，往线程池中提交一个UpdateTask任务
3.2.2、订阅服务
3.2.3、处理服务信息
3.3、非订阅模式，通过grpc发送ServiceQueryRequest服务查询请求
3.4、筛选满足条件的实例
3.5、总结图
一、服务发现
在discovery-provider项目的pom.xml中，我们引入了如下依赖：
com.alibaba.cloud
spring-cloud-starter-alibaba-nacos-discovery
2.2.9.RELEASE
SpringCloud很多功能都是基于SpringBoot项目的自动配置原理来扩展实现的，下面我们查看spring-cloud-starter-alibaba-nacos-discovery-2.2.9.RELEASE.jar包路径下的spring.factories的"org.springframework.boot.autoconfigure.EnableAutoConfiguration"自动装配类配置，如下图：
如上图，跟客户端服务发现有关的有两个自动配置类：NacosDiscoveryClientConfiguration和NacosDiscoveryAutoConfiguration。
相关源码如下：
@Configuration(proxyBeanMethods = false)
@ConditionalOnDiscoveryEnabled
@ConditionalOnBlockingDiscoveryEnabled
@ConditionalOnNacosDiscoveryEnabled
@AutoConfigureBefore({ SimpleDiscoveryClientAutoConfiguration.class,
CommonsClientAutoConfiguration.class })
// 在NacosDiscoveryAutoConfiguration自动装配类执行完成后才执行
@AutoConfigureAfter(NacosDiscoveryAutoConfiguration.class)
public class NacosDiscoveryClientConfiguration {
// 创建DiscoveryClient bean对象
@Bean
public DiscoveryClient nacosDiscoveryClient(
NacosServiceDiscovery nacosServiceDiscovery) {
return new NacosDiscoveryClient(nacosServiceDiscovery);
}
@Bean
@ConditionalOnMissingBean
@ConditionalOnProperty(value = "spring.cloud.nacos.discovery.watch.enabled",
matchIfMissing = true)
public NacosWatch nacosWatch(NacosServiceManager nacosServiceManager,
NacosDiscoveryProperties nacosDiscoveryProperties) {
return new NacosWatch(nacosServiceManager, nacosDiscoveryProperties);
}
}
@Configuration(proxyBeanMethods = false)
// spring.cloud.discovery.enabled=true时才生效,缺省值为true
@ConditionalOnDiscoveryEnabled
// spring.cloud.nacos.discovery.enabled=true时才生效,缺省值为true
@ConditionalOnNacosDiscoveryEnabled
public class NacosDiscoveryAutoConfiguration {
@Bean
@ConditionalOnMissingBean
public NacosDiscoveryProperties nacosProperties() {
// 匹配配置文件中以“spring.cloud.nacos.discovery”为前缀的那些属性，
// 如namespace、username、password、serverAddr等属性
return new NacosDiscoveryProperties();
}
// 创建NacosServiceDiscovery bean对象
@Bean
@ConditionalOnMissingBean
public NacosServiceDiscovery nacosServiceDiscovery(
NacosDiscoveryProperties discoveryProperties,
NacosServiceManager nacosServiceManager) {
return new NacosServiceDiscovery(discoveryProperties, nacosServiceManager);
}
}在NacosDiscoveryAutoConfiguration自动配置类中，创建了一个NacosServiceDiscovery的bean对象，然后在NacosDiscoveryClientConfiguration自动装配时，创建DiscoveryClient的bean对象，传入前面创建的NacosServiceDiscovery对象。
重点关注NacosDiscoveryClient这个类，NacosDiscoveryClient的源码如下：
public class NacosDiscoveryClient implements DiscoveryClient {
private static final Logger log = LoggerFactory.getLogger(NacosDiscoveryClient.class);
/**
* Nacos Discovery Client Description.
