工厂模式的Registry
本想按照服务发布和服务引用来写，但是感觉先理解Registry，后面发布和服务引用里面可以省略掉这里的东西，更方便关注主流程的东西。
工厂模式创建Registry
Registry提供服务的注册，订阅功能，采用工厂模式创建，看图：
左边Registry代表产品体系，右边RegistryFactory工厂生成Registry，每个具体factory生成具体的Registry，分离产品的创建。后期只需要增加具体的工厂生成具体的产品。
RegistryFactory
RegistryFactory也是采用dubbo的扩展点机制加载，默认dubbo，我例子用的是zk，后面讲解也以zk为主。
@SPI("dubbo")
public interface RegistryFactory {
@Adaptive({"protocol"})
Registry getRegistry(URL url);
}
>AbstractRegistryFactory
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);
String key = url.toServiceString();
// 锁定注册中心获取过程，保证注册中心单一实例
LOCK.lock();
try {
Registry registry = REGISTRIES.get(key);
if (registry != null) {
return registry;
}
//模板模式，子类具体实现
registry = createRegistry(url);
if (registry == null) {
throw new IllegalStateException("Can not create registry " + url);
}
REGISTRIES.put(key, registry);
return registry;
} finally {
// 释放锁
LOCK.unlock();
}
}
//模板模式，createRegistry有具体的工厂生成
protected abstract Registry createRegistry(URL url);ZookeeperRegistryFactory
public class ZookeeperRegistryFactory extends AbstractRegistryFactory {
private ZookeeperTransporter zookeeperTransporter;
//ZookeeperTransporter通过扩展点加载injectExtension
public void setZookeeperTransporter(ZookeeperTransporter zookeeperTransporter) {
this.zookeeperTransporter = zookeeperTransporter;
}
//创建ZookeeperRegistry
public Registry createRegistry(URL url) {
return new ZookeeperRegistry(url, zookeeperTransporter);
}
}
这样就生成了具体的产品ZookeeperRegistry。
Registry
AbstractRegistry
RegistryService接口定义了注册的几个接口，包括注册、订阅、取消注册、取消订阅接口和服务lookup查找接口，在其继承体系中AbstractRegistry主要提供服务的本地文件缓存功能，其线程安全通过：
- 异步情况下通过线程池的newFixedThreadPool（1），只有一个核心线程处理来保障；
- 建立临时文件.lcok，通过FileLock加锁；
- 通过version。
对RegistryService接口的实现，主要是入参的存储，例如
public void register(URL url) {
if (url == null) {
throw new IllegalArgumentException("register url == null");
}
if (logger.isInfoEnabled()){
logger.info("Register: " + url);
}
//服务的本地存储
registered.add(url);
}
public void subscribe(URL url, NotifyListener listener) {
if (url == null) {
throw new IllegalArgumentException("subscribe url == null");
}
if (listener == null) {
throw new IllegalArgumentException("subscribe listener == null");
}
if (logger.isInfoEnabled()){
logger.info("Subscribe: " + url);
}
Set<NotifyListener> listeners = subscribed.get(url);
if (listeners == null) {
subscribed.putIfAbsent(url, new ConcurrentHashSet<NotifyListener>());
listeners = subscribed.get(url);
}
//监听存储
listeners.add(listener);
}
其他类似。
FailbackRegistry
继承体系中FailbackRegistry，主要提供服务注册、订阅失败情况的5秒定时重试机制，并且通过模板模式，定义处理注册订阅流程，具体实现由具体子类实现。
例如
@Override
public void register(URL url) {
super.register(url);
failedRegistered.remove(url);
failedUnregistered.remove(url);
try {
// 向服务器端发送注册请求
doRegister(url);
} catch (Exception e) {
Throwable t = e;
// 如果开启了启动时检测，则直接抛出异常
boolean check = getUrl().getParameter(Constants.CHECK_KEY, true)
&& url.getParameter(Constants.CHECK_KEY, true)
&& ! Constants.CONSUMER_PROTOCOL.equals(url.getProtocol());
boolean skipFailback = t instanceof SkipFailbackWrapperException;
if (check || skipFailback) {
if(skipFailback) {
t = t.getCause();
}
throw new IllegalStateException("Failed to register " + url + " to registry " + getUrl().getAddress() + ", cause: " + t.getMessage(), t);
} else {
logger.error("Failed to register " + url + ", waiting for retry, cause: " + t.getMessage(), t);
}
// 将失败的注册请求记录到失败列表，定时重试
failedRegistered.add(url);
}
}
// ==== 模板方法 ====
protected abstract void doRegister(URL url);
其他订阅等接口类似处理。
ZookeeperRegistry
我配置的注册是zk，所以看下ZookeeperRegistry，主要看下注册和订阅接口的实现。
构造
//构造，这里的url是注册中心的地址
public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) {
super(url);
if (url.isAnyHost()) {
throw new IllegalStateException("registry address == null");
}
//group主要用在后面的注册的服务路径里面，如果服务本身没有group使用默认dubbo
String group = url.getParameter(Constants.GROUP_KEY, DEFAULT_ROOT);
if (! group.startsWith(Constants.PATH_SEPARATOR)) {
group = Constants.PATH_SEPARATOR + group;
}
this.root = group;
//取得zk的连接
zkClient = zookeeperTransporter.connect(url);
//zk的监听，zk状态变换，需要将本地失败的注册和订阅重新注册和订阅
zkClient.addStateListener(new StateListener() {
public void stateChanged(int state) {
if (state == RECONNECTED) {
try {
recover();
} catch (Exception e) {
logger.error(e.getMessage(), e);
}
}
}
});
}doRegister
//注册
protected void doRegister(URL url) {
try {
//通过zkClient实现，了解zk的应该知道zk类似于目录结构，这里也是建立服务的目录结构
