【知识库】--Dubbo ReferenceBean获取-- 调用RegistryDirectory.notify -- 源码过程（254）

回顾上一篇文章：获取ReferenceBean过程中SPI自适应到RegistryProtocol类后，调用refer方法：

@SuppressWarnings("unchecked")
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
url = url.setProtocol(url.getParameter(Constants.REGISTRY_KEY, Constants.DEFAULT_REGISTRY)).removeParameter(Constants.REGISTRY_KEY);
Registry registry = registryFactory.getRegistry(url);
if (RegistryService.class.equals(type)) {
return proxyFactory.getInvoker((T) registry, type, url);
}

// group="a,b" or group="*"
Map<String, String> qs = StringUtils.parseQueryString(url.getParameterAndDecoded(Constants.REFER_KEY));
String group = qs.get(Constants.GROUP_KEY);
if (group != null && group.length() > 0) {
if ((Constants.COMMA_SPLIT_PATTERN.split(group)).length > 1
|| "*".equals(group)) {
return doRefer(getMergeableCluster(), registry, type, url);
}
}
return doRefer(cluster, registry, type, url);
}

private Cluster getMergeableCluster() {
return ExtensionLoader.getExtensionLoader(Cluster.class).getExtension("mergeable");
}

private <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
RegistryDirectory<T> directory = new RegistryDirectory<T>(type, url);
directory.setRegistry(registry);
directory.setProtocol(protocol);
URL subscribeUrl = new URL(Constants.CONSUMER_PROTOCOL, NetUtils.getLocalHost(), 0, type.getName(), directory.getUrl().getParameters());
if (!Constants.ANY_VALUE.equals(url.getServiceInterface())
&& url.getParameter(Constants.REGISTER_KEY, true)) {
registry.register(subscribeUrl.addParameters(Constants.CATEGORY_KEY, Constants.CONSUMERS_CATEGORY,
Constants.CHECK_KEY, String.valueOf(false)));
}
directory.subscribe(subscribeUrl.addParameter(Constants.CATEGORY_KEY,
Constants.PROVIDERS_CATEGORY
+ "," + Constants.CONFIGURATORS_CATEGORY
+ "," + Constants.ROUTERS_CATEGORY));
return cluster.join(directory);
}

1

自适应到：com.alibaba.dubbo.registry.integration.RegistryDirectory#subscribe方法

directory.subscribe(subscribeUrl.addParameter(Constants.CATEGORY_KEY,
Constants.PROVIDERS_CATEGORY
+ "," + Constants.CONFIGURATORS_CATEGORY
+ "," + Constants.ROUTERS_CATEGORY));

2 方法实现：

public void subscribe(URL url) {
setConsumerUrl(url);
registry.subscribe(url, this);
}

3 订阅实现：

com.alibaba.dubbo.registry.support.FailbackRegistry#subscribe

@Override
public void subscribe(URL url, NotifyListener listener) {
super.subscribe(url, listener);
removeFailedSubscribed(url, listener);
try {
// 向服务器端发送订阅请求
doSubscribe(url, listener);
} catch (Exception e) {
Throwable t = e;

List<URL> urls = getCacheUrls(url);
if (urls != null && urls.size() > 0) {
notify(url, listener, urls);
logger.error("Failed to subscribe " + url + ", Using cached list: " + urls + " from cache file: " + getUrl().getParameter(Constants.FILE_KEY, System.getProperty("user.home") + "/dubbo-registry-" + url.getHost() + ".cache") + ", cause: " + t.getMessage(), t);
} else {
// 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);
boolean skipFailback = t instanceof SkipFailbackWrapperException;
if (check || skipFailback) {
if (skipFailback) {
t = t.getCause();
}
throw new IllegalStateException("Failed to subscribe " + url + ", cause: " + t.getMessage(), t);
} else {
logger.error("Failed to subscribe " + url + ", waiting for retry, cause: " + t.getMessage(), t);
}
}

// 将失败的订阅请求记录到失败列表，定时重试
addFailedSubscribed(url, listener);
}
}

4 重点：

// 向服务器端发送订阅请求
doSubscribe(url, listener);

