nacos1.4源码-服务发现、心跳机制

nacos的服务发现主要采用服务端主动推送+客户端定时拉取；心跳机制通过每5s向服务端发送心跳任务来保活，当超过15s服务端未接收到心跳任务时，将该实例设置为非健康状态；当超过30s时，删除该实例。

1.服务发现

nacos主要采用服务端主动推送+客户端定时拉取来保证AP架构的高可用性。

NacosNamingService：服务发现的接口（客户端！）

每个nacos实例有本地缓存Map，存放所有的实例

调用查询服务实例列表

/nacos`/v1/ns/instance/list

NacosNamingService.getAllInstances() -> getServiceInfo()

核心方法是getServiceInfo，代码如下：

java 复制代码

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);// 从本地拿实例
        
        if (null == serviceObj) {// 如果拿到为空，则更新服务列表
            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);// 定时拉取
        
        return serviceInfoMap.get(serviceObj.getKey());// 从map拿
    }

本地从服务端拉取服务实例，放到本地缓存中

java 复制代码

public String queryList(String serviceName, String clusters, int udpPort, boolean healthyOnly)
            throws NacosException {
        
        final Map<String, String> params = new HashMap<String, String>(8);
        params.put(CommonParams.NAMESPACE_ID, namespaceId);
        params.put(CommonParams.SERVICE_NAME, serviceName);
        params.put("clusters", clusters);
        params.put("udpPort", String.valueOf(udpPort));
        params.put("clientIP", NetUtils.localIP());
        params.put("healthyOnly", String.valueOf(healthyOnly));
        
        return reqApi(UtilAndComs.nacosUrlBase + "/instance/list", params, HttpMethod.GET);// 调用接口
    }

客户端通过定时任务-->定时拉取服务端的实例，更新本地缓存（在发起服务调用的时候，才会执行定时任务！）

java 复制代码

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);
        }
    }

2.心跳机制

NamingService->register

注册实例的时候，客户端会有一个心跳任务，定时5s向服务端发送心跳！

executorService.schedule(new BeatTask(beatInfo), beatInfo.getPeriod(), TimeUnit.MILLISECONDS);

BeatTask就是心跳任务

调用Instance/beat接口，发送实例心跳检查

BeatTask#run的代码如下：

java 复制代码

 @Override
        public void run() {
            if (beatInfo.isStopped()) {
                return;
            }
            long nextTime = beatInfo.getPeriod();
            try {
                JsonNode result = serverProxy.sendBeat(beatInfo, BeatReactor.this.lightBeatEnabled);
                long interval = result.get("clientBeatInterval").asLong();
                boolean lightBeatEnabled = false;
                if (result.has(CommonParams.LIGHT_BEAT_ENABLED)) {
                    lightBeatEnabled = result.get(CommonParams.LIGHT_BEAT_ENABLED).asBoolean();
                }
                BeatReactor.this.lightBeatEnabled = lightBeatEnabled;
                if (interval > 0) {
                    nextTime = interval;
                }
                int code = NamingResponseCode.OK;
                if (result.has(CommonParams.CODE)) {
                    code = result.get(CommonParams.CODE).asInt();
                }
                if (code == NamingResponseCode.RESOURCE_NOT_FOUND) {
                    Instance instance = new Instance();
                    instance.setPort(beatInfo.getPort());
                    instance.setIp(beatInfo.getIp());
                    instance.setWeight(beatInfo.getWeight());
                    instance.setMetadata(beatInfo.getMetadata());
                    instance.setClusterName(beatInfo.getCluster());
                    instance.setServiceName(beatInfo.getServiceName());
                    instance.setInstanceId(instance.getInstanceId());
                    instance.setEphemeral(true);
                    try {
                        serverProxy.registerService(beatInfo.getServiceName(),
                                NamingUtils.getGroupName(beatInfo.getServiceName()), instance);
                    } catch (Exception ignore) {
                    }
                }
            } catch (NacosException ex) {
                NAMING_LOGGER.warn("[CLIENT-BEAT] failed to send beat: {}, code: {}, msg: {}",
                        JacksonUtils.toJson(beatInfo), ex.getErrCode(), ex.getErrMsg());
    
            } catch (Exception unknownEx) {
                NAMING_LOGGER.error("[CLIENT-BEAT] failed to send beat: {}, unknown exception msg: {}",
                        JacksonUtils.toJson(beatInfo), unknownEx.getMessage(), unknownEx);
            } finally {
                executorService.schedule(new BeatTask(beatInfo), nextTime, TimeUnit.MILLISECONDS);// 定时任务
            }
        }

