開篇
這篇文章的目的是嘗試將dubbo的服務(wù)引用過程盡量描述的清楚些，主要核心在于注冊consumer，訂閱provider并生成reference的invoker對象。
另外，嘗試通過zookeeper訂閱過程回調(diào)描述清楚provider變更時consumer如何感知provider的增刪操作。
注冊中心類依賴圖
dubbo注冊中心類圖
說明：
- 關(guān)注ZookeeperRegistry、FailbackRegistry、AbastractRegistry的類關(guān)系。
- 關(guān)注上述三者的依賴關(guān)系由于理解consumer的注冊過程。
consumer初始化過程時序圖
consumer初始化時序圖
說明：
1、consumer端在初始化bean后的afterPropertiesSet()方法中進行初始化動作。
2、consumer注冊自身到zk的/dubbo/xxx_interface/consumer節(jié)點下面
3、consumer訂閱zk的/dubbo/xxx_interface/provider|configor|routers服務(wù)
4、訂閱節(jié)點有變化的時候通知變更
5、所有訂閱的服務(wù)保存在RegistyDirectory目錄中供發(fā)起RPC調(diào)用的時候cluster調(diào)用
整體流程圖總結(jié)
整體流程圖總結(jié)
說明：
以下內(nèi)容參考自dubbo剖析：二 服務(wù)引用
1、引用配置及配置初始化
該部分以Spring配置及ReferenceBean為入口，主要在ReferenceConfig中進行。
ReferenceConfig依賴RegistryProtocol完成了 "服務(wù)引用者注冊"、"服務(wù)提供者訂閱"和"Invoker創(chuàng)建" 的工作；
ReferenceConfig依賴JavassistProxyFactory完成了 "代理對象生成" 的工作；
2、注冊中心訂閱 & Invoker生成與獲取
該部分主要由RegistryDirectory和FailfastCluster實現(xiàn)。
通過ReferenceConfig調(diào)用RegistryDirectory的subscribe方法，觸發(fā)了對服務(wù)提供者url的訂閱及監(jiān)聽，在監(jiān)聽過程中RegistryDirectory借助DubboProtocol完成了Invoker的創(chuàng)建工作，并保存了服務(wù)引用url和Invoker的關(guān)系；
通過ReferenceConfig調(diào)用FailfastCluster的join方法，完成了對Invoker對象的獲??；
3、生成代理對象
該部分主要由JavassistProxyFactory完成。
以ReferenceConfig調(diào)用JavassistProxyFactory的getProxy方法為入口，傳入Invoker；
新創(chuàng)建了InvokerInvocationHandler，并使用dubbo自己的動態(tài)代理工具Proxy最終生成代理對象T ref；
dubbo 服務(wù)引用過程 - 階段一
說明：
1、ReferenceBean的afterPropertiesSet()方法作為consumer的初始化入口。
2、afterPropertiesSet()內(nèi)部調(diào)用getObject() -> get()執(zhí)行ReferenceConfig的get()方法。
3、ReferenceConfig執(zhí)行g(shù)et() -> init() -> createProxy()進入consumer的代理創(chuàng)建過程。
4、createProxy()方法內(nèi)部遍歷注冊中心生成consumer需要注冊的注冊中心URL地址。
5、關(guān)注refprotocol.refer方法，進入consumer引用provider的邏輯。
public class ReferenceBean<T> extends ReferenceConfig<T> implements
FactoryBean, ApplicationContextAware, InitializingBean, DisposableBean {
@SuppressWarnings({"unchecked"})
public void afterPropertiesSet() throws Exception {
// 省略相關(guān)代碼
Boolean b = isInit();
if (b == null && getConsumer() != null) {
b = getConsumer().isInit();
}
if (b != null && b.booleanValue()) {
// 獲取referenceBean入口
getObject();
}
}
public Object getObject() throws Exception {
return get();
}
}
public class ReferenceConfig<T> extends AbstractReferenceConfig {
public synchronized T get() {
if (ref == null) {
init();
}
return ref;
}
private void init() {
// 組裝參數(shù)
Map<String, String> map = new HashMap<String, String>();
Map<Object, Object> attributes = new HashMap<Object, Object>();
map.put(Constants.SIDE_KEY, Constants.CONSUMER_SIDE);
map.put(Constants.DUBBO_VERSION_KEY, Version.getVersion());
map.put(Constants.TIMESTAMP_KEY, String.valueOf(System.currentTimeMillis()));
if (ConfigUtils.getPid() > 0) {
map.put(Constants.PID_KEY, String.valueOf(ConfigUtils.getPid()));
}
// 創(chuàng)建服務(wù)引用的入口
ref = createProxy(map);
ConsumerModel consumerModel = new ConsumerModel(getUniqueServiceName(), this, ref, interfaceClass.getMethods());
ApplicationModel.initConsumerModel(getUniqueServiceName(), consumerModel);
}
private T createProxy(Map<String, String> map) {
if (isJvmRefer) {
// 省略相關(guān)代碼
} else {
// user specified URL, could be peer-to-peer address,
// or register center's address.