5 参考zookeeper实现：

com.alibaba.dubbo.registry.zookeeper.ZookeeperRegistry#doSubscribe

protected void doSubscribe(final URL url, final NotifyListener listener) {
try {
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>();
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);
}
zkClient.create(path, false);
List<String> children = zkClient.addChildListener(path, zkListener);
if (children != null) {
urls.addAll(toUrlsWithEmpty(url, path, children));
}
}
notify(url, listener, urls);
}
} catch (Throwable e) {
throw new RpcException("Failed to subscribe " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);
}
}

6 上面除了注册回调函数外，最后调用了（回调函数，主动触发）

notify(url, listener, urls);

即：

com.alibaba.dubbo.registry.support.FailbackRegistry#notify

实现：

@Override
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");
}
try {
doNotify(url, listener, urls);
} catch (Exception t) {
// 将失败的通知请求记录到失败列表，定时重试
Map<NotifyListener, List<URL>> listeners = failedNotified.get(url);
if (listeners == null) {
failedNotified.putIfAbsent(url, new ConcurrentHashMap<NotifyListener, List<URL>>());
listeners = failedNotified.get(url);
}
listeners.put(listener, urls);
logger.error("Failed to notify for subscribe " + url + ", waiting for retry, cause: " + t.getMessage(), t);
}
}

跟进：

protected void doNotify(URL url, NotifyListener listener, List<URL> urls) {
super.notify(url, listener, urls);
}

跟进到：com.alibaba.dubbo.registry.support.AbstractRegistry#notify

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) {
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);
saveProperties(url);
listener.notify(categoryList);
}
}

7 上面最终执行了 回调！

listener.notify(categoryList);

也就是com.alibaba.dubbo.registry.integration.RegistryDirectory#notify

public synchronized void notify(List<URL> urls) {
List<URL> invokerUrls = new ArrayList<URL>();
List<URL> routerUrls = new ArrayList<URL>();
List<URL> configuratorUrls = new ArrayList<URL>();

for (URL url : urls) {
String protocol = url.getProtocol();
String category = url.getParameter(Constants.CATEGORY_KEY, Constants.DEFAULT_CATEGORY);
if (Constants.ROUTERS_CATEGORY.equals(category) || Constants.ROUTE_PROTOCOL.equals(protocol)) {
routerUrls.add(url);
} else if (Constants.CONFIGURATORS_CATEGORY.equals(category) || Constants.OVERRIDE_PROTOCOL.equals(protocol)) {
configuratorUrls.add(url);
} else if (Constants.PROVIDERS_CATEGORY.equals(category)) {
invokerUrls.add(url);
} else {
logger.warn("Unsupported category " + category + " in notified url: " + url + " from registry " + getUrl().getAddress() + " to consumer " + NetUtils.getLocalHost());
}
}

// routers
if (routerUrls.size() > 0) {
List<Router> routers = toRouters(routerUrls);
if (routers != null) { // null - do nothing
setRouters(routers);
}
}

// configurators
if (configuratorUrls.size() > 0) {
this.configurators = toConfigurators(configuratorUrls);
}
List<Configurator> localConfigurators = this.configurators; // local reference
// 合并override参数
this.overrideDirectoryUrl = directoryUrl;
if (localConfigurators != null && localConfigurators.size() > 0) {
for (Configurator configurator : localConfigurators) {
this.overrideDirectoryUrl = configurator.configure(overrideDirectoryUrl);
}
}

if (configuratorUrls.size() > 0) {
logger.info("unconfigured directory url without provider params: " + this.directoryUrl
+ ", configured directory url without provider params: " + this.overrideDirectoryUrl);
}