*/
public static final String DESCRIPTION = "Spring Cloud Nacos Discovery Client";
private NacosServiceDiscovery serviceDiscovery;
public NacosDiscoveryClient(NacosServiceDiscovery nacosServiceDiscovery) {
this.serviceDiscovery = nacosServiceDiscovery;
}
@Override
public String description() {
return DESCRIPTION;
}
@Override
public List getInstances(String serviceId) {
try {
return serviceDiscovery.getInstances(serviceId);
}
catch (Exception e) {
throw new RuntimeException(
"Can not get hosts from nacos server. serviceId: " + serviceId, e);
}
}
@Override
public List getServices() {
try {
return serviceDiscovery.getServices();
}
catch (Exception e) {
log.error("get service name from nacos server fail,", e);
return Collections.emptyList();
}
}
} 可以看到，NacosDiscoveryClient实现了SpringCloud的DiscoveryClient接口，重点是getInstances()和getServices()方法，而且都是由NacosServiceDiscovery类去实现。
public class NacosServiceDiscovery {
// 跟配置文件中以“spring.cloud.nacos.discovery”前缀的属性配置对应上
private NacosDiscoveryProperties discoveryProperties;
// nacos服务管理器对象
private NacosServiceManager nacosServiceManager;
public NacosServiceDiscovery(NacosDiscoveryProperties discoveryProperties,
NacosServiceManager nacosServiceManager) {
this.discoveryProperties = discoveryProperties;
this.nacosServiceManager = nacosServiceManager;
}
/**
* 返回指定group和servic的所有实例
*/
public List getInstances(String serviceId) throws NacosException {
// 配置文件中配置的group组名
String group = discoveryProperties.getGroup();
// namingService(): 通过反射创建一个NacosNamingService对象
// 最终会调用NacosNamingService#selectInstances()方法
List instances = namingService().selectInstances(serviceId, group,
true);
// 将Instance包装成NacosServiceInstance对象返回
return hostToServiceInstanceList(instances, serviceId);
}
/**
* 返回指定group的所有服务名称
*/
public List getServices() throws NacosException {
// 配置文件中配置的group组名
String group = discoveryProperties.getGroup();
// namingService(): 通过反射创建一个NacosNamingService对象
// 最终会调用NamingGrpcClientProxy#getServiceList()方法
ListView services = namingService().getServicesOfServer(1,
Integer.MAX_VALUE, group);
// 返回所有服务名称
return services.getData();
}
public static List hostToServiceInstanceList(
List instances, String serviceId) {
List result = new ArrayList<>(instances.size());
for (Instance instance : instances) {
ServiceInstance serviceInstance = hostToServiceInstance(instance, serviceId);
if (serviceInstance != null) {
result.add(serviceInstance);
}
}
return result;
}
public static ServiceInstance hostToServiceInstance(Instance instance,
String serviceId) {
if (instance == null || !instance.isEnabled() || !instance.isHealthy()) {
return null;
}
NacosServiceInstance nacosServiceInstance = new NacosServiceInstance();
nacosServiceInstance.setHost(instance.getIp());
nacosServiceInstance.setPort(instance.getPort());
nacosServiceInstance.setServiceId(serviceId);
Map metadata = new HashMap<>();
metadata.put("nacos.instanceId", instance.getInstanceId());
metadata.put("nacos.weight", instance.getWeight() + "");
metadata.put("nacos.healthy", instance.isHealthy() + "");
metadata.put("nacos.cluster", instance.getClusterName() + "");
if (instance.getMetadata() != null) {
metadata.putAll(instance.getMetadata());
}
metadata.put("nacos.ephemeral", String.valueOf(instance.isEphemeral()));
