Dubbo中消费者初始化的过程解析

首先还是Spring碰到dubbo的标签之后,会使用parseCustomElement解析dubbo标签,使用的解析器是dubbo的DubboBeanDefinitionParser,解析完成之后返回BeanDefinition给Spring管理。

服务消费者端对应的是ReferenceBean,实现了ApplicationContextAware接口,Spring会在Bean的实例化那一步回调setApplicationContext方法。也实现了InitializingBean接口,接着会回调afterPropertySet方法。还实现了FactoryBean接口,实现FactoryBean可以在后期获取bean的时候做一些操作,dubbo在这个时候做初始化。另外ReferenceBean还实现了DisposableBean,会在bean销毁的时候调用destory方法。

消费者的初始化是在ReferenceBean的init方法中执行,分为两种情况:

  • reference标签中没有配置init属性,此时是延迟初始化的,也就是只有等到bean引用被注入到其他Bean中,或者调用getBean获取这个Bean的时候,才会初始化。比如在这里的例子里reference没有配置init属性,只有等到HelloService helloService = (HelloService) applicationContext.getBean("helloService");这句getBean的时候,才会开始调用init方法进行初始化。
  • 另外一种情况是立即初始化,即是如果reference标签中init属性配置为true,会立即进行初始化(也就是上面说到的实现了FactoryBean接口)。

初始化开始

这里以没有配置init的reference为例,只要不注入bean或者不调用getBean获取bean的时候,就不会被初始化。HelloService helloService = (HelloService) applicationContext.getBean("helloService");

另外在ReferenceBean这个类在Spring中初始化的时候,有几个静态变量会被初始化:

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private static final Protocol refprotocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();

private static final Cluster cluster = ExtensionLoader.getExtensionLoader(Cluster.class).getAdaptiveExtension();

private static final ProxyFactory proxyFactory = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();

这几个变量的初始化是根据dubbo的SPI扩展机制动态生成的代码:

refprotocol:

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import com.alibaba.dubbo.common.extension.ExtensionLoader;
public class Protocol$Adpative implements com.alibaba.dubbo.rpc.Protocol {
public com.alibaba.dubbo.rpc.Invoker refer(java.lang.Class arg0, com.alibaba.dubbo.common.URL arg1) throws java.lang.Class {
if (arg1 == null) throw new IllegalArgumentException("url == null");

com.alibaba.dubbo.common.URL url = arg1;
String extName = ( url.getProtocol() == null ? "dubbo" : url.getProtocol() );

if(extName == null) throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.Protocol) name from url(" + url.toString() + ") use keys([protocol])");

com.alibaba.dubbo.rpc.Protocol extension = (com.alibaba.dubbo.rpc.Protocol)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.Protocol.class).getExtension(extName);

return extension.refer(arg0, arg1);
}

public com.alibaba.dubbo.rpc.Exporter export(com.alibaba.dubbo.rpc.Invoker arg0) throws com.alibaba.dubbo.rpc.Invoker {
if (arg0 == null) throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument == null");

if (arg0.getUrl() == null) throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument getUrl() == null");com.alibaba.dubbo.common.URL url = arg0.getUrl();

String extName = ( url.getProtocol() == null ? "dubbo" : url.getProtocol() );

if(extName == null) throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.Protocol) name from url(" + url.toString() + ") use keys([protocol])");

com.alibaba.dubbo.rpc.Protocol extension = (com.alibaba.dubbo.rpc.Protocol)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.Protocol.class).getExtension(extName);

return extension.export(arg0);
}

public void destroy() {
throw new UnsupportedOperationException("method public abstract void com.alibaba.dubbo.rpc.Protocol.destroy() of interface com.alibaba.dubbo.rpc.Protocol is not adaptive method!");
}

public int getDefaultPort() {
throw new UnsupportedOperationException("method public abstract int com.alibaba.dubbo.rpc.Protocol.getDefaultPort() of interface com.alibaba.dubbo.rpc.Protocol is not adaptive method!");
}
}

cluster:

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import com.alibaba.dubbo.common.extension.ExtensionLoader;
public class Cluster$Adpative implements com.alibaba.dubbo.rpc.cluster.Cluster {

public com.alibaba.dubbo.rpc.Invoker join(com.alibaba.dubbo.rpc.cluster.Directory arg0) throws com.alibaba.dubbo.rpc.cluster.Directory {
if (arg0 == null) throw new IllegalArgumentException("com.alibaba.dubbo.rpc.cluster.Directory argument == null");

if (arg0.getUrl() == null) throw new IllegalArgumentException("com.alibaba.dubbo.rpc.cluster.Directory argument getUrl() == null");com.alibaba.dubbo.common.URL url = arg0.getUrl();