// 處理直連的情況
if (url != null && url.length() > 0) {
String[] us = Constants.SEMICOLON_SPLIT_PATTERN.split(url);
if (us != null && us.length > 0) {
for (String u : us) {
URL url = URL.valueOf(u);
if (url.getPath() == null || url.getPath().length() == 0) {
url = url.setPath(interfaceName);
}
if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
urls.add(url.addParameterAndEncoded(Constants.REFER_KEY, StringUtils.toQueryString(map)));
} else {
urls.add(ClusterUtils.mergeUrl(url, map));
}
}
}
} else {
// assemble URL from register center's configuration
// 加載配置的所有注冊中心，拼裝成urls
List<URL> us = loadRegistries(false);
if (us != null && us.size() > 0) {
for (URL u : us) {
URL monitorUrl = loadMonitor(u);
if (monitorUrl != null) {
map.put(Constants.MONITOR_KEY, URL.encode(monitorUrl.toFullString()));
}
// 這部分其實把注冊中心和reference的信息進行了合并，后面的url是合并信息
urls.add(u.addParameterAndEncoded(Constants.REFER_KEY, StringUtils.toQueryString(map)));
}
}
}
// 根據(jù)注冊中心的數(shù)量選擇走分支，這里一般情況走if分支。
if (urls.size() == 1) {
// 單注冊中心或者直連的服務(wù)
invoker = refprotocol.refer(interfaceClass, urls.get(0));
} else {
// 多注冊中心，遍歷urls，調(diào)用refProtocol.refer創(chuàng)建遠程的動態(tài)代理Invoker
List<Invoker<?>> invokers = new ArrayList<Invoker<?>>();
URL registryURL = null;
// 多注冊中心用最后一個注冊中心的地址
for (URL url : urls) {
invokers.add(refprotocol.refer(interfaceClass, url));
if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
registryURL = url; // use last registry url
}
}
// 多注冊中心需要通過cluster選擇一個
if (registryURL != null) { // registry url is available
// use AvailableCluster only when register's cluster is available
URL u = registryURL.addParameter(Constants.CLUSTER_KEY, AvailableCluster.NAME);
invoker = cluster.join(new StaticDirectory(u, invokers));
} else { // not a registry url
invoker = cluster.join(new StaticDirectory(invokers));
}
}
}
// 創(chuàng)建一個代理
return (T) proxyFactory.getProxy(invoker);
}
}
dubbo 服務(wù)引用過程 - 階段二
說明：
1、RegistryProtocol內(nèi)部的doRefer()方法執(zhí)行consumer注冊和provider的訂閱。
2、registry.register()負責(zé)注冊consumer到zookeeper的對應(yīng)節(jié)點路徑上。
3、directory.subscribe()負責(zé)訂閱provider/configurator/routers等節(jié)點路徑信息。
public class RegistryProtocol implements Protocol {
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
// 從url的registryKey獲取注冊中心類型：zookeeper
url = url.setProtocol(url.getParameter(Constants.REGISTRY_KEY, Constants.DEFAULT_REGISTRY)).removeParameter(Constants.REGISTRY_KEY);
// 從RegistryFactory獲取注冊器
Registry registry = registryFactory.getRegistry(url);
if (RegistryService.class.equals(type)) {
return proxyFactory.getInvoker((T) registry, type, url);
}
// 省略相關(guān)代碼
// 關(guān)注走doRefer這部分邏輯
return doRefer(cluster, registry, type, url);
}
private <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
// 構(gòu)建RegistryDirectory,可以把它理解為注冊資源,其中包含了消費者/服務(wù)/路由等相關(guān)信息，其同時也是回調(diào)監(jiān)聽器
RegistryDirectory<T> directory = new RegistryDirectory<T>(type, url);
directory.setRegistry(registry);
directory.setProtocol(protocol);
// all attributes of REFER_KEY
Map<String, String> parameters = new HashMap<String, String>(directory.getUrl().getParameters());
// 構(gòu)建subscribeUrl信息，主要拼接consumer:xxx的url地址
URL subscribeUrl = new URL(Constants.CONSUMER_PROTOCOL, parameters.remove(Constants.REGISTER_IP_KEY), 0, type.getName(), parameters);
if (!Constants.ANY_VALUE.equals(url.getServiceInterface())
&& url.getParameter(Constants.REGISTER_KEY, true)) {
// 向注冊中心注冊服務(wù)消費者
registry.register(subscribeUrl.addParameters(Constants.CATEGORY_KEY, Constants.CONSUMERS_CATEGORY,
Constants.CHECK_KEY, String.valueOf(false)));
}
// 從注冊中心訂閱服務(wù)提供者（即引用的服務(wù)）
directory.subscribe(subscribeUrl.addParameter(Constants.CATEGORY_KEY,
Constants.PROVIDERS_CATEGORY
+ "," + Constants.CONFIGURATORS_CATEGORY
+ "," + Constants.ROUTERS_CATEGORY));
// 從invoker當(dāng)中選擇其中一個返回
Invoker invoker = cluster.join(directory);
// 注冊消費者
ProviderConsumerRegTable.registerConsuemr(invoker, url, subscribeUrl, directory);
return invoker;
}
}
dubbo 服務(wù)引用過程 - 階段三
說明：
1、ZookeeperRegistry的實現(xiàn)consumer的對應(yīng)的節(jié)點的注冊。
2、zkClient.create(toUrlPath(url))負責(zé)創(chuàng)建zookeeper節(jié)點信息。
public abstract class AbstractRegistry implements Registry {
public void register(URL url) {
registered.add(url);
}
}
public abstract class FailbackRegistry extends AbstractRegistry {
public void register(URL url) {
if (destroyed.get()){
return;
}
super.register(url);
failedRegistered.remove(url);
failedUnregistered.remove(url);
try {
// 注冊zookeeper節(jié)點上
doRegister(url);
} catch (Exception e) {
// 省略相關(guān)代碼
}
}
protected abstract void doRegister(URL url);
}
public class ZookeeperRegistry extends FailbackRegistry {
protected void doRegister(URL url) {
try {
zkClient.create(toUrlPath(url), url.getParameter(Constants.DYNAMIC_KEY, true));
} catch (Throwable e) {
// 省略相關(guān)代碼
}
}
}
dubbo 服務(wù)引用過程 - 階段四
說明：
1、RegistryDirectory完成consumer對provider端的zk節(jié)點的訂閱及回調(diào)處理。
2、RegistryDirectory的subscribe()方法調(diào)用FailbackRegistry.subscribe()方法。
3、FailbackRegistry.subscribe()內(nèi)部調(diào)用ZookeeperRegistry.doSubscribe()方法。
4、ZookeeperRegistry.doSubscribe()方法內(nèi)部遍歷以下目錄挨個進行訂閱。
/dubbo/com.alibaba.dubbo.demo.DemoService/providers
/dubbo/com.alibaba.dubbo.demo.DemoService/configurators
/dubbo/com.alibaba.dubbo.demo.DemoService/routers5、new ChildListener()負責(zé)創(chuàng)建zk監(jiān)聽的回調(diào)函數(shù)，內(nèi)部childChanged負責(zé)執(zhí)行notify回調(diào)。
6、zkClient.addChildListener()負責(zé)獲取path下所有節(jié)點信息，如providers目錄下所有的provider的列表，即provider的URL。
7、FailbackRegistry.notify()方法用于針對providers/configurators/routers目錄下的urls進行回調(diào)操作，用于初始化對應(yīng)的類似invoker操作。
8、childChanged()方法內(nèi)部的ZookeeperRegistry.this.notify()方法執(zhí)行監(jiān)聽節(jié)點變化并進行重新初始化。
9、 FailbackRegistry.notify()內(nèi)部調(diào)用listener.notify()回調(diào)RegistryDirectory.notify()方法，listener指代RegistryDirectory對象實例。
public class RegistryDirectory<T> extends AbstractDirectory<T> implements NotifyListener {
public void subscribe(URL url) {
//todo 關(guān)心這個對象的notify回調(diào)函數(shù)
setConsumerUrl(url);
registry.subscribe(url, this);
}
}
public abstract class FailbackRegistry extends AbstractRegistry {
public void subscribe(URL url, NotifyListener listener) {
if (destroyed.get()){
return;
}
super.subscribe(url, listener);
removeFailedSubscribed(url, listener);
try {
// Sending a subscription request to the server side
doSubscribe(url, listener);
} catch (Exception e) {
// 省略相關(guān)代碼
}
}
protected abstract void doSubscribe(URL url, NotifyListener listener);
}
public class ZookeeperRegistry extends FailbackRegistry {
protected void doSubscribe(final URL url, final NotifyListener listener) {
try {
if (Constants.ANY_VALUE.equals(url.getServiceInterface())) {
// 省略相關(guān)代碼
} else {
List<URL> urls = new ArrayList<URL>();
// path可以取以下的值
// /dubbo/com.alibaba.dubbo.demo.DemoService/providers
// /dubbo/com.alibaba.dubbo.demo.DemoService/configurators
// /dubbo/com.alibaba.dubbo.demo.DemoService/routers
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) {
// 內(nèi)部類訪問外部類ZookeeperRegistry實例調(diào)用回調(diào)notify方法
ZookeeperRegistry.this.notify(url, listener, toUrlsWithEmpty(url, parentPath, currentChilds));
}
});
zkListener = listeners.get(listener);
}
zkClient.create(path, false);
// 獲取path下的所有子節(jié)點并監(jiān)聽path路徑
List<String> children = zkClient.addChildListener(path, zkListener);
if (children != null) {
// 根據(jù)獲取path路徑下的子節(jié)點名稱，就是provider的URL路徑
urls.addAll(toUrlsWithEmpty(url, path, children));
}
}
// 通過回調(diào)將consumer:xxx的url路徑及對應(yīng)的
// providers/configurators/routers的路徑進行回調(diào)
notify(url, listener, urls);
}
} catch (Throwable e) {
// 省略相關(guān)代碼
}
}
}
public abstract class FailbackRegistry extends 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");
}
try {
doNotify(url, listener, urls);
} catch (Exception t) {
// 省略相關(guān)代碼
}
}
protected void doNotify(URL url, NotifyListener listener, List<URL> urls) {
super.notify(url, listener, urls);
}
}
public abstract class AbstractRegistry implements Registry {
protected void notify(URL url, NotifyListener listener, List<URL> 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);
}
// 遍歷providers/configurators/routers目錄下的所有url進行回調(diào)處理
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是RegistryDirectory對象
listener.notify(categoryList);
}
}
}
dubbo 服務(wù)引用過程 - 階段五
說明：
1、RegistryDirectory.notify()方法調(diào)用refreshInvoker(invokerUrls)實現(xiàn)invoker的創(chuàng)建。
2、refreshInvoker()方法內(nèi)部執(zhí)行兩個動作，分別創(chuàng)建新增的provider的invoker并下線刪除的provider的invoker。
3、toInvokers()內(nèi)部通過protocol.refer()方法創(chuàng)建provider的引用的invoker。
4、destroyUnusedInvokers()內(nèi)部負責(zé)清理下線的provider的invoker。
public class RegistryDirectory<T> extends AbstractDirectory<T> implements NotifyListener {
public synchronized void notify(List<URL> urls) {
//todo step1 根據(jù)類別將urls分類
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());
}
}
// configurators
if (configuratorUrls != null && configuratorUrls.size() > 0) {
this.configurators = toConfigurators(configuratorUrls);
}
// routers
if (routerUrls != null && routerUrls.size() > 0) {
List<Router> routers = toRouters(routerUrls);
if (routers != null) { // null - do nothing
setRouters(routers);
}
}
List<Configurator> localConfigurators = this.configurators; // local reference
// merge override parameters
this.overrideDirectoryUrl = directoryUrl;
if (localConfigurators != null && localConfigurators.size() > 0) {
for (Configurator configurator : localConfigurators) {
this.overrideDirectoryUrl = configurator.configure(overrideDirectoryUrl);
}
}
// todo providers 內(nèi)部的protocol.refer根據(jù)url創(chuàng)建遠程代理Invoker
refreshInvoker(invokerUrls);
}
private void refreshInvoker(List<URL> invokerUrls) {
if (invokerUrls != null && invokerUrls.size() == 1 && invokerUrls.get(0) != null
&& Constants.EMPTY_PROTOCOL.equals(invokerUrls.get(0).getProtocol())) {
// 省略相關(guān)代碼
} else {
this.forbidden = false; // Allow to access
Map<String, Invoker<T>> oldUrlInvokerMap = this.urlInvokerMap; // local reference
if (invokerUrls.size() == 0 && this.cachedInvokerUrls != null) {
invokerUrls.addAll(this.cachedInvokerUrls);
} else {
this.cachedInvokerUrls = new HashSet<URL>();
this.cachedInvokerUrls.addAll(invokerUrls);//Cached invoker urls, convenient for comparison
}
if (invokerUrls.size() == 0) {
return;
}
//todo 根據(jù)url創(chuàng)建遠程代理Invoker
Map<String, Invoker<T>> newUrlInvokerMap = toInvokers(invokerUrls);// Translate url list to Invoker map
Map<String, List<Invoker<T>>> newMethodInvokerMap = toMethodInvokers(newUrlInvokerMap); // Change method name to map Invoker Map
// state change
// If the calculation is wrong, it is not processed.
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;
}
this.methodInvokerMap = multiGroup ? toMergeMethodInvokerMap(newMethodInvokerMap) : newMethodInvokerMap;
this.urlInvokerMap = newUrlInvokerMap;
try {
destroyUnusedInvokers(oldUrlInvokerMap, newUrlInvokerMap); // Close the unused Invoker
} catch (Exception e) {
logger.warn("destroyUnusedInvokers error. ", e);
}
}
}
private Map<String, Invoker<T>> toInvokers(List<URL> urls) {
Map<String, Invoker<T>> newUrlInvokerMap = new HashMap<String, Invoker<T>>();
String key = url.toFullString(); // The parameter urls are sorted
if (keys.contains(key)) { // Repeated url
continue;
}
keys.add(key);
// Cache key is url that does not merge with consumer side parameters, regardless of how the consumer combines parameters, if the server url changes, then refer again
Map<String, Invoker<T>> localUrlInvokerMap = this.urlInvokerMap; // local reference
Invoker<T> invoker = localUrlInvokerMap == null ? null : localUrlInvokerMap.get(key);
if (invoker == null) { // Not in the cache, refer again
try {
// protocol.refer進行invoker創(chuàng)建的流程，待后續(xù)進行分析。
if (enabled) {
invoker = new InvokerDelegate<T>(protocol.refer(serviceType, url), url, providerUrl);
}
} catch (Throwable t) {
}
if (invoker != null) { // Put new invoker in cache
newUrlInvokerMap.put(key, invoker);
}
} else {
newUrlInvokerMap.put(key, invoker);
}
}
keys.clear();
return newUrlInvokerMap;
}
private void destroyUnusedInvokers(Map<String, Invoker<T>> oldUrlInvokerMap, Map<String, Invoker<T>> newUrlInvokerMap) {
if (newUrlInvokerMap == null || newUrlInvokerMap.size() == 0) {
destroyAllInvokers();
return;
}
// check deleted invoker
List<String> deleted = null;
if (oldUrlInvokerMap != null) {
Collection<Invoker<T>> newInvokers = newUrlInvokerMap.values();
for (Map.Entry<String, Invoker<T>> entry : oldUrlInvokerMap.entrySet()) {
if (!newInvokers.contains(entry.getValue())) {
if (deleted == null) {
deleted = new ArrayList<String>();
}
deleted.add(entry.getKey());
}
}
}
if (deleted != null) {
for (String url : deleted) {
if (url != null) {
Invoker<T> invoker = oldUrlInvokerMap.remove(url);
if (invoker != null) {
try {
invoker.destroy();
if (logger.isDebugEnabled()) {
logger.debug("destory invoker[" + invoker.getUrl() + "] success. ");
}
} catch (Exception e) {
logger.warn("destory invoker[" + invoker.getUrl() + "] faild. " + e.getMessage(), e);
}
}
}
}
}
}
}
dubbo 服務(wù)引用過程 - 階段六
說明：
- 1、consumer端的RegistryDirectory維持了provider的invoker信息。
public class RegistryDirectory<T> extends AbstractDirectory<T> implements NotifyListener {
private static final Logger logger = LoggerFactory.getLogger(RegistryDirectory.class);
private static final Cluster cluster = ExtensionLoader.getExtensionLoader(Cluster.class).getAdaptiveExtension();
private static final RouterFactory routerFactory = ExtensionLoader.getExtensionLoader(RouterFactory.class).getAdaptiveExtension();
private static final ConfiguratorFactory configuratorFactory = ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class).getAdaptiveExtension();
private final String serviceKey; // Initialization at construction time, assertion not null
private final Class<T> serviceType; // Initialization at construction time, assertion not null
private final Map<String, String> queryMap; // Initialization at construction time, assertion not null
private final URL directoryUrl; // Initialization at construction time, assertion not null, and always assign non null value
private final String[] serviceMethods;
private final boolean multiGroup;
private Protocol protocol; // Initialization at the time of injection, the assertion is not null
private Registry registry; // Initialization at the time of injection, the assertion is not null
private volatile boolean forbidden = false;
private volatile URL overrideDirectoryUrl; // Initialization at construction time, assertion not null, and always assign non null value
/**
* override rules
* Priority: override>-D>consumer>provider
* Rule one: for a certain provider <ip:port,timeout=100>
* Rule two: for all providers <* ,timeout=5000>
*/
private volatile List<Configurator> configurators; // The initial value is null and the midway may be assigned to null, please use the local variable reference
// Map<url, Invoker> cache service url to invoker mapping.
private volatile Map<String, Invoker<T>> urlInvokerMap; // The initial value is null and the midway may be assigned to null, please use the local variable reference
// Map<methodName, Invoker> cache service method to invokers mapping.
private volatile Map<String, List<Invoker<T>>> methodInvokerMap; // The initial value is null and the midway may be assigned to null, please use the local variable reference
// Set<invokerUrls> cache invokeUrls to invokers mapping.
private volatile Set<URL> cachedInvokerUrls; // The initial value is null and the midway may be assigned to null, please use the local variable reference
}