nacosServiceInstance.setMetadata(metadata);
if (metadata.containsKey("secure")) {
boolean secure = Boolean.parseBoolean(metadata.get("secure"));
nacosServiceInstance.setSecure(secure);
}
return nacosServiceInstance;
}
private NamingService namingService() {
return nacosServiceManager.getNamingService();
}
} 接下来，我们分析前面介绍到的两个重要方法：getInstances(serviceId)和getServices()。
二、getServices()：获取服务列表
2.1、获取服务列表
// namingService(): 通过反射创建一个NacosNamingService对象
// NamingFactory#createNamingService(java.util.Properties)
public static NamingService createNamingService(Properties properties) throws NacosException {
try {
Class driverImplClass = Class.forName("com.alibaba.nacos.client.naming.NacosNamingService");
Constructor constructor = driverImplClass.getConstructor(Properties.class);
return (NamingService) constructor.newInstance(properties);
} catch (Throwable e) {
throw new NacosException(NacosException.CLIENT_INVALID_PARAM, e);
}
}//getServices()调用栈大体如下：
namingService().getServicesOfServer(1, Integer.MAX_VALUE, group);
NacosNamingService#getServicesOfServer
clientProxy.getServiceList(pageNo, pageSize, groupName, selector)
NamingClientProxyDelegate#getServiceList
grpcClientProxy.getServiceList(pageNo, pageSize, groupName, selector);
// 最终会调用NamingGrpcClientProxy#getServiceList()方法
public ListView getServiceList(int pageNo, int pageSize, String groupName, AbstractSelector selector)
throws NacosException {
// 构建ServiceListRequest请求（服务列表请求），指定命名空间ID、服务组名
ServiceListRequest request = new ServiceListRequest(namespaceId, groupName, pageNo, pageSize);
if (selector != null) {
if (SelectorType.valueOf(selector.getType()) == SelectorType.label) {
request.setSelector(JacksonUtils.toJson(selector));
}
}
// 发送服务列表请求给Nacos服务端，接下来由服务端处理
ServiceListResponse response = requestToServer(request, ServiceListResponse.class);
// 组装返回值出去
ListView result = new ListView<>();
result.setCount(response.getCount());
result.setData(response.getServiceNames());
return result;
} 接下来，我们看看服务端怎么处理这个服务列表请求的。通过对ServiceListRequest类引用的追踪，我们发现是在com.alibaba.nacos.naming.remote.rpc.handler.ServiceListRequestHandler#handle这个方法中对客户端提交的服务列表请求进行处理的。
// 处理客户端提交的服务列表请求
public ServiceListResponse handle(ServiceListRequest request, RequestMeta meta) throws NacosException {
// ServiceManager.getInstance()通过单例返回一个ServiceManager对象
/**
* 获取指定命令空间下的所有服务，在ServiceManager中存在一个map保存着每个命名空间中的所有服务。
* ConcurrentHashMap> namespaceSingletonMaps = new ConcurrentHashMap<>(1 << 2)
* key: namespaceId
* value: Set
* 注册实例的时候，就往这个map写入了数据
*
* ServiceManager.getInstance().getSingletons(request.getNamespace())相当于执行：
* namespaceSingletonMaps.getOrDefault(namespace, new HashSet<>(1))
*/
Collection serviceSet = ServiceManager.getInstance().getSingletons(request.getNamespace());
// 构建响应结果
ServiceListResponse result = ServiceListResponse.buildSuccessResponse(0, new LinkedList<>());
if (!serviceSet.isEmpty()) {
// 过滤指定分组的Service，添加groupServiceName，格式如：groupA@@serviceA
Collection serviceNameSet = selectServiceWithGroupName(serviceSet, request.getGroupName());
// 按分页裁剪serviceNameSet
List serviceNameList = ServiceUtil
.pageServiceName(request.getPageNo(), request.getPageSize(), serviceNameSet);
result.setCount(serviceNameSet.size());
result.setServiceNames(serviceNameList);