String extName = url.getParameter("cluster", "failover");
if(extName == null) throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.cluster.Cluster) name from url(" + url.toString() + ") use keys([cluster])");

com.alibaba.dubbo.rpc.cluster.Cluster extension = (com.alibaba.dubbo.rpc.cluster.Cluster)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.cluster.Cluster.class).getExtension(extName);

return extension.join(arg0);
}
}

proxyFactory:

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import com.alibaba.dubbo.common.extension.ExtensionLoader;
public class ProxyFactory$Adpative implements com.alibaba.dubbo.rpc.ProxyFactory {

public java.lang.Object getProxy(com.alibaba.dubbo.rpc.Invoker arg0) throws com.alibaba.dubbo.rpc.Invoker {
if (arg0 == null) throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument == null");

if (arg0.getUrl() == null) throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument getUrl() == null");com.alibaba.dubbo.common.URL url = arg0.getUrl();

String extName = url.getParameter("proxy", "javassist");
if(extName == null) throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.ProxyFactory) name from url(" + url.toString() + ") use keys([proxy])");

com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);

return extension.getProxy(arg0);
}

public com.alibaba.dubbo.rpc.Invoker getInvoker(java.lang.Object arg0, java.lang.Class arg1, com.alibaba.dubbo.common.URL arg2) throws java.lang.Object {
if (arg2 == null) throw new IllegalArgumentException("url == null");

com.alibaba.dubbo.common.URL url = arg2;
String extName = url.getParameter("proxy", "javassist");

if(extName == null) throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.ProxyFactory) name from url(" + url.toString() + ") use keys([proxy])");

com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);

return extension.getInvoker(arg0, arg1, arg2);
}
}

初始化入口

初始化的入口在ReferenceConfig的get()方法:

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public synchronized T get() {
if (destroyed){
throw new IllegalStateException("Already destroyed!");
}
if (ref == null) {
init();
}
return ref;
}

init()方法会先检查初始化所有的配置信息,然后调用ref = createProxy(map);创建代理,消费者最终得到的是服务的代理。初始化主要做的事情就是引用对应的远程服务,大概的步骤:

  • 监听注册中心
  • 连接服务提供者端进行服务引用
  • 创建服务代理并返回

文档上关于Zookeeper作为注册中心时,服务消费者启动时要做的事情有:

订阅/dubbo/com.foo.BarService/providers目录下的提供者URL地址。
并向/dubbo/com.foo.BarService/consumers目录下写入自己的URL地址。

创建代理

  • 引用远程服务
  • 创建代理

init()中createProxy方法:

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private T createProxy(Map<String, String> map) {
//先判断是否是本地服务引用injvm
//判断是否是点对点直连
//判断是否是通过注册中心连接
//然后是服务的引用
//这里url为
//registry://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?
//application=dubbo-consumer&dubbo=2.5.3&pid=12272&
//refer=application%3Ddubbo-consumer%26dubbo%3D2.5.3%26
//interface%3Ddubbo.common.hello.service.HelloService%26
//methods%3DsayHello%26pid%3D12272%26side%3D
//consumer%26timeout%3D100000%26timestamp%3D1489318676447&
//registry=zookeeper&timestamp=1489318676641
//引用远程服务由Protocol的实现来处理
refprotocol.refer(interfaceClass, url);
//最后返回服务代理
return (T) proxyFactory.getProxy(invoker);
}

这里refprotocol是上面生成的代码,会根据协议不同选择不同的Protocol协议。

引用远程服务

对于服务引用refprotocol.refer(interfaceClass, url)会首先进入ProtocolListenerWrapper的refer方法,然后在进入ProtocolFilterWrapper的refer方法,然后再进入RegistryProtocol的refer方法,这里的url协议是registry,所以上面两个Wrapper中不做处理,直接进入了RegistryProtocol,看下RegistryProtocol中:

