Nacos注册中心6-Client端（获取调用服务的提供者列表）

今天药忘吃喽~ 2023-10-03 21:15 13阅读 0赞

## 0. 环境 ##

*  nacos版本：1.4.1
 *  Spring Cloud : 2020.0.2
 *  Spring Boot ：2.4.4
 *  Spring Cloud alibaba: 2.2.5.RELEASE

测试代码：[github.com/hsfxuebao/s…][github.com_hsfxuebao_s]

## 1. 获取调用服务的提供者列表 ##

请求时机：Client端在调用服务提供者具体方法时，才能调用

public ZoneAwareLoadBalancer(IClientConfig clientConfig, IRule rule,
                                 IPing ping, ServerList<T> serverList, ServerListFilter<T> filter,
                                 ServerListUpdater serverListUpdater) {
        super(clientConfig, rule, ping, serverList, filter, serverListUpdater);
    }
    
    public DynamicServerListLoadBalancer(IClientConfig clientConfig, IRule rule, IPing ping,
                                         ServerList<T> serverList, ServerListFilter<T> filter,
                                         ServerListUpdater serverListUpdater) {
        super(clientConfig, rule, ping);
        this.serverListImpl = serverList;
        this.filter = filter;
        this.serverListUpdater = serverListUpdater;
        if (filter instanceof AbstractServerListFilter) {
            ((AbstractServerListFilter) filter).setLoadBalancerStats(getLoadBalancerStats());
        }
        restOfInit(clientConfig);
    }
    
    void restOfInit(IClientConfig clientConfig) {
        boolean primeConnection = this.isEnablePrimingConnections();
        // turn this off to avoid duplicated asynchronous priming done in BaseLoadBalancer.setServerList()
        this.setEnablePrimingConnections(false);
        enableAndInitLearnNewServersFeature();
    
        updateListOfServers();
        if (primeConnection && this.getPrimeConnections() != null) {
            this.getPrimeConnections()
                    .primeConnections(getReachableServers());
        }
        this.setEnablePrimingConnections(primeConnection);
        LOGGER.info("DynamicServerListLoadBalancer for client {} initialized: {}", clientConfig.getClientName(), this.toString());
    }
    com.netflix.loadbalancer.DynamicServerListLoadBalancer#updateListOfServers
    @VisibleForTesting
    public void updateListOfServers() {
        List<T> servers = new ArrayList<T>();
        if (serverListImpl != null) {
            servers = serverListImpl.getUpdatedListOfServers();
            LOGGER.debug("List of Servers for {} obtained from Discovery client: {}",
                    getIdentifier(), servers);
    
            if (filter != null) {
                servers = filter.getFilteredListOfServers(servers);
                LOGGER.debug("Filtered List of Servers for {} obtained from Discovery client: {}",
                        getIdentifier(), servers);
            }
        }
        updateAllServerList(servers);
    }
    
    com.alibaba.cloud.nacos.ribbon.NacosServerList#getUpdatedListOfServers
    @Override
    public List<NacosServer> getUpdatedListOfServers() {
       return getServers();
    }
    private List<NacosServer> getServers() {
       try {
          String group = discoveryProperties.getGroup();
          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);
       }
    }
    复制代码

com.alibaba.nacos.client.naming.NacosNamingService\#selectInstances:

@Override
    public List<Instance> selectInstances(String serviceName, String groupName, List<String> clusters, boolean healthy,
            boolean subscribe) throws NacosException {
    
        ServiceInfo serviceInfo;
        if (subscribe) {
            // 获取到要调用服务的serviceInfo
            serviceInfo = hostReactor.getServiceInfo(NamingUtils.getGroupedName(serviceName, groupName),
                    StringUtils.join(clusters, ","));
        } else {
            serviceInfo = hostReactor
                    .getServiceInfoDirectlyFromServer(NamingUtils.getGroupedName(serviceName, groupName),
                            StringUtils.join(clusters, ","));
        }
        // todo 从serviceInfo的所有instance实例中过滤出所有可用的
        return selectInstances(serviceInfo, healthy);
    }
    复制代码

其中 `getServiceInfo`方法上一篇[Nacos注册中心5-Client端(更新本地服务)][Nacos_5-Client]中已经信息分析了，我们看一下`selectInstances(serviceInfo, healthy)`：

private List<Instance> selectInstances(ServiceInfo serviceInfo, boolean healthy) {
        List<Instance> list;
        if (serviceInfo == null || CollectionUtils.isEmpty(list = serviceInfo.getHosts())) {
            return new ArrayList<Instance>();
        }
    
        Iterator<Instance> iterator = list.iterator();
        // 迭代服务的所有instance实例
        while (iterator.hasNext()) {
            Instance instance = iterator.next();
            // 若当前instance不是健康的，或不可用，或其权重小于等于0，则从列表中将其删除
            if (healthy != instance.isHealthy() || !instance.isEnabled() || instance.getWeight() <= 0) {
                iterator.remove();
            }
        }
        // 返回的这个列表中包含的instance都是可用的
        return list;
    }
    复制代码

## 2. 方法调用图 ##

## 参考文章 ##

[nacos-1.4.1源码分析（注释）][nacos-1.4.1]  
[springcloud-source-study学习github地址][github.com_hsfxuebao_s]  
[深度解析nacos注册中心][nacos]  
[mac系统如何安装nacos][mac_nacos]

[github.com_hsfxuebao_s]: https://link.juejin.cn?target=https%3A%2F%2Fgithub.com%2Fhsfxuebao%2Fspringcloud-source-study
[Nacos_5-Client]: https://juejin.cn/post/7160859202112454692
[nacos-1.4.1]: https://link.juejin.cn?target=https%3A%2F%2Fgithub.com%2Fhsfxuebao%2Fnacos-1.4.1-source
[nacos]: https://link.juejin.cn?target=https%3A%2F%2Fblog.csdn.net%2Fyuanshangshenghuo%2Fcategory_10666735.html
[mac_nacos]: https://link.juejin.cn?target=https%3A%2F%2Fblog.csdn.net%2Fgongzi_9%2Farticle%2Fdetails%2F123359171