}
return result;
} 从源码可以看出，Nacos服务端从ServiceManager管理器中的一个map（namespaceSingletonMaps）中拿出指定命名空间那些Service，并根据筛选条件过滤满足条件的Service，然后组装好groupServiceName（格式如：groupA@@serviceA）并返回。
2.2、总结图
三、getInstances(serviceId)：获取服务实例列表
// 调用栈如下：
// namingService().selectInstances(serviceId, group,true);
// NamingService#selectInstances(serviceName, groupName, healthy, true)
// NamingService#selectInstances(serviceName, groupName, new ArrayList(), healthy, true)
// getInstances(serviceId)方法最终会调用NacosNamingService#selectInstances()获取实例信息。 public List selectInstances(String serviceName, String groupName, List clusters, boolean healthy,
boolean subscribe) throws NacosException {
ServiceInfo serviceInfo;
// 集群名称,使用逗号分隔
String clusterString = StringUtils.join(clusters, ",");
// 是否订阅，默认是订阅的
if (subscribe) {
/**
* 1.从缓存中获取ServiceInfo
* ConcurrentMap serviceInfoMap
* key: groupName@@serviceName 或者 groupName@@serviceName@@clusterString
* value: ServiceInfo
*/
// 示例：serviceName=discovery-provider groupName=DEFAULT_GROUP
serviceInfo = serviceInfoHolder.getServiceInfo(serviceName, groupName, clusterString);
// 2.缓存为空，执行订阅服务
if (null == serviceInfo) {
serviceInfo = clientProxy.subscribe(serviceName, groupName, clusterString);
}
} else {
// 3.非订阅，通过grpc发送ServiceQueryRequest服务查询请求
serviceInfo = clientProxy.queryInstancesOfService(serviceName, groupName, clusterString, 0, false);
}
// 4.筛选满足条件的实例
return selectInstances(serviceInfo, healthy);
} 上述流程的基本逻辑为：
- 如果是订阅模式，则直接从本地缓存获取服务信息（ServiceInfo），然后从中获取实例列表，这是因为订阅机制会自动同步服务器实例的变化到本地。如果本地缓存中没有，那说明是首次调用，则进行订阅，在订阅完成后会获得到服务信息。
- 如果是非订阅模式，那就直接请求服务器端，获得服务信息。
3.1、从缓存中获取服务信息
public ServiceInfo getServiceInfo(final String serviceName, final String groupName, final String clusters) {
NAMING_LOGGER.debug("failover-mode: {}", failoverReactor.isFailoverSwitch());
// 组装服务名(带组名)：groupName@@serviceName
// 例如：DEFAULT_GROUP@@discovery-provider
String groupedServiceName = NamingUtils.getGroupedName(serviceName, groupName);
// 如果指定了集群，那么key还会加上"@@clusters"
String key = ServiceInfo.getKey(groupedServiceName, clusters);
if (failoverReactor.isFailoverSwitch()) {
return failoverReactor.getService(key);
}
// ConcurrentMap serviceInfoMap
// 从缓存中获取服务信息
return serviceInfoMap.get(key);
} 3.2、缓存为空，执行订阅服务
serviceInfo = clientProxy.subscribe(serviceName, groupName, clusterString);
// clientProxy在构造方法中初始化为：NamingClientProxyDelegate
this.clientProxy = new NamingClientProxyDelegate(this.namespace, serviceInfoHolder, nacosClientProperties, changeNotifier);实际上调用的是NamingClientProxyDelegate#subscribe()方法：
public ServiceInfo subscribe(String serviceName, String groupName, String clusters) throws NacosException {
NAMING_LOGGER.info("[SUBSCRIBE-SERVICE] service:{}, group:{}, clusters:{} ", serviceName, groupName, clusters);
// 服务名称（带组名） 格式：groupName@@serviceName
String serviceNameWithGroup = NamingUtils.getGroupedName(serviceName, groupName);
// 如果集群名称非空，key还需要拼接上集群名称
String serviceKey = ServiceInfo.getKey(serviceNameWithGroup, clusters);
// 调度更新，往线程池中提交一个UpdateTask任务
serviceInfoUpdateService.scheduleUpdateIfAbsent(serviceName, groupName, clusters);
// 获取缓存中的服务信息
ServiceInfo result = serviceInfoHolder.getServiceInfoMap().get(serviceKey);
if (null == result || !isSubscribed(serviceName, groupName, clusters)) {
