Ribbon负载均衡策略DynamicServerListLoadBalancer的ServerListUpdater解读

最新推荐文章于 2024-04-10 13:41:09 发布

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最新推荐文章于 2024-04-10 13:41:09 发布 · 1.3w 阅读

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#Ribbon

一 DynamicServerListLoadBalancer在类图中的位置

二 DynamicServerListLoadBalancer源码解读

1 关键代码请见注释

2 源码位置：ribbon-master\ribbon-loadbalancer\src\main\java\com\netflix\loadbalancer\DynamicServerListLoadBalancer.java

//继承于BaseLoadBalancer类，它是对基础负载均衡器的扩展。实现了下面两个功能
//服务实例在运行期间的动态更新
//对服务器实例清单的过滤功能，可以通过过滤器来选择地获取一批服务实例清单
public class DynamicServerListLoadBalancer<T extends Server> extends BaseLoadBalancer {
    private static final Logger LOGGER = LoggerFactory.getLogger(DynamicServerListLoadBalancer.class);

    boolean isSecure = false;
    boolean useTunnel = false;

    protected AtomicBoolean serverListUpdateInProgress = new AtomicBoolean(false);
    //服务列表操作对象
    //这里泛型T是一个Server的子类，代表了一个具体的服务实例扩展类
    volatile ServerList<T> serverListImpl;

    volatile ServerListFilter<T> filter;

    protected final ServerListUpdater.UpdateAction updateAction = new ServerListUpdater.UpdateAction() {
        @Override
        public void doUpdate() {
            updateListOfServers();
        }
    };
    
    //用于触发向Eureka Server去获取服务实例清单以及如何在获取到服务实例清单后更新本地的服务实例清单
    //这个对象实现的是对Server的更新，又被称为服务更新器
    protected volatile ServerListUpdater serverListUpdater;

    public DynamicServerListLoadBalancer() {
        super();
    }

    @Deprecated
    public DynamicServerListLoadBalancer(IClientConfig clientConfig, IRule rule, IPing ping,
            ServerList<T> serverList, ServerListFilter<T> filter) {
        this(
                clientConfig,
                rule,
                ping,
                serverList,
                filter,
                new PollingServerListUpdater()
        );
    }

    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);
    }

    public DynamicServerListLoadBalancer(IClientConfig clientConfig) {
        initWithNiwsConfig(clientConfig);
    }
    
    @Override
    public void initWithNiwsConfig(IClientConfig clientConfig) {
        try {
            super.initWithNiwsConfig(clientConfig);
            String niwsServerListClassName = clientConfig.getPropertyAsString(
                    CommonClientConfigKey.NIWSServerListClassName,
                    DefaultClientConfigImpl.DEFAULT_SEVER_LIST_CLASS);

            ServerList<T> niwsServerListImpl = (ServerList<T>) ClientFactory
                    .instantiateInstanceWithClientConfig(niwsServerListClassName, clientConfig);
            this.serverListImpl = niwsServerListImpl;

            if (niwsServerListImpl instanceof AbstractServerList) {
                AbstractServerListFilter&