聊聊nacos的ServerListManager

序

本文主要研究一下nacos的ServerListManager

ServerListManager

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/cluster/ServerListManager.java

@Component("serverListManager")
public class ServerListManager {

    private static final int STABLE_PERIOD = 60 * 1000;

    @Autowired
    private SwitchDomain switchDomain;

    private List<ServerChangeListener> listeners = new ArrayList<>();

    private List<Server> servers = new ArrayList<>();

    private List<Server> healthyServers = new ArrayList<>();

    private Map<String, List<Server>> distroConfig = new ConcurrentHashMap<>();

    private Map<String, Long> distroBeats = new ConcurrentHashMap<>(16);

    private Set<String> liveSites = new HashSet<>();

    private final static String LOCALHOST_SITE = UtilsAndCommons.UNKNOWN_SITE;

    private long lastHealthServerMillis = 0L;

    private boolean autoDisabledHealthCheck = false;

    private Synchronizer synchronizer = new ServerStatusSynchronizer();

    public void listen(ServerChangeListener listener) {
        listeners.add(listener);
    }

    @PostConstruct
    public void init() {
        GlobalExecutor.registerServerListUpdater(new ServerListUpdater());
        GlobalExecutor.registerServerStatusReporter(new ServerStatusReporter(), 5000);
    }

    //......
}

• ServerListManager的init方法注册了ServerListUpdater、ServerStatusReporter两个定时任务

GlobalExecutor

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/misc/GlobalExecutor.java

public class GlobalExecutor {

    public static final long HEARTBEAT_INTERVAL_MS = TimeUnit.SECONDS.toMillis(5L);

    public static final long LEADER_TIMEOUT_MS = TimeUnit.SECONDS.toMillis(15L);

    public static final long RANDOM_MS = TimeUnit.SECONDS.toMillis(5L);

    public static final long TICK_PERIOD_MS = TimeUnit.MILLISECONDS.toMillis(500L);

    private static final long NACOS_SERVER_LIST_REFRESH_INTERVAL = TimeUnit.SECONDS.toMillis(5);

    private static final long PARTITION_DATA_TIMED_SYNC_INTERVAL = TimeUnit.SECONDS.toMillis(5);

    private static final long SERVER_STATUS_UPDATE_PERIOD = TimeUnit.SECONDS.toMillis(5);

    //......

    public static void registerServerListUpdater(Runnable runnable) {
        executorService.scheduleAtFixedRate(runnable, 0, NACOS_SERVER_LIST_REFRESH_INTERVAL, TimeUnit.MILLISECONDS);
    }

    public static void registerServerStatusReporter(Runnable runnable, long delay) {
        SERVER_STATUS_EXECUTOR.schedule(runnable, delay, TimeUnit.MILLISECONDS);
    }   
     
    //......
}

• registerServerListUpdater是每隔NACOS_SERVER_LIST_REFRESH_INTERVAL调度一次，默认是5秒；registerServerStatusReporter则是调度一个延时任务

ServerListUpdater

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/cluster/ServerListManager.java

public class ServerListUpdater implements Runnable {

        @Override
        public void run() {
            try {
                List<Server> refreshedServers = refreshServerList();
                List<Server> oldServers = servers;

                if (CollectionUtils.isEmpty(refreshedServers)) {
                    Loggers.RAFT.warn("refresh server list failed, ignore it.");
                    return;
                }

                boolean changed = false;

                List<Server> newServers = (List<Server>) CollectionUtils.subtract(refreshedServers, oldServers);
                if (CollectionUtils.isNotEmpty(newServers)) {
                    servers.addAll(newServers);
                    changed = true;
                    Loggers.RAFT.info("server list is updated, new: {} servers: {}", newServers.size(), newServers);
                }

                List<Server> deadServers = (List<Server>) CollectionUtils.subtract(oldServers, refreshedServers);
                if (CollectionUtils.isNotEmpty(deadServers)) {
                    servers.removeAll(deadServers);
                    changed = true;
                    Loggers.RAFT.info("server list is updated, dead: {}, servers: {}", deadServers.size(), deadServers);
                }

                if (changed) {
                    notifyListeners();
                }

            } catch (Exception e) {
                Loggers.RAFT.info("error while updating server list.", e);
            }
        }
    }

    private List<Server> refreshServerList() {

        List<Server> result = new ArrayList<>();

        if (STANDALONE_MODE) {
            Server server = new Server();
            server.setIp(NetUtils.getLocalAddress());
            server.setServePort(RunningConfig.getServerPort());
            result.add(server);
            return result;
        }

        List<String> serverList = new ArrayList<>();
        try {
            serverList = readClusterConf();
        } catch (Exception e) {
            Loggers.SRV_LOG.warn("failed to get config: " + CLUSTER_CONF_FILE_PATH, e);
        }

        if (Loggers.SRV_LOG.isDebugEnabled()) {
            Loggers.SRV_LOG.debug("SERVER-LIST from cluster.conf: {}", result);
        }

        //use system env
        if (CollectionUtils.isEmpty(serverList)) {
            serverList = SystemUtils.getIPsBySystemEnv(UtilsAndCommons.SELF_SERVICE_CLUSTER_ENV);
            if (Loggers.SRV_LOG.isDebugEnabled()) {
                Loggers.SRV_LOG.debug("SERVER-LIST from system variable: {}", result);
            }
        }

        if (CollectionUtils.isNotEmpty(serverList)) {

            for (int i = 0; i < serverList.size(); i++) {

                String ip;
                int port;
                String server = serverList.get(i);
                if (server.contains(UtilsAndCommons.IP_PORT_SPLITER)) {
                    ip = server.split(UtilsAndCommons.IP_PORT_SPLITER)[0];
                    port = Integer.parseInt(server.split(UtilsAndCommons.IP_PORT_SPLITER)[1]);
                } else {
                    ip = server;
                    port = RunningConfig.getServerPort();
                }

                Server member = new Server();
                member.setIp(ip);
                member.setServePort(port);
                result.add(member);
            }
        }

        return result;
    }

    private void notifyListeners() {

        GlobalExecutor.notifyServerListChange(new Runnable() {
            @Override
            public void run() {
                for (ServerChangeListener listener : listeners) {
                    listener.onChangeServerList(servers);
                    listener.onChangeHealthyServerList(healthyServers);
                }
            }
        });
    }

• ServerListUpdater实现了Runnable接口，其run方法会通过refreshServerList方法从配置文件读取最新的servers配置，然后对比oldServers，看哪些是新增，哪些是删除的，如果确实有变更则通过notifyListeners方法进行通知回调ServerChangeListener的onChangeServerList、onChangeHealthyServerList方法

ServerStatusReporter

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/cluster/ServerListManager.java

private class ServerStatusReporter implements Runnable {

        @Override
        public void run() {
            try {

                if (RunningConfig.getServerPort() <= 0) {
                    return;
                }

                checkDistroHeartbeat();

                int weight = Runtime.getRuntime().availableProcessors() / 2;
                if (weight <= 0) {
                    weight = 1;
                }

                long curTime = System.currentTimeMillis();
                String status = LOCALHOST_SITE + "#" + NetUtils.localServer() + "#" + curTime + "#" + weight + "/r/n";

                //send status to itself
                onReceiveServerStatus(status);

                List<Server> allServers = getServers();

                if (!contains(NetUtils.localServer())) {
                    Loggers.SRV_LOG.error("local ip is not in serverlist, ip: {}, serverlist: {}", NetUtils.localServer(), allServers);
                    return;
                }

                if (allServers.size() > 0 && !NetUtils.localServer().contains(UtilsAndCommons.LOCAL_HOST_IP)) {
                    for (com.alibaba.nacos.naming.cluster.servers.Server server : allServers) {
                        if (server.getKey().equals(NetUtils.localServer())) {
                            continue;
                        }

                        Message msg = new Message();
                        msg.setData(status);

                        synchronizer.send(server.getKey(), msg);

                    }
                }
            } catch (Exception e) {
                Loggers.SRV_LOG.error("[SERVER-STATUS] Exception while sending server status", e);
            } finally {
                GlobalExecutor.registerServerStatusReporter(this, switchDomain.getServerStatusSynchronizationPeriodMillis());
            }

        }
    }

• ServerStatusReporter实现了Runnable接口，其run方法首先执行checkDistroHeartbeat，然后执行onReceiveServerStatus，最后获取servers列表通知通过synchronizer.send(server.getKey(), msg)方法通知其他server自己的状态；最后再次通过registerServerStatusReporter调度下次执行的时间

checkDistroHeartbeat

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/cluster/ServerListManager.java

private void checkDistroHeartbeat() {

        Loggers.SRV_LOG.debug("check distro heartbeat.");

        List<Server> servers = distroConfig.get(LOCALHOST_SITE);
        if (CollectionUtils.isEmpty(servers)) {
            return;
        }

        List<Server> newHealthyList = new ArrayList<>(servers.size());
        long now = System.currentTimeMillis();
        for (Server s: servers) {
            Long lastBeat = distroBeats.get(s.getKey());
            if (null == lastBeat) {
                continue;
            }
            s.setAlive(now - lastBeat < switchDomain.getDistroServerExpiredMillis());
        }

        //local site servers
        List<String> allLocalSiteSrvs = new ArrayList<>();
        for (Server server : servers) {

            if (server.getKey().endsWith(":0")) {
                continue;
            }

            server.setAdWeight(switchDomain.getAdWeight(server.getKey()) == null ? 0 : switchDomain.getAdWeight(server.getKey()));

            for (int i = 0; i < server.getWeight() + server.getAdWeight(); i++) {

                if (!allLocalSiteSrvs.contains(server.getKey())) {
                    allLocalSiteSrvs.add(server.getKey());
                }

                if (server.isAlive() && !newHealthyList.contains(server)) {
                    newHealthyList.add(server);
                }
            }
        }

        Collections.sort(newHealthyList);
        float curRatio = (float) newHealthyList.size() / allLocalSiteSrvs.size();

        if (autoDisabledHealthCheck
            && curRatio > switchDomain.getDistroThreshold()
            && System.currentTimeMillis() - lastHealthServerMillis > STABLE_PERIOD) {
            Loggers.SRV_LOG.info("[NACOS-DISTRO] distro threshold restored and " +
                "stable now, enable health check. current ratio: {}", curRatio);

            switchDomain.setHealthCheckEnabled(true);

            // we must set this variable, otherwise it will conflict with user's action
            autoDisabledHealthCheck = false;
        }

        if (!CollectionUtils.isEqualCollection(healthyServers, newHealthyList)) {
            // for every change disable healthy check for some while
            if (switchDomain.isHealthCheckEnabled()) {
                Loggers.SRV_LOG.info("[NACOS-DISTRO] healthy server list changed, " +
                        "disable health check for {} ms from now on, old: {}, new: {}", STABLE_PERIOD,
                    healthyServers, newHealthyList);

                switchDomain.setHealthCheckEnabled(false);
                autoDisabledHealthCheck = true;

                lastHealthServerMillis = System.currentTimeMillis();
            }

            healthyServers = newHealthyList;
            notifyListeners();
        }
    }

• checkDistroHeartbeat方法会遍历servers从distroBeats获取lastBeat信息，然后判断距离lastBeat的时间是否小于distroServerExpiredMillis，小于则alive为true，否则alive为false；之后遍历servers更新adWeight
• 然后计算curRatio，如果大于distroThreshold且autoDisabledHealthCheck为true且距离lastHealthServerMillis大于STABLE_PERIOD则会执行switchDomain.setHealthCheckEnabled(true)并更新autoDisabledHealthCheck为false
• 最后判断healthyServers与newHealthyList是否一致，不一致且switchDomain.isHealthCheckEnabled()则会执行switchDomain.setHealthCheckEnabled(false)且设置autoDisabledHealthCheck为true，更新lastHealthServerMillis；最后更新healthyServers，执行notifyListeners方法

小结

• ServerListManager的init方法注册了ServerListUpdater、ServerStatusReporter两个定时任务
• ServerListUpdater实现了Runnable接口，其run方法会通过refreshServerList方法从配置文件读取最新的servers配置，然后对比oldServers，看哪些是新增，哪些是删除的，如果确实有变更则通过notifyListeners方法进行通知回调ServerChangeListener的onChangeServerList、onChangeHealthyServerList方法
• ServerStatusReporter实现了Runnable接口，其run方法首先执行checkDistroHeartbeat，然后执行onReceiveServerStatus，最后获取servers列表通知通过synchronizer.send(server.getKey(), msg)方法通知其他server自己的状态；最后再次通过registerServerStatusReporter调度下次执行的时间

doc

• ServerListManager