// 缓存中不存在对应的服务信息 或者 SubscriberRedoData还未注册，则执行订阅
result = grpcClientProxy.subscribe(serviceName, groupName, clusters);
}
// 处理服务信息：获取老的服务信息，将新的服务信息重新存入客户端缓存中，对比新的服务信息，如发生变更，则发布实例变更数据，并同步serviceInfo数据到本地文件
serviceInfoHolder.processServiceInfo(result);
return result;
}主要逻辑有下面三个，分析如下。
3.2.1、调度更新，往线程池中提交一个UpdateTask任务
public void scheduleUpdateIfAbsent(String serviceName, String groupName, String clusters) {
if (!asyncQuerySubscribeService) {
return;
}
// 组装key 格式：groupName@@serviceName@@clusters
String serviceKey = ServiceInfo.getKey(NamingUtils.getGroupedName(serviceName, groupName), clusters);
// Map> futureMap = new HashMap<>()
// futureMap用于保存UpdateTask线程池任务的执行结果
if (futureMap.get(serviceKey) != null) {
return;
}
synchronized (futureMap) {
// double check双重检查，如果非空，直接返回，也就是相同的groupName@@serviceName@@clusters，只会存在一个UpdateTask任务
if (futureMap.get(serviceKey) != null) {
return;
}
// 往线程池中添加一个更新任务
// UpdateTask实现了Runnable接口，需要关注其run()方法
ScheduledFuture future = addTask(new UpdateTask(serviceName, groupName, clusters));
futureMap.put(serviceKey, future);
}
}
private synchronized ScheduledFuture addTask(UpdateTask task) {
// 延迟1s执行UpdateTask
return executor.schedule(task, DEFAULT_DELAY, TimeUnit.MILLISECONDS);
} 可以看到，使用了一个map来保存线程池任务的响应，延迟1s执行调度更新任务。我们看下UpdateTask的源码：
public class UpdateTask implements Runnable {
long lastRefTime = Long.MAX_VALUE;
private boolean isCancel;
private final String serviceName;
private final String groupName;
private final String clusters;
private final String groupedServiceName;
private final String serviceKey;
/**
* the fail situation. 1:can't connect to server 2:serviceInfo's hosts is empty
*/
private int failCount = 0;
public UpdateTask(String serviceName, String groupName, String clusters) {
this.serviceName = serviceName;
this.groupName = groupName;
this.clusters = clusters;
this.groupedServiceName = NamingUtils.getGroupedName(serviceName, groupName);
this.serviceKey = ServiceInfo.getKey(groupedServiceName, clusters);
}
@Override
public void run() {
long delayTime = DEFAULT_DELAY;
try {
if (!changeNotifier.isSubscribed(groupName, serviceName, clusters) && !futureMap.containsKey(
serviceKey)) {
NAMING_LOGGER.info("update task is stopped, service:{}, clusters:{}", groupedServiceName, clusters);
isCancel = true;
return;
}
ServiceInfo serviceObj = serviceInfoHolder.getServiceInfoMap().get(serviceKey);
if (serviceObj == null) {
// 使用grpc向服务端发送ServiceQueryRequest服务查询请求
serviceObj = namingClientProxy.queryInstancesOfService(serviceName, groupName, clusters, 0, false);
// 处理服务信息：获取老的服务信息，将新的服务信息重新存入客户端缓存中，对比新的服务信息，如发生变更，则发布实例变更数据，并同步serviceInfo数据到本地文件
serviceInfoHolder.processServiceInfo(serviceObj);
lastRefTime = serviceObj.getLastRefTime();
return;
}
if (serviceObj.getLastRefTime() <= lastRefTime) {
// 使用grpc向服务端发送ServiceQueryRequest服务查询请求
serviceObj = namingClientProxy.queryInstancesOfService(serviceName, groupName, clusters, 0, false);
// 处理服务信息：获取老的服务信息，将新的服务信息重新存入客户端缓存中，对比新的服务信息，如发生变更，则发布实例变更数据，并同步serviceInfo数据到本地文件
serviceInfoHolder.processServiceInfo(serviceObj);
}
lastRefTime = serviceObj.getLastRefTime();
if (CollectionUtils.isEmpty(serviceObj.getHosts())) {
// 记录失败次数
incFailCount();
return;
}
// TODO multiple time can be configured.