服务端会更新心跳的时间！每隔5秒检查一下实例健康状态

对于集群而言，在一台服务端执行定时任务即可！不需要再所有节点都执行定时任务

当实例下线后，服务端通过InstanceController，检查健康状态（健康任务检查）。代码入口：

createEmptyService->createServiceIfAbsent->putServiceAndInit->init->scheduleCheck（定时任务）

if (System.currentTimeMillis() - instance.getLastBeat() > instance.getInstanceHeartBeatTimeOut()) {// 心跳时间判断

如果超过15秒，设置实例为非健康（更新健康状态）

if (System.currentTimeMillis() - instance.getLastBeat() > instance.getIpDeleteTimeout()) {// 如果已经过去了30s，直接删掉这个机器（删除实例）

asyncHttpRequest(url, headers, paramValues, callback, HttpMethod.DELETE);

核心代码如下：

java 复制代码

@Override
    public void run() {
        try {
            if (!getDistroMapper().responsible(service.getName())) {
                return;
            }
            
            if (!getSwitchDomain().isHealthCheckEnabled()) {
                return;
            }
            
            List<Instance> instances = service.allIPs(true);// 获取服务端的所有实例
            
            // first set health status of instances:
            for (Instance instance : instances) {
                if (System.currentTimeMillis() - instance.getLastBeat() > instance.getInstanceHeartBeatTimeOut()) {// 心跳时间判断
                    if (!instance.isMarked()) {
                        if (instance.isHealthy()) {
                            instance.setHealthy(false);// 如果超过15s，健康设置为false
                            Loggers.EVT_LOG
                                    .info("{POS} {IP-DISABLED} valid: {}:{}@{}@{}, region: {}, msg: client timeout after {}, last beat: {}",
                                            instance.getIp(), instance.getPort(), instance.getClusterName(),
                                            service.getName(), UtilsAndCommons.LOCALHOST_SITE,
                                            instance.getInstanceHeartBeatTimeOut(), instance.getLastBeat());
                            getPushService().serviceChanged(service);
                            ApplicationUtils.publishEvent(new InstanceHeartbeatTimeoutEvent(this, instance));
                        }
                    }
                }
            }
            
            if (!getGlobalConfig().isExpireInstance()) {
                return;
            }
            
            // then remove obsolete instances:
            for (Instance instance : instances) {
                
                if (instance.isMarked()) {
                    continue;
                }
                
                if (System.currentTimeMillis() - instance.getLastBeat() > instance.getIpDeleteTimeout()) {
                    // delete instance
                    Loggers.SRV_LOG.info("[AUTO-DELETE-IP] service: {}, ip: {}", service.getName(),
                            JacksonUtils.toJson(instance));
                    deleteIp(instance);
                }
            }
            
        } catch (Exception e) {
            Loggers.SRV_LOG.warn("Exception while processing client beat time out.", e);
        }
        
    }

3.服务事件变动

客户端每隔5秒从服务端拉取一次信息，是不是有延迟！

对于AP架构而言，有一点延迟无所谓。Ribbon会进行重试

当服务端的服务列表变化时，服务端会主动推送给客户端信息

核心代码入口：notifier#run->handle->onChange

onChange更新注册表的相关代码！

getPushService().serviceChanged(this);// 发布服务变化的事件，通知客户端

java 复制代码

public void updateIPs(Collection<Instance> instances, boolean ephemeral) {
        Map<String, List<Instance>> ipMap = new HashMap<>(clusterMap.size());
        for (String clusterName : clusterMap.keySet()) {
            ipMap.put(clusterName, new ArrayList<>());
        }
        
        for (Instance instance : instances) {
            try {
                if (instance == null) {
                    Loggers.SRV_LOG.error("[NACOS-DOM] received malformed ip: null");
                    continue;
                }
                
                if (StringUtils.isEmpty(instance.getClusterName())) {
                    instance.setClusterName(UtilsAndCommons.DEFAULT_CLUSTER_NAME);
                }
                
                if (!clusterMap.containsKey(instance.getClusterName())) {
                    Loggers.SRV_LOG
                            .warn("cluster: {} not found, ip: {}, will create new cluster with default configuration.",
                                    instance.getClusterName(), instance.toJson());
                    Cluster cluster = new Cluster(instance.getClusterName(), this);
                    cluster.init();
                    getClusterMap().put(instance.getClusterName(), cluster);
                }
                
