Nacos - 服务端处理实例列表请求

服务端处理实例列表请求的入口是InstanceController#list。

InstanceController#list

public ObjectNode list(HttpServletRequest request) throws Exception {
        
    // 其他略
    // 获取服务列表
    return doSrvIpxt(namespaceId, serviceName, agent, clusters, clientIP, udpPort, env, isCheck, app, tenant,
            healthyOnly);
}

InstanceController#doSrvIpxt

这里主要是推送UDP请求，加入Client，Nacos - 服务端处理心跳请求的clients就是这里加入的。
另外就是判断保护阈值，如果比例低于阈值，则把健康和不健康的都返回，如果高于阈值，就只返回健康的实例。

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信息符合则发表
        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;
    }
    // 检查service状态
    checkIfDisabled(service);
    
    List<Instance> srvedIPs;
    // 获取相关实例的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;
    }
    // 主要是把健康和不健康的区分出来
    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();
    // 阈值保护，健康实例和吧健康实例的比例小于阈值，则把健康和不健康的都返回
    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();
    }
    
    // 其他略，就是处理ipMap的信息返回值
    return result;
}

流程图如下：