delayTime = serviceObj.getCacheMillis() * DEFAULT_UPDATE_CACHE_TIME_MULTIPLE;
// 重置失败次数
resetFailCount();
} catch (NacosException e) {
handleNacosException(e);
} catch (Throwable e) {
handleUnknownException(e);
} finally {
if (!isCancel) {
// 注意：延时时间最长为60s，时长和失败次数相关（失败次数越大，延时时间越长）
executor.schedule(this, Math.min(delayTime << failCount, DEFAULT_DELAY * 60),
TimeUnit.MILLISECONDS);
}
}
}
private void handleNacosException(NacosException e) {
incFailCount();
int errorCode = e.getErrCode();
if (NacosException.SERVER_ERROR == errorCode) {
handleUnknownException(e);
}
NAMING_LOGGER.warn("Can't update serviceName: {}, reason: {}", groupedServiceName, e.getErrMsg());
}
private void handleUnknownException(Throwable throwable) {
incFailCount();
NAMING_LOGGER.warn("[NA] failed to update serviceName: {}", groupedServiceName, throwable);
}
private void incFailCount() {
int limit = 6;
if (failCount == limit) {
return;
}
failCount++;
}
private void resetFailCount() {
failCount = 0;
}
}run()方法主要逻辑就是使用grpc向服务端发送ServiceQueryRequest服务查询请求，然后处理服务信息，获取老的服务信息，将新的服务信息重新存入客户端缓存中，对比新的服务信息，如发生变更，则发布实例变更数据，并同步serviceInfo数据到本地文件。
这里有重试机制，最多重试6次，延时时间最长为60s，时长和失败次数相关（失败次数越大，延时时间越长）。
3.2.2、订阅服务
public ServiceInfo subscribe(String serviceName, String groupName, String clusters) throws NacosException {
if (NAMING_LOGGER.isDebugEnabled()) {
NAMING_LOGGER.debug("[GRPC-SUBSCRIBE] service:{}, group:{}, cluster:{} ", serviceName, groupName, clusters);
}
// 缓存SubscriberRedoData重做数据，定时使用redoData重新订阅，
// 具体实现在RedoScheduledTask(由NamingGrpcRedoService定时调度)，最终调用的也是NamingGrpcClientProxy#doSubscribe
// 缓存重做数据保存在map中：private final ConcurrentMap subscribes = new ConcurrentHashMap<>();
redoService.cacheSubscriberForRedo(serviceName, groupName, clusters);
// 使用grpc发送服务订阅请求
return doSubscribe(serviceName, groupName, clusters);
}
public void cacheSubscriberForRedo(String serviceName, String groupName, String cluster) {
String key = ServiceInfo.getKey(NamingUtils.getGroupedName(serviceName, groupName), cluster);
SubscriberRedoData redoData = SubscriberRedoData.build(serviceName, groupName, cluster);
// private final ConcurrentMap subscribes = new ConcurrentHashMap<>();
synchronized (subscribes) {
subscribes.put(key, redoData);
}
} 订阅服务首先会缓存SubscriberRedoData重做数据，实际上就是保存在一个map中，后续可以定时使用SubscriberRedoData重做数据来重新订阅，然后使用grpc发送服务订阅请求。
我们来看下如何订阅服务的。
public ServiceInfo doSubscribe(String serviceName, String groupName, String clusters) throws NacosException {
// 构建一个SubscribeServiceRequest客户端订阅请求
// 服务端处理代码: com.alibaba.nacos.naming.remote.rpc.handler.SubscribeServiceRequestHandler.handle
SubscribeServiceRequest request = new SubscribeServiceRequest(namespaceId, groupName, serviceName, clusters,
true);
// grpc请求Nacos服务端进行订阅
SubscribeServiceResponse response = requestToServer(request, SubscribeServiceResponse.class);
// 标记SubscriberRedoData重做数据为已订阅
redoService.subscriberRegistered(serviceName, groupName, clusters);
return response.getServiceInfo();
}通过grpc向Nacos服务端发起一个订阅请求，服务端真正的处理是在：com.alibaba.nacos.naming.remote.rpc.handler.SubscribeServiceRequestHandler#handle()方法。
public SubscribeServiceResponse handle(SubscribeServiceRequest request, RequestMeta meta) throws NacosException {