                List<Instance> clusterIPs = ipMap.get(instance.getClusterName());
                if (clusterIPs == null) {
                    clusterIPs = new LinkedList<>();
                    ipMap.put(instance.getClusterName(), clusterIPs);
                }
                
                clusterIPs.add(instance);
            } catch (Exception e) {
                Loggers.SRV_LOG.error("[NACOS-DOM] failed to process ip: " + instance, e);
            }
        }
        
        for (Map.Entry<String, List<Instance>> entry : ipMap.entrySet()) {
            //make every ip mine
            List<Instance> entryIPs = entry.getValue();
            clusterMap.get(entry.getKey()).updateIps(entryIPs, ephemeral);// 核心注册逻辑
        }
        
        setLastModifiedMillis(System.currentTimeMillis());
        getPushService().serviceChanged(this);// 发布 服务变化 的事件
        StringBuilder stringBuilder = new StringBuilder();
        
        for (Instance instance : allIPs()) {
            stringBuilder.append(instance.toIpAddr()).append("_").append(instance.isHealthy()).append(",");
        }
        
        Loggers.EVT_LOG.info("[IP-UPDATED] namespace: {}, service: {}, ips: {}", getNamespaceId(), getName(),
                stringBuilder.toString());
        
    }

（通过全文搜索事件，找到这个方法）PushService#onApplicationEvent，它来处理事件。代码如下：

udpPush(ackEntry);// 服务端给客户端发送udp信息，通知客户端实例变动

java 复制代码

@Override
public void onApplicationEvent(ServiceChangeEvent event) {
    Service service = event.getService();
    String serviceName = service.getName();
    String namespaceId = service.getNamespaceId();
    
    Future future = GlobalExecutor.scheduleUdpSender(() -> {
    try {
        Loggers.PUSH.info(serviceName + " is changed, add it to push queue.");
        ConcurrentMap<String, PushClient> clients = clientMap
        .get(UtilsAndCommons.assembleFullServiceName(namespaceId, serviceName));
        if (MapUtils.isEmpty(clients)) {
            return;
        }

        Map<String, Object> cache = new HashMap<>(16);
        long lastRefTime = System.nanoTime();
        for (PushClient client : clients.values()) {
            if (client.zombie()) {
                Loggers.PUSH.debug("client is zombie: " + client.toString());
                clients.remove(client.toString());
                Loggers.PUSH.debug("client is zombie: " + client.toString());
                continue;
            }

            Receiver.AckEntry ackEntry;
            Loggers.PUSH.debug("push serviceName: {} to client: {}", serviceName, client.toString());
            String key = getPushCacheKey(serviceName, client.getIp(), client.getAgent());
            byte[] compressData = null;
            Map<String, Object> data = null;
            if (switchDomain.getDefaultPushCacheMillis() >= 20000 && cache.containsKey(key)) {
                org.javatuples.Pair pair = (org.javatuples.Pair) cache.get(key);
                compressData = (byte[]) (pair.getValue0());
                data = (Map<String, Object>) pair.getValue1();

                Loggers.PUSH.debug("[PUSH-CACHE] cache hit: {}:{}", serviceName, client.getAddrStr());
            }

            if (compressData != null) {
                ackEntry = prepareAckEntry(client, compressData, data, lastRefTime);
            } else {
                ackEntry = prepareAckEntry(client, prepareHostsData(client), lastRefTime);
                if (ackEntry != null) {
                    cache.put(key, new org.javatuples.Pair<>(ackEntry.origin.getData(), ackEntry.data));
                }
            }

            Loggers.PUSH.info("serviceName: {} changed, schedule push for: {}, agent: {}, key: {}",
                              client.getServiceName(), client.getAddrStr(), client.getAgent(),
                              (ackEntry == null ? null : ackEntry.key));

            udpPush(ackEntry);// 给客户端发送udp信息
        }
    } catch (Exception e) {
        Loggers.PUSH.error("[NACOS-PUSH] failed to push serviceName: {} to client, error: {}", serviceName, e);

    } finally {
        futureMap.remove(UtilsAndCommons.assembleFullServiceName(namespaceId, serviceName));
        }
        
    }, 1000, TimeUnit.MILLISECONDS);
    
    futureMap.put(UtilsAndCommons.assembleFullServiceName(namespaceId, serviceName), future);
    
}

客户端接收udp报文的代码如下：

java 复制代码

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);// 从本地拿实例

    if (null == serviceObj) {// 如果拿到为空，则更新服务列表
        serviceObj = new ServiceInfo(serviceName, clusters);

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

        updatingMap.put(serviceName, new Object());
        updateServiceNow(serviceName, clusters);// upd的端口