// providers
refreshInvoker(invokerUrls);
}

等待被动回调和本次主动回调最终都会调用RegistryDirectory.notify。

8 最后就会触发refreshInvoker

／* 根据invokerURL列表转换为invoker列表。转换规则如下：
* 1.如果url已经被转换为invoker，则不在重新引用，直接从缓存中获取，注意如果url中任何一个参数变更也会重新引用
* 2.如果传入的invoker列表不为空，则表示最新的invoker列表
* 3.如果传入的invokerUrl列表是空，则表示只是下发的override规则或route规则，需要重新交叉对比，决定是否需要重新引用。
*
* @param invokerUrls 传入的参数不能为null
*/
private void refreshInvoker(List<URL> invokerUrls) {
if (invokerUrls != null && invokerUrls.size() == 1 && invokerUrls.get(0) != null && Constants.EMPTY_PROTOCOL.equals(invokerUrls.get(0).getProtocol())) {
this.forbidden = true; // 禁止访问
overrideDirectoryUrl = overrideDirectoryUrl.addParameters(Constants.INVOKER_INSIDE_INVOKERS_KEY, "", Constants.INVOKER_INSIDE_INVOKER_COUNT_KEY, "0");
this.methodInvokerMap = null; // 置空列表
destroyAllInvokers(); // 关闭所有Invoker
} else {
this.forbidden = false; // 允许访问
Map<String, Invoker<T>> oldUrlInvokerMap = this.urlInvokerMap; // local reference
if (invokerUrls.size() == 0 && this.lastInvokerUrls != null) {
invokerUrls.addAll(this.lastInvokerUrls);
} else {
this.lastInvokerUrls = new HashSet<URL>();
this.lastInvokerUrls.addAll(invokerUrls);//缓存invokerUrls列表，便于交叉对比
}

if (invokerUrls.size() == 0) return;

Map<String, Invoker<T>> newUrlInvokerMap = toInvokers(invokerUrls);// 将URL列表转成Invoker列表
// state change
//如果计算错误，则不进行处理.
//比如所有provider都标记为下线状态，这样其实最后一个provider是下不了的
if (newUrlInvokerMap == null || newUrlInvokerMap.size() == 0) {
logger.error(new IllegalStateException("urls to invokers error .invokerUrls.size :" + invokerUrls.size() + ", invoker.size :0. urls :" + invokerUrls.toString()));
return;
}
Map<String, List<Invoker<T>>> newMethodInvokerMap = toMethodInvokers(newUrlInvokerMap); // 换方法名映射Invoker列表

this.methodInvokerMap = multiGroup ? toMergeMethodInvokerMap(newMethodInvokerMap) : newMethodInvokerMap;
this.urlInvokerMap = newUrlInvokerMap;
try {
destroyUnusedInvokers(oldUrlInvokerMap, newUrlInvokerMap); // 关闭未使用的Invoker
} catch (Exception e) {
logger.warn("destroyUnusedInvokers error. ", e);
}

List<String> invokerUrlString = new ArrayList<String>();
for (URL invoker : invokerUrls) {
invokerUrlString.add(invoker.toString());
}
overrideDirectoryUrl = overrideDirectoryUrl.addParameters(
Constants.INVOKER_INSIDE_INVOKERS_KEY, URL.encode(CollectionUtils.join(invokerUrlString, ";")),
Constants.INVOKER_INSIDE_INVOKER_COUNT_KEY, String.valueOf(invokerUrls.size()));
}
}

9 跟进com.alibaba.dubbo.registry.integration.RegistryDirectory#toInvokers

/**
* 将urls转成invokers,如果url已经被refer过，不再重新引用。
*
* @param urls
* @return invokers
*/
private Map<String, Invoker<T>> toInvokers(List<URL> urls) {
Map<String, Invoker<T>> result = new HashMap<String, Invoker<T>>();
if (urls == null || urls.size() == 0) return result;

Set<String> keys = new HashSet<String>();
for (URL providerUrl : urls) {
if (!acceptProtocol(providerUrl)) {
continue;
}
if (!acceptTransport(providerUrl)) {
continue;
}

URL url = mergeUrl(providerUrl);

String key = url.toFullString(); // URL参数是排序的
if (keys.contains(key)) { // 重复URL
continue;
}
keys.add(key);

// 缓存key为没有合并消费端参数的URL，不管消费端如何合并参数，如果服务端URL发生变化，则重新refer
Map<String, Invoker<T>> localUrlInvokerMap = this.urlInvokerMap; // local reference
Invoker<T> invoker = localUrlInvokerMap == null ? null : localUrlInvokerMap.get(key);
if (invoker == null) { // 缓存中没有，重新refer
try {
if (isEnable(url)) {
invoker = new InvokerDelegete<T>(protocol.refer(serviceType, url), url, providerUrl);
}
} catch (Throwable t) {
logger.error("Failed to refer invoker for interface:" + serviceType + ",url:(" + url + ")" + t.getMessage(), t);
}
if (invoker != null) { // 将新的引用放入缓存
result.put(key, invoker);
}
} else {
result.put(key, invoker);
}
}
keys.clear();
return result;
}

到此目录notify方法调用 源码过程完毕！