服务端解决实例列表申请的入口是InstanceController#list。
InstanceController#list
public ObjectNode list(HttpServletRequest request) throws Exception { // 其余略 // 获取服务列表 return doSrvIpxt(namespaceId, serviceName, agent, clusters, clientIP, udpPort, env, isCheck, app, tenant, healthyOnly);}InstanceController#doSrvIpxt
这里次要是推送UDP申请，退出Client，Nacos - 服务端解决心跳申请的clients就是这里退出的。
另外就是判断爱护阈值，如果比例低于阈值，则把衰弱和不衰弱的都返回，如果高于阈值，就只返回衰弱的实例。
public ObjectNode doSrvIpxt(String namespaceId, String serviceName, String agent, String clusters, String clientIP, int udpPort, String env, boolean isCheck, String app, String tid, boolean healthyOnly) throws Exception { ClientInfo clientInfo = new ClientInfo(agent); ObjectNode result = JacksonUtils.createEmptyJsonNode(); // 从serviceMap缓存获取Service Service service = serviceManager.getService(namespaceId, serviceName); long cacheMillis = switchDomain.getDefaultCacheMillis(); // now try to enable the push try { // 端口大于0，且客户端agent信息合乎则发表 if (udpPort > 0 && pushService.canEnablePush(agent)) { // 心跳那个章节的client就是这里加的 pushService .addClient(namespaceId, serviceName, clusters, agent, new InetSocketAddress(clientIP, udpPort), pushDataSource, tid, app); cacheMillis = switchDomain.getPushCacheMillis(serviceName); } } catch (Exception e) { Loggers.SRV_LOG .error("[NACOS-API] failed to added push client {}, {}:{}", clientInfo, clientIP, udpPort, e); cacheMillis = switchDomain.getDefaultCacheMillis(); } // 为空封装返回 if (service == null) { if (Loggers.SRV_LOG.isDebugEnabled()) { Loggers.SRV_LOG.debug("no instance to serve for service: {}", serviceName); } result.put("name", serviceName); result.put("clusters", clusters); result.put("cacheMillis", cacheMillis); result.replace("hosts", JacksonUtils.createEmptyArrayNode()); return result; } // 查看service状态 checkIfDisabled(service); List<Instance> srvedIPs; // 获取相干实例的ip srvedIPs = service.srvIPs(Arrays.asList(StringUtils.split(clusters, ","))); // filter ips using selector: // 对ip过滤 if (service.getSelector() != null && StringUtils.isNotBlank(clientIP)) { srvedIPs = service.getSelector().select(clientIP, srvedIPs); } // id为空封装返回 if (CollectionUtils.isEmpty(srvedIPs)) { if (Loggers.SRV_LOG.isDebugEnabled()) { Loggers.SRV_LOG.debug("no instance to serve for service: {}", serviceName); } if (clientInfo.type == ClientInfo.ClientType.JAVA && clientInfo.version.compareTo(VersionUtil.parseVersion("1.0.0")) >= 0) { result.put("dom", serviceName); } else { result.put("dom", NamingUtils.getServiceName(serviceName)); } result.put("name", serviceName); result.put("cacheMillis", cacheMillis); result.put("lastRefTime", System.currentTimeMillis()); result.put("checksum", service.getChecksum()); result.put("useSpecifiedURL", false); result.put("clusters", clusters); result.put("env", env); result.set("hosts", JacksonUtils.createEmptyArrayNode()); result.set("metadata", JacksonUtils.transferToJsonNode(service.getMetadata())); return result; } // 次要是把衰弱和不衰弱的辨别进去 Map<Boolean, List<Instance>> ipMap = new HashMap<>(2); ipMap.put(Boolean.TRUE, new ArrayList<>()); ipMap.put(Boolean.FALSE, new ArrayList<>()); for (Instance ip : srvedIPs) { ipMap.get(ip.isHealthy()).add(ip); } if (isCheck) { result.put("reachProtectThreshold", false); } double threshold = service.getProtectThreshold(); // 阈值爱护，衰弱实例和吧衰弱实例的比例小于阈值，则把衰弱和不衰弱的都返回 if ((float) ipMap.get(Boolean.TRUE).size() / srvedIPs.size() <= threshold) { Loggers.SRV_LOG.warn("protect threshold reached, return all ips, service: {}", serviceName); if (isCheck) { result.put("reachProtectThreshold", true); } ipMap.get(Boolean.TRUE).addAll(ipMap.get(Boolean.FALSE)); ipMap.get(Boolean.FALSE).clear(); } // 其余略，就是解决ipMap的信息返回值 return result;}总结
流程图如下：