【SpringCloud原理】Ribbon核心组件以及运行原理源码剖析(三)

发布于 2022-6-16 17:49
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说完BaseLoadBalancer这个实现类,接下来说一下DynamicServerListLoadBalancer实现类

DynamicServerListLoadBalancer

public class DynamicServerListLoadBalancer<T extends Server> extends BaseLoadBalancer {
    private static final Logger LOGGER = LoggerFactory.getLogger(DynamicServerListLoadBalancer.class);

    volatile ServerList<T> serverListImpl;
    volatile ServerListFilter<T> filter;
    protected final ServerListUpdater.UpdateAction updateAction = new ServerListUpdater.UpdateAction() {
        @Override
        public void doUpdate() {
            updateListOfServers();
        }
    };
    protected volatile ServerListUpdater serverListUpdater;    
    public DynamicServerListLoadBalancer(IClientConfig clientConfig, IRule rule, IPing ping,
                                         ServerList<T> serverList, ServerListFilter<T> 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);
    }    
    
    @Override
    public void setServersList(List lsrv) {
        super.setServersList(lsrv);
        List<T> serverList = (List<T>) lsrv;
        Map<String, List<Server>> serversInZones = new HashMap<String, List<Server>>();
        for (Server server : serverList) {
            // make sure ServerStats is created to avoid creating them on hot
            // path
            getLoadBalancerStats().getSingleServerStat(server);
            String zone = server.getZone();
            if (zone != null) {
                zone = zone.toLowerCase();
                List<Server> servers = serversInZones.get(zone);
                if (servers == null) {
                    servers = new ArrayList<Server>();
                    serversInZones.put(zone, servers);
                }
                servers.add(server);
            }
        }
        setServerListForZones(serversInZones);
    }

    protected void setServerListForZones(
            Map<String, List<Server>> zoneServersMap) {
        LOGGER.debug("Setting server list for zones: {}", zoneServersMap);
        getLoadBalancerStats().updateZoneServerMapping(zoneServersMap);
    }

    @VisibleForTesting
    public void updateListOfServers() {
        List<T> servers = new ArrayList<T>();
        if (serverListImpl != null) {
            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);
    }

    /**
     * Update the AllServer list in the LoadBalancer if necessary and enabled
     * 
     * @param ls
     */
    protected void updateAllServerList(List<T> ls) {
        // other threads might be doing this - in which case, we pass
        if (serverListUpdateInProgress.compareAndSet(false, true)) {
            try {
                for (T s : ls) {
                    s.setAlive(true); // set so that clients can start using these
                                      // servers right away instead
                                      // of having to wait out the ping cycle.
                }
                setServersList(ls);
                super.forceQuickPing();
            } finally {
                serverListUpdateInProgress.set(false);
            }
        }
    }
}

 

DynamicServerListLoadBalancer继承自BaseLoadBalancer,DynamicServerListLoadBalancer主要是对BaseLoadBalancer功能进行扩展。

 

成员变量

serverListImpl:上面说过,通过这个接口获取服务列表

filter:起到过滤的作用,一般不care

updateAction:是个匿名内部类,实现了doUpdate方法,会调用updateListOfServers方法

serverListUpdater:上面说到过,默认就是唯一的实现类PollingServerListUpdater,也就是每个30s就会调用传入的updateAction的doUpdate方法。

 

这不是巧了么,serverListUpdater的start方法需要一个updateAction,刚刚好成员变量有个updateAction的匿名内部类的实现,所以serverListUpdater的start方法传入的updateAction的实现其实就是这个匿名内部类。


那么哪里调用了serverListUpdater的start方法传入了updateAction呢?是在构造的时候调用的,具体的调用链路是调用 restOfInit -> enableAndInitLearnNewServersFeature(),这里就不贴源码了

 

文章转自公众号:三友的java日记

已于2022-6-16 17:49:51修改
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