//toUrlPath方法转将注册的服务转换为路径，/group(没有就是dubbo)/接口名/provider(默认provider，根据url中category参数决定，现在基本这几种：consumer、routers、configurators)/服务信息（url形式）
//第二个主要表示创建的临时节点还是持久化的节点，一般路径都是持久的，只有最后服务信息是临时的
zkClient.create(toUrlPath(url), url.getParameter(Constants.DYNAMIC_KEY, true));
} catch (Throwable e) {
throw new RpcException("Failed to register " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);
}
}doSubscribe
//订阅服务，类似zk的watch吧，入参NotifyListener为回调接口
protected void doSubscribe(final URL url, final NotifyListener listener) {
try {
//这个if暂时不关心，最后还是到else那里
if (Constants.ANY_VALUE.equals(url.getServiceInterface())) {
String root = toRootPath();
ConcurrentMap<NotifyListener, ChildListener> listeners = zkListeners.get(url);
if (listeners == null) {
zkListeners.putIfAbsent(url, new ConcurrentHashMap<NotifyListener, ChildListener>());
listeners = zkListeners.get(url);
}
ChildListener zkListener = listeners.get(listener);
if (zkListener == null) {
listeners.putIfAbsent(listener, new ChildListener() {
public void childChanged(String parentPath, List<String> currentChilds) {
for (String child : currentChilds) {
if (! anyServices.contains(child)) {
anyServices.add(child);
subscribe(url.setPath(child).addParameters(Constants.INTERFACE_KEY, child,
Constants.CHECK_KEY, String.valueOf(false)), listener);
}
}
}
});
zkListener = listeners.get(listener);
}
zkClient.create(root, false);
List<String> services = zkClient.addChildListener(root, zkListener);
if (services != null && services.size() > 0) {
anyServices.addAll(services);
for (String service : services) {
subscribe(url.setPath(service).addParameters(Constants.INTERFACE_KEY, service,
Constants.CHECK_KEY, String.valueOf(false)), listener);
}
}
} else {
List<URL> urls = new ArrayList<URL>();
//url中的参数category可以配置多个，相当于watch多个目录，这里for下
for (String path : toCategoriesPath(url)) {
ConcurrentMap<NotifyListener, ChildListener> listeners = zkListeners.get(url);
if (listeners == null) {
zkListeners.putIfAbsent(url, new ConcurrentHashMap<NotifyListener, ChildListener>());
listeners = zkListeners.get(url);
}
ChildListener zkListener = listeners.get(listener);
if (zkListener == null) {
listeners.putIfAbsent(listener, new ChildListener() {
public void childChanged(String parentPath, List<String> currentChilds) {
ZookeeperRegistry.this.notify(url, listener, toUrlsWithEmpty(url, parentPath, currentChilds));
}
});
zkListener = listeners.get(listener);
}
//watch的目录不存在就创建
zkClient.create(path, false);
List<String> children = zkClient.addChildListener(path, zkListener);
if (children != null) {
//toUrlsWithEmpty是将watch的路径转换为url，dubbo中服务信息，参数传递很多都是url来处理的
urls.addAll(toUrlsWithEmpty(url, path, children));
}
}
//这里最重要的，回调listen
notify(url, listener, urls);
}
} catch (Throwable e) {
throw new RpcException("Failed to subscribe " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);
}
}notify方法最后的处理逻辑在AbstractRegistry里面。
//AbstractRegistry
protected void notify(URL url, NotifyListener listener, List<URL> urls) {
if (url == null) {
throw new IllegalArgumentException("notify url == null");
}
if (listener == null) {
throw new IllegalArgumentException("notify listener == null");
}
if ((urls == null || urls.size() == 0)
&& ! Constants.ANY_VALUE.equals(url.getServiceInterface())) {
logger.warn("Ignore empty notify urls for subscribe url " + url);
return;
}
if (logger.isInfoEnabled()) {
logger.info("Notify urls for subscribe url " + url + ", urls: " + urls);
}
Map<String, List<URL>> result = new HashMap<String, List<URL>>();
for (URL u : urls) {
//isMatch主要做匹配，group，接口，版本，watch目录等是否一致
if (UrlUtils.isMatch(url, u)) {
String category = u.getParameter(Constants.CATEGORY_KEY, Constants.DEFAULT_CATEGORY);
List<URL> categoryList = result.get(category);
if (categoryList == null) {
categoryList = new ArrayList<URL>();
result.put(category, categoryList);
}
categoryList.add(u);
}
}
if (result.size() == 0) {
return;
}
Map<String, List<URL>> categoryNotified = notified.get(url);
if (categoryNotified == null) {
notified.putIfAbsent(url, new ConcurrentHashMap<String, List<URL>>());
categoryNotified = notified.get(url);
}
for (Map.Entry<String, List<URL>> entry : result.entrySet()) {
String category = entry.getKey();
List<URL> categoryList = entry.getValue();
categoryNotified.put(category, categoryList);
//缓存到本地文件
saveProperties(url);
//回调listen
listener.notify(categoryList);
}
}做本地缓存和listen回调。
取消注册和取消订阅处理方式差不多，不做解释。