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public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
//这里获得的url是
//zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?
//application=dubbo-consumer&dubbo=2.5.3&pid=12272&
//refer=application%3Ddubbo-consumer%26dubbo%3D2.5.3%26
//interface%3Ddubbo.common.hello.service.HelloService%26
//methods%3DsayHello%26pid%3D12272%26side%3D
//consumer%26timeout%3D100000%26
//timestamp%3D1489318676447&timestamp=1489318676641
url = url.setProtocol(url.getParameter(Constants.REGISTRY_KEY, Constants.DEFAULT_REGISTRY)).removeParameter(Constants.REGISTRY_KEY);
//根据url获取Registry对象
//先连接注册中心,把消费者注册到注册中心
Registry registry = registryFactory.getRegistry(url);
//判断引用是否是注册中心RegistryService,如果是直接返回刚得到的注册中心服务
if (RegistryService.class.equals(type)) {
return proxyFactory.getInvoker((T) registry, type, url);
}
//以下是普通服务,需要进入注册中心和集群下面的逻辑
// group="a,b" or group="*"
//获取ref的各种属性
Map<String, String> qs = StringUtils.parseQueryString(url.getParameterAndDecoded(Constants.REFER_KEY));
//获取分组属性
String group = qs.get(Constants.GROUP_KEY);
//先判断引用服务是否需要合并不同实现的返回结果
if (group != null && group.length() > 0 ) {
if ( ( Constants.COMMA_SPLIT_PATTERN.split( group ) ).length > 1
|| "*".equals( group ) ) {
//使用默认的分组聚合集群策略
return doRefer( getMergeableCluster(), registry, type, url );
}
}
//选择配置的集群策略(cluster="failback")或者默认策略
return doRefer(cluster, registry, type, url);
}

获取注册中心

连接注册中心Registry registry = registryFactory.getRegistry(url);首先会到AbstractRegistryFactory的getRegistry方法:

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public Registry getRegistry(URL url) {
//这里url是
//zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?
//application=dubbo-consumer&dubbo=2.5.3&
//interface=com.alibaba.dubbo.registry.RegistryService&
//pid=12272&timestamp=1489318676641
url = url.setPath(RegistryService.class.getName())
.addParameter(Constants.INTERFACE_KEY, RegistryService.class.getName())
.removeParameters(Constants.EXPORT_KEY, Constants.REFER_KEY);
//这里key是
//zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService
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;
}
//这里用的是ZookeeperRegistryFactory
//返回的Registry中封装了已经连接到Zookeeper的zkClient实例
registry = createRegistry(url);
if (registry == null) {
throw new IllegalStateException("Can not create registry " + url);
}
//放到缓存中
REGISTRIES.put(key, registry);
return registry;
} finally {
// 释放锁
LOCK.unlock();
}
}

ZookeeperRegistryFactory的createRegistry方法:

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public Registry createRegistry(URL url) {
//直接返回一个新的ZookeeperRegistry实例
//这里的zookeeperTransporter代码在下面,动态生成的适配类
return new ZookeeperRegistry(url, zookeeperTransporter);
}

zookeeperTransporter代码:

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package com.alibaba.dubbo.remoting.zookeeper;
import com.alibaba.dubbo.common.extension.ExtensionLoader;
public class ZookeeperTransporter$Adpative implements com.alibaba.dubbo.remoting.zookeeper.ZookeeperTransporter {
public com.alibaba.dubbo.remoting.zookeeper.ZookeeperClient connect(com.alibaba.dubbo.common.URL arg0) {
if (arg0 == null) throw new IllegalArgumentException("url == null");

com.alibaba.dubbo.common.URL url = arg0;
String extName = url.getParameter("client", url.getParameter("transporter", "zkclient"));

if(extName == null) throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.remoting.zookeeper.ZookeeperTransporter) name from url(" + url.toString() + ") use keys([client, transporter])");

com.alibaba.dubbo.remoting.zookeeper.ZookeeperTransporter extension = (com.alibaba.dubbo.remoting.zookeeper.ZookeeperTransporter)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.remoting.zookeeper.ZookeeperTransporter.class).getExtension(extName);

return extension.connect(arg0);
}
}

上面代码中可以看到,如果我们没有指定Zookeeper的client属性,默认使用zkClient,所以上面的zookeeperTransporter是ZkclientZookeeperTransporter。

继续看new ZookeeperRegistry(url, zookeeperTransporter);

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public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) {
//这里会先经过AbstractRegistry的处理,然后经过FailbackRegistry的处理(解释在下面)
super(url);
if (url.isAnyHost()) {
throw new IllegalStateException("registry address == null");
}
//服务分组,默认dubbo
String group = url.getParameter(Constants.GROUP_KEY, DEFAULT_ROOT);
if (! group.startsWith(Constants.PATH_SEPARATOR)) {
group = Constants.PATH_SEPARATOR + group;
}
//注册中心的节点
this.root = group;
//ZkclientZookeeperTransporter的connect方法
//直接返回一个ZkclientZookeeperClient实例
//具体的步骤是,new一个ZkClient实例,然后订阅了一个状态变化的监听器
zkClient = zookeeperTransporter.connect(url);
//添加一个状态改变的监听器
zkClient.addStateListener(new StateListener() {
public void stateChanged(int state) {
if (state == RECONNECTED) {
try {
recover();
} catch (Exception e) {
logger.error(e.getMessage(), e);
}
}
}
});
}

AbstractRegistry的处理:

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public AbstractRegistry(URL url) {
//设置registryUrl
setUrl(url);
// 启动文件保存定时器
syncSaveFile = url.getParameter(Constants.REGISTRY_FILESAVE_SYNC_KEY, false);
//会先去用户主目录下的.dubbo目录下加载缓存注册中心的缓存文件比如:dubbo-registry-127.0.0.1.cache
String filename = url.getParameter(Constants.FILE_KEY, System.getProperty("user.home") + "/.dubbo/dubbo-registry-" + url.getHost() + ".cache");
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;
//缓存文件存在的话就把文件读进内存中
loadProperties();
//先获取backup url
//然后通知订阅
notify(url.getBackupUrls());
}

获取注册中心时的通知方法

notify方法:

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protected void notify(List<URL> urls) {
if(urls == null || urls.isEmpty()) return;
//getSubscribed()方法获取订阅者列表
for (Map.Entry<URL, Set<NotifyListener>> entry : getSubscribed().entrySet()) {
URL url = entry.getKey();

if(! UrlUtils.isMatch(url, urls.get(0))) {
continue;
}

Set<NotifyListener> listeners = entry.getValue();
if (listeners != null) {
for (NotifyListener listener : listeners) {
try {
//通知每个监听器
notify(url, listener, filterEmpty(url, urls));
} catch (Throwable t) { }
}
}
}
}

notify(url, listener, filterEmpty(url, urls));代码:

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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)) {
//分类
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);
//通知
listener.notify(categoryList);
}
}

AbstractRegistry构造完,接着是FailbackRegistry的处理:

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public FailbackRegistry(URL url) {
super(url);
int retryPeriod = url.getParameter(Constants.REGISTRY_RETRY_PERIOD_KEY, Constants.DEFAULT_REGISTRY_RETRY_PERIOD);
//启动失败重试定时器
this.retryFuture = retryExecutor.scheduleWithFixedDelay(new Runnable() {
public void run() {
// 检测并连接注册中心
try {
//重试方法由每个具体子类实现
//获取到注册失败的,然后尝试注册
retry();
} catch (Throwable t) { // 防御性容错 }
}
}, retryPeriod, retryPeriod, TimeUnit.MILLISECONDS);
}

这里会启动一个新的定时线程,主要是有连接失败的话,会进行重试连接retry(),启动完之后返回ZookeeperRegistry中继续处理。接下来下一步是服务的引用。

引用远程服务

继续看ref方法中最后一步,服务的引用,返回的是一个Invoker,return doRefer(cluster, registry, type, url);

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private <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
//初始化Directory
//组装Directory,可以看成一个消费端的List,可以随着注册中心的消息推送而动态的变化服务的Invoker
//封装了所有服务真正引用逻辑,覆盖配置,路由规则等逻辑
//初始化时只需要向注册中心发起订阅请求,其他逻辑均是异步处理,包括服务的引用等
//缓存接口所有的提供者端Invoker以及注册中心接口相关的配置等
RegistryDirectory<T> directory = new RegistryDirectory<T>(type, url);
directory.setRegistry(registry);
directory.setProtocol(protocol);
//此处的subscribeUrl为
//consumer://192.168.1.100/dubbo.common.hello.service.HelloService?
//application=dubbo-consumer&dubbo=2.5.3&
//interface=dubbo.common.hello.service.HelloService&
//methods=sayHello&pid=16409&
//side=consumer&timeout=100000&timestamp=1489322133987
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)) {
//到注册中心注册服务
//此处regist是上面一步获得的registry,即是ZookeeperRegistry,包含zkClient的实例
//会先经过AbstractRegistry的处理,然后经过FailbackRegistry的处理(解析在下面)
registry.register(subscribeUrl.addParameters(Constants.CATEGORY_KEY, Constants.CONSUMERS_CATEGORY,
Constants.CHECK_KEY, String.valueOf(false)));
}
//订阅服务
//有服务提供的时候,注册中心会推送服务消息给消费者,消费者再进行服务的引用。
directory.subscribe(subscribeUrl.addParameter(Constants.CATEGORY_KEY,
Constants.PROVIDERS_CATEGORY
+ "," + Constants.CONFIGURATORS_CATEGORY
+ "," + Constants.ROUTERS_CATEGORY));
//服务的引用与变更全部由Directory异步完成
//集群策略会将Directory伪装成一个Invoker返回
//合并所有相同的invoker
return cluster.join(directory);
}

注册中心接收到消费者发送的订阅请求后,会根据提供者注册服务的列表,推送服务消息给消费者。消费者端接收到注册中心发来的提供者列表后,进行服务的引用。触发Directory监听器的可以是订阅请求,覆盖策略消息,路由策略消息。

注册到注册中心

AbstractRegistry的register方法:

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public void register(URL url) {
//此时url是
//consumer://192.168.1.100/dubbo.common.hello.service.HelloService?
//application=dubbo-consumer&
//category=consumers&check=false&dubbo=2.5.3&
//interface=dubbo.common.hello.service.HelloService&methods=sayHello
//&pid=16409&side=consumer&timeout=100000&timestamp=1489322133987
if (url == null) {
throw new IllegalArgumentException("register url == null");
}
if (logger.isInfoEnabled()){
logger.info("Register: " + url);
}
registered.add(url);
}

上面只是把url添加到registered这个set中。

接着看FailbackRegistry的register方法:

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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
//这里调用的是ZookeeperRegistry中的doRegister方法
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);
}
}

接着看下doRegister(url);方法,向服务器端发送注册请求,在ZookeeperRegistry中:

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protected void doRegister(URL url) {
try {
//直接调用create,在AbstractZookeeperClient类中
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);
}
}

zkClient.create()方法:

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//path为
///dubbo/dubbo.common.hello.service.HelloService/consumers/
//consumer%3A%2F%2F192.168.1.100%2F
//dubbo.common.hello.service.HelloService%3Fapplication%3D
//dubbo-consumer%26category%3Dconsumers%26check%3Dfalse%26
//dubbo%3D2.5.3%26interface%3D
//dubbo.common.hello.service.HelloService%26
//methods%3DsayHello%26pid%3D28819%26
//side%3Dconsumer%26timeout%3D100000%26timestamp%3D1489332839677
public void create(String path, boolean ephemeral) {
int i = path.lastIndexOf('/');
if (i > 0) {
create(path.substring(0, i), false);
}
//循环完得到的path为/dubbo
//dynamic=false 表示该数据为持久数据,当注册方退出时,数据依然保存在注册中心
if (ephemeral) {
//创建临时的节点
createEphemeral(path);
} else {
//创建持久的节点,/dubbo/dubbo.common.hello.service.HelloService/consumers/
//consumer%3A%2F%2F192.168.110.197%2F
//dubbo.common.hello.service.HelloService%3Fapplication%3Ddubbo-consumer%26
//category%3Dconsumers%26check%3Dfalse%26
//dubbo%3D2.5.3%26interface%3D
//dubbo.common.hello.service.HelloService%26
//methods%3DsayHello%26pid%3D6370%26side%3D
//consumer%26timeout%3D100000%26timestamp%3D1489367959659
createPersistent(path);
}
}

经过上面create之后,Zookeeper中就存在了消费者需要订阅的服务的节点:

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/dubbo
/dubbo.common.hello.service.HelloService
/consumers
/http://0.0.0.0:4550/?path=dubbo%2F
dubbo.common.hello.service.HelloService%2F
consumers%2Fconsumer%253A%252F%252F192.168.110.197%252F
dubbo.common.hello.service.HelloService%253F
application%253Ddubbo-consumer%2526category%253D
consumers%2526check%253Dfalse%2526
dubbo%253D2.5.3%2526interface%253D
dubbo.common.hello.service.HelloService%2526
methods%253DsayHello%2526pid%253D22392%2526side%253D
consumer%2526timeout%253D100000%2526timestamp%253D1490063394184

订阅服务提供者

消费者自己注册到注册中心之后,接着是订阅服务提供者,directory.subscribe():

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public void subscribe(URL url) {
//设置消费者url
setConsumerUrl(url);
//这里的registry是ZookeeperRegistry
registