NacosNamingService中selectInstances的原理和作用

本篇内容主要讲解“NacosNamingService中selectInstances的原理和作用”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“NacosNamingService中selectInstances的原理和作用”吧!

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序

本文主要研究一下NacosNamingService的selectInstances

NacosNamingService

nacos-1.1.3/client/src/main/java/com/alibaba/nacos/client/naming/NacosNamingService.java

public class NacosNamingService implements NamingService {
    private static final String DEFAULT_PORT = "8080";
    private static final long DEFAULT_HEART_BEAT_INTERVAL = TimeUnit.SECONDS.toMillis(5);

    /**
     * Each Naming instance should have different namespace.
     */
    private String namespace;

    private String endpoint;

    private String serverList;

    private String cacheDir;

    private String logName;

    private HostReactor hostReactor;

    private BeatReactor beatReactor;

    private EventDispatcher eventDispatcher;

    private NamingProxy serverProxy;

    //......

    @Override
    public List selectInstances(String serviceName, boolean healthy) throws NacosException {
        return selectInstances(serviceName, new ArrayList(), healthy);
    }

    @Override
    public List selectInstances(String serviceName, String groupName, boolean healthy) throws NacosException {
        return selectInstances(serviceName, groupName, healthy, true);
    }

    @Override
    public List selectInstances(String serviceName, boolean healthy, boolean subscribe)
        throws NacosException {
        return selectInstances(serviceName, new ArrayList(), healthy, subscribe);
    }

    @Override
    public List selectInstances(String serviceName, String groupName, boolean healthy, boolean subscribe) throws NacosException {
        return selectInstances(serviceName, groupName, new ArrayList(), healthy, subscribe);
    }

    @Override
    public List selectInstances(String serviceName, List clusters, boolean healthy)
        throws NacosException {
        return selectInstances(serviceName, clusters, healthy, true);
    }

    @Override
    public List selectInstances(String serviceName, String groupName, List clusters, boolean healthy) throws NacosException {
        return selectInstances(serviceName, groupName, clusters, healthy, true);
    }

    @Override
    public List selectInstances(String serviceName, List clusters, boolean healthy,
                                          boolean subscribe) throws NacosException {
        return selectInstances(serviceName, Constants.DEFAULT_GROUP, clusters, healthy, subscribe);
    }

    @Override
    public List selectInstances(String serviceName, String groupName, List clusters, boolean healthy, boolean subscribe) throws NacosException {

        ServiceInfo serviceInfo;
        if (subscribe) {
            serviceInfo = hostReactor.getServiceInfo(NamingUtils.getGroupedName(serviceName, groupName), StringUtils.join(clusters, ","));
        } else {
            serviceInfo = hostReactor.getServiceInfoDirectlyFromServer(NamingUtils.getGroupedName(serviceName, groupName), StringUtils.join(clusters, ","));
        }
        return selectInstances(serviceInfo, healthy);
    }

    private List selectInstances(ServiceInfo serviceInfo, boolean healthy) {
        List list;
        if (serviceInfo == null || CollectionUtils.isEmpty(list = serviceInfo.getHosts())) {
            return new ArrayList();
        }

        Iterator iterator = list.iterator();
        while (iterator.hasNext()) {
            Instance instance = iterator.next();
            if (healthy != instance.isHealthy() || !instance.isEnabled() || instance.getWeight() <= 0) {
                iterator.remove();
            }
        }

        return list;
    }

    //......
}

selectInstances首先从hostReactor获取serviceInfo，然后再从serviceInfo.getHosts()剔除非healty、非enabled、weight小于等于0的instance再返回；如果subscribe为true，则执行hostReactor.getServiceInfo获取serviceInfo，否则执行hostReactor.getServiceInfoDirectlyFromServer获取serviceInfo

HostReactor

nacos-1.1.3/client/src/main/java/com/alibaba/nacos/client/naming/core/HostReactor.java

public class HostReactor {

    private static final long DEFAULT_DELAY = 1000L;

    private static final long UPDATE_HOLD_INTERVAL = 5000L;

    private final Map> futureMap = new HashMap>();

    private Map serviceInfoMap;

    private Map updatingMap;

    private PushReceiver pushReceiver;

    private EventDispatcher eventDispatcher;

    private NamingProxy serverProxy;

    private FailoverReactor failoverReactor;

    private String cacheDir;

    private ScheduledExecutorService executor;

    //......

    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);

        if (null == serviceObj) {
            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);

        return serviceInfoMap.get(serviceObj.getKey());
    }

    private ServiceInfo getServiceInfo0(String serviceName, String clusters) {

        String key = ServiceInfo.getKey(serviceName, clusters);

        return serviceInfoMap.get(key);
    }

    public void updateServiceNow(String serviceName, String clusters) {
        ServiceInfo oldService = getServiceInfo0(serviceName, clusters);
        try {

            String result = serverProxy.queryList(serviceName, clusters, pushReceiver.getUDPPort(), false);

            if (StringUtils.isNotEmpty(result)) {
                processServiceJSON(result);
            }
        } catch (Exception e) {
            NAMING_LOGGER.error("[NA] failed to update serviceName: " + serviceName, e);
        } finally {
            if (oldService != null) {
                synchronized (oldService) {
                    oldService.notifyAll();
                }
            }
        }
    }

    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);
        }
    }

    public ServiceInfo getServiceInfoDirectlyFromServer(final String serviceName, final String clusters) throws NacosException {
        String result = serverProxy.queryList(serviceName, clusters, 0, false);
        if (StringUtils.isNotEmpty(result)) {
            return JSON.parseObject(result, ServiceInfo.class);
        }
        return null;
    }

    //......
}

getServiceInfo首先判断failoverReactor.isFailoverSwitch()，如果是则返回failoverReactor.getService(key)；接着通过getServiceInfo0从serviceInfoMap查找，如果找不到则创建一个新的然后放入serviceInfoMap，同时放入updatingMap，执行updateServiceNow，再从updatingMap移除；如果从serviceInfoMap找出来的serviceObj在updatingMap中则等待UPDATE_HOLD_INTERVAL；最后执行scheduleUpdateIfAbsent，再从serviceInfoMap取出serviceInfo
updateServiceNow则从serverProxy.queryList获取结果，然后通过processServiceJSON解析并根据需要更新serviceInfoMap；scheduleUpdateIfAbsent方法判断futureMap是否有该任务，如果没有则添加一个UpdateTask
getServiceInfoDirectlyFromServer方法则直接请求serverProxy.queryList获取ServiceInfo

UpdateTask

nacos-1.1.3/client/src/main/java/com/alibaba/nacos/client/naming/core/HostReactor.java

    public class UpdateTask implements Runnable {
        long lastRefTime = Long.MAX_VALUE;
        private String clusters;
        private String serviceName;

        public UpdateTask(String serviceName, String clusters) {
            this.serviceName = serviceName;
            this.clusters = clusters;
        }

        @Override
        public void run() {
            try {
                ServiceInfo serviceObj = serviceInfoMap.get(ServiceInfo.getKey(serviceName, clusters));

                if (serviceObj == null) {
                    updateServiceNow(serviceName, clusters);
                    executor.schedule(this, DEFAULT_DELAY, TimeUnit.MILLISECONDS);
                    return;
                }

                if (serviceObj.getLastRefTime() <= lastRefTime) {
                    updateServiceNow(serviceName, clusters);
                    serviceObj = serviceInfoMap.get(ServiceInfo.getKey(serviceName, clusters));
                } else {
                    // if serviceName already updated by push, we should not override it
                    // since the push data may be different from pull through force push
                    refreshOnly(serviceName, clusters);
                }

                executor.schedule(this, serviceObj.getCacheMillis(), TimeUnit.MILLISECONDS);

                lastRefTime = serviceObj.getLastRefTime();
            } catch (Throwable e) {
                NAMING_LOGGER.warn("[NA] failed to update serviceName: " + serviceName, e);
            }

        }
    }

    public void refreshOnly(String serviceName, String clusters) {
        try {
            serverProxy.queryList(serviceName, clusters, pushReceiver.getUDPPort(), false);
        } catch (Exception e) {
            NAMING_LOGGER.error("[NA] failed to update serviceName: " + serviceName, e);
        }
    }

UpdateTask实现了Runnable接口，其run方法首先从serviceInfoMap获取serviceObj，获取不到则执行updateServiceNow，然后再次延时调度UpdateTask；可以从serviceInfoMap获取serviceObj的话则判断serviceObj.getLastRefTime()是否小于等于lastRefTime，是的话则执行updateServiceNow，否则执行refreshOnly；最后再次延时调度UpdateTask，并更新lastRefTime

NamingProxy

nacos-1.1.3/client/src/main/java/com/alibaba/nacos/client/naming/net/NamingProxy.java

public class NamingProxy {

    private static final int DEFAULT_SERVER_PORT = 8848;

    private int serverPort = DEFAULT_SERVER_PORT;

    private String namespaceId;

    private String endpoint;

    private String nacosDomain;

    private List serverList;

    private List serversFromEndpoint = new ArrayList();

    private long lastSrvRefTime = 0L;

    private long vipSrvRefInterMillis = TimeUnit.SECONDS.toMillis(30);

    private Properties properties;

    //......

    public String queryList(String serviceName, String clusters, int udpPort, boolean healthyOnly)
        throws NacosException {

        final Map params = new HashMap(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.NACOS_URL_BASE + "/instance/list", params, HttpMethod.GET);
    }

    //......
}

queryList方法会往/instance/list接口发送GET请求查询服务实例列表

小结

selectInstances首先从hostReactor获取serviceInfo，然后再从serviceInfo.getHosts()剔除非healty、非enabled、weight小于等于0的instance再返回；如果subscribe为true，则执行hostReactor.getServiceInfo获取serviceInfo，否则执行hostReactor.getServiceInfoDirectlyFromServer获取serviceInfo

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NacosNamingService中selectInstances的原理和作用

序

NacosNamingService

HostReactor

UpdateTask

NamingProxy

小结

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