dubbo学习（五）服务发布-zookeeper的连接

<dubbo:service interface="com.ywl.dubbo.TestApi" ref="testApi" retries="0"
               cluster="failfast" timeout="3000"/>

public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
    //暴露服务
    final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker);
    URL registryUrl = getRegistryUrl(originInvoker);
    //获取注册中心信息 - 在这一步会进行zookeeper的连接
    final Registry registry = getRegistry(originInvoker);
    //...

}

private Registry getRegistry(final Invoker<?> originInvoker) {
    URL registryUrl = getRegistryUrl(originInvoker);
    return registryFactory.getRegistry(registryUrl);
}

public Registry getRegistry(URL url) {
    url = url.setPath(RegistryService.class.getName())
            .addParameter(Constants.INTERFACE_KEY, RegistryService.class.getName())
.removeParameters(Constants.EXPORT_KEY, Constants.REFER_KEY);
    //key - zookeeper://zk的ip+端口/默认RegistryService路径名/group名/version号    String key = url.toServiceString();
    LOCK.lock();
    try {
        Registry registry = REGISTRIES.get(key);
        if (registry != null) {
            return registry;
        }        //缓存不存在 则创建注册信息
        registry = createRegistry(url);
        if (registry == null) {
            throw new IllegalStateException("Can not create registry " + url);
        }
        REGISTRIES.put(key, registry);
        return registry;
    } finally {
        LOCK.unlock();
    }
}

public Registry createRegistry(URL url) {
    return new ZookeeperRegistry(url, zookeeperTransporter);
}//步骤一 加载本地配置到内存中

public AbstractRegistry(URL url) {
    setUrl(url);
    syncSaveFile = url.getParameter(Constants.REGISTRY_FILESAVE_SYNC_KEY, false);
    String filename = url.getParameter(Constants.FILE_KEY, System.getProperty("user.home") + "/.dubbo/dubbo-registry-" + url.getParameter(Constants.APPLICATION_KEY) + "-" + url.getAddress() + ".cache");
    //获取配置信息本地缓存的文件    File file = null;
    if (ConfigUtils.isNotEmpty(filename)) {
        file = new File(filename);
        if (!file.exists() && file.getParentFile() != null && !file.getParentFile().exists()) {
            if (!file.getParentFile().mkdirs()) {
                throw new IllegalArgumentException("Invalid registry store file " + file + ", cause: Failed to create directory " + file.getParentFile() + "!");
            }
        }
    }    this.file = file;    //如果存在本地缓存文件则从文件中加载属性，文件中主要存放的是每个接口的注册中心的地址    loadProperties();
    //通知触发所有监听器    notify(url.getBackupUrls());
}
步骤二：检测注册中心，如果失败了进行重连public FailbackRegistry(URL url) {
    //...
    this.retryFuture = retryExecutor.scheduleWithFixedDelay(new Runnable() {
        @Override
        public void run() {
            try {                //建立线程池检测注册中心，如果失败了进行重连                retry();
            } catch (Throwable t) {
                logger.error("Unexpected error occur at failed retry, cause: " + t.getMessage(), t);
            }
        }
    }, retryPeriod, retryPeriod, TimeUnit.MILLISECONDS);
}步骤三：zookeeper连接
public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) {
    //...    //初始化zookeeper，连接zookeeper    zkClient = zookeeperTransporter.connect(url);
    //订阅监听 如果连接断开重连
    zkClient.addStateListener(new StateListener() {
        @Override
        public void stateChanged(int state) {
            if (state == RECONNECTED) {
                try {
                    recover();
                } catch (Exception e) {
                    logger.error(e.getMessage(), e);
                }
            }
        }
    });
}