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DynamicServerListLoadBalancer

public DynamicServerListLoadBalancer(IClientConfig clientConfig, IRule rule, IPing ping,                                         ServerList
   
     serverList, ServerListFilter
    
      filter,                                         ServerListUpdater serverListUpdater) {
           super(clientConfig, rule, ping);        this.serverListImpl = serverList;        this.filter = filter;        this.serverListUpdater = serverListUpdater;        if (filter instanceof AbstractServerListFilter) {
               ((AbstractServerListFilter) filter).setLoadBalancerStats(getLoadBalancerStats());        }        restOfInit(clientConfig); //     }
    
   

void restOfInit(IClientConfig clientConfig) {
           boolean primeConnection = this.isEnablePrimingConnections();        // turn this off to avoid duplicated asynchronous priming done in BaseLoadBalancer.setServerList()        this.setEnablePrimingConnections(false);        enableAndInitLearnNewServersFeature(); // serverListUpdater.start(updateAction);        updateListOfServers();        if (primeConnection && this.getPrimeConnections() != null) {
               this.getPrimeConnections()                    .primeConnections(getReachableServers());        }        this.setEnablePrimingConnections(primeConnection);        LOGGER.info("DynamicServerListLoadBalancer for client {} initialized: {}", clientConfig.getClientName(), this.toString());    } /**     * Feature that lets us add new instances (from AMIs) to the list of     * existing servers that the LB will use Call this method if you want this     * feature enabled     */    public void enableAndInitLearnNewServersFeature() {
           LOGGER.info("Using serverListUpdater {}", serverListUpdater.getClass().getSimpleName());        serverListUpdater.start(updateAction); // 开始调用updateAction    }

UpdateAction

protected final ServerListUpdater.UpdateAction updateAction = new ServerListUpdater.UpdateAction() {
           @Override        public void doUpdate() {
               updateListOfServers();        }    };

updateListOfServers

public void updateListOfServers() {
           List
   
     servers = new ArrayList
    
     ();        if (serverListImpl != null) {
    // NacosServerList            servers = serverListImpl.getUpdatedListOfServers();            LOGGER.debug("List of Servers for {} obtained from Discovery client: {}",                    getIdentifier(), servers);            if (filter != null) {
                   servers = filter.getFilteredListOfServers(servers);                LOGGER.debug("Filtered List of Servers for {} obtained from Discovery client: {}",                        getIdentifier(), servers);            }        }        updateAllServerList(servers);    }
    
   

ServerListUpdater

PollingServerListUpdater

PollingServerListUpdater.start

private static long LISTOFSERVERS_CACHE_UPDATE_DELAY = 1000; // msecs;private static int LISTOFSERVERS_CACHE_REPEAT_INTERVAL = 30 * 1000; // msecs;@Override    public synchronized void start(final UpdateAction updateAction) {
           if (isActive.compareAndSet(false, true)) {
               final Runnable wrapperRunnable = new Runnable() {
                   @Override                public void run() {
                       if (!isActive.get()) {
                           if (scheduledFuture != null) {
                               scheduledFuture.cancel(true);                        }                        return;                    }                    try {
                           // DynamicServerListLoadBalancer.doUpdate()                        updateAction.doUpdate();  // updateListOfServers()                        lastUpdated = System.currentTimeMillis();                    } catch (Exception e) {
                           logger.warn("Failed one update cycle", e);                    }                }            };            scheduledFuture = getRefreshExecutor().scheduleWithFixedDelay(                    wrapperRunnable,                    initialDelayMs, // 1s                    refreshIntervalMs, // 30s                    TimeUnit.MILLISECONDS            );            // 每30s执行1次        } else {
               logger.info("Already active, no-op");        }    }

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