String namespaceId = request.getNamespace();
String serviceName = request.getServiceName();
String groupName = request.getGroupName();
String app = request.getHeader("app", "unknown");
String groupedServiceName = NamingUtils.getGroupedName(serviceName, groupName);
// 构建一个Service服务，指定为临时实例
Service service = Service.newService(namespaceId, groupName, serviceName, true);
// 构建Subscriber订阅者对象
Subscriber subscriber = new Subscriber(meta.getClientIp(), meta.getClientVersion(), app, meta.getClientIp(),
namespaceId, groupedServiceName, 0, request.getClusters());
// serviceStorage.getData(service): 从缓存中获取serviceInfo
// metadataManager.getServiceMetadata(service).orElse(null): 从内存(map)获取ServiceMetadata
// ServiceUtil.selectInstancesWithHealthyProtection(): 仅包含有保护机制的健康实例
ServiceInfo serviceInfo = ServiceUtil.selectInstancesWithHealthyProtection(serviceStorage.getData(service),
metadataManager.getServiceMetadata(service).orElse(null), subscriber.getCluster(), false,
true, subscriber.getIp());
if (request.isSubscribe()) {
// 订阅服务
clientOperationService.subscribeService(service, subscriber, meta.getConnectionId());
NotifyCenter.publishEvent(new SubscribeServiceTraceEvent(System.currentTimeMillis(),
meta.getClientIp(), service.getNamespace(), service.getGroup(), service.getName()));
} else {
// 取消订阅服务
clientOperationService.unsubscribeService(service, subscriber, meta.getConnectionId());
NotifyCenter.publishEvent(new UnsubscribeServiceTraceEvent(System.currentTimeMillis(),
meta.getClientIp(), service.getNamespace(), service.getGroup(), service.getName()));
}
return new SubscribeServiceResponse(ResponseCode.SUCCESS.getCode(), "success", serviceInfo);
}我们重点关注订阅服务的方法：
public void subscribeService(Service service, Subscriber subscriber, String clientId) {
Service singleton = ServiceManager.getInstance().getSingletonIfExist(service).orElse(service);
Client client = clientManager.getClient(clientId);
if (!clientIsLegal(client, clientId)) {
return;
}
// 添加到订阅者列表中，实际上就是保存在map中
// 订阅者列表： protected final ConcurrentHashMap subscribers = new ConcurrentHashMap<>(16, 0.75f, 1);
client.addServiceSubscriber(singleton, subscriber);
client.setLastUpdatedTime();
// 发布客户端订阅事件
NotifyCenter.publishEvent(new ClientOperationEvent.ClientSubscribeServiceEvent(singleton, clientId));
} 将service添加到订阅者列表中，然后发布客户端订阅事件，这个在之前分析过，客户端订阅事件是在com.alibaba.nacos.naming.core.v2.index.ClientServiceIndexesManager#handleClientOperation进行处理，
核心逻辑就是将服务添加到ClientServiceIndexesManager的subscriberIndexes订阅者列表中：
private final ConcurrentMap> subscriberIndexes = new ConcurrentHashMap<>(); 3.2.3、处理服务信息
public ServiceInfo processServiceInfo(ServiceInfo serviceInfo) {
String serviceKey = serviceInfo.getKey();
if (serviceKey == null) {
return null;
}
// 获取老的服务
ServiceInfo oldService = serviceInfoMap.get(serviceInfo.getKey());
if (isEmptyOrErrorPush(serviceInfo)) {
//empty or error push, just ignore
return oldService;
}
// 重新存入客户端缓存中
serviceInfoMap.put(serviceInfo.getKey(), serviceInfo);
// 对比下服务信息是否发生变更
boolean changed = isChangedServiceInfo(oldService, serviceInfo);
if (StringUtils.isBlank(serviceInfo.getJsonFromServer())) {
serviceInfo.setJsonFromServer(JacksonUtils.toJson(serviceInfo));
}
MetricsMonitor.getServiceInfoMapSizeMonitor().set(serviceInfoMap.size());
if (changed) {
NAMING_LOGGER.info("current ips:({}) service: {} -> {}", serviceInfo.ipCount(), serviceInfo.getKey(),
JacksonUtils.toJson(serviceInfo.getHosts()));
// 如果发生改变，发送实例变更事件，处理源码在：InstancesChangeNotifier
NotifyCenter.publishEvent(new InstancesChangeEvent(notifierEventScope, serviceInfo.getName(), serviceInfo.getGroupName(),
serviceInfo.getClusters(), serviceInfo.getHosts()));
// 同步serviceInfo数据到本地文件
DiskCache.write(serviceInfo, cacheDir);
}
return serviceInfo;
}3.3、非订阅模式，通过grpc发送ServiceQueryRequest服务查询请求
真正执行的是com.alibaba.nacos.client.naming.remote.NamingClientProxyDelegate#queryInstancesOfService()：
public ServiceInfo queryInstancesOfService(String serviceName, String groupName, String clusters, int udpPort,
boolean healthyOnly) throws NacosException {
return grpcClientProxy.queryInstancesOfService(serviceName, groupName, clusters, udpPort, healthyOnly);
}
public ServiceInfo queryInstancesOfService(String serviceName, String groupName, String clusters, int udpPort,
boolean healthyOnly) throws NacosException {
// 构建服务查询请求
// Nacos服务端处理是在：com.alibaba.nacos.naming.remote.rpc.handler.ServiceQueryRequestHandler.handle
ServiceQueryRequest request = new ServiceQueryRequest(namespaceId, serviceName, groupName);
request.setCluster(clusters);
request.setHealthyOnly(healthyOnly);
request.setUdpPort(udpPort);
// 通过grpc请求Nacos服务端处理
QueryServiceResponse response = requestToServer(request, QueryServiceResponse.class);
return response.getServiceInfo();
}queryInstancesOfService()核心就是构建了一个服务查询请求，通过grpc请求Nacos服务端，接下来我们直接看服务端的处理代码，具体是在：com.alibaba.nacos.naming.remote.rpc.handler.ServiceQueryRequestHandler#handle。
public QueryServiceResponse handle(ServiceQueryRequest request, RequestMeta meta) throws NacosException {
String namespaceId = request.getNamespace();
String groupName = request.getGroupName();
String serviceName = request.getServiceName();
Service service = Service.newService(namespaceId, groupName, serviceName);
String cluster = null == request.getCluster() ? "" : request.getCluster();
boolean healthyOnly = request.isHealthyOnly();
// 从缓存中获取serviceInfo
ServiceInfo result = serviceStorage.getData(service);
// 从内存(map)获取ServiceMetadata
ServiceMetadata serviceMetadata = metadataManager.getServiceMetadata(service).orElse(null);
// 获取有保护机制的健康实例
result = ServiceUtil.selectInstancesWithHealthyProtection(result, serviceMetadata, cluster, healthyOnly, true,
meta.getClientIp());
return QueryServiceResponse.buildSuccessResponse(result);
}3.4、筛选满足条件的实例
private List selectInstances(ServiceInfo serviceInfo, boolean healthy) {
List list;
if (serviceInfo == null || CollectionUtils.isEmpty(list = serviceInfo.getHosts())) {
return new ArrayList<>();
}
// 遍历所有实例，直接移除掉不满足条件的实例
Iterator iterator = list.iterator();
while (iterator.hasNext()) {
Instance instance = iterator.next();
// 筛选出健康、启用、权重大于0的实例
if (healthy != instance.isHealthy() || !instance.isEnabled() || instance.getWeight() <= 0) {
iterator.remove();
}
}
return list;
} 3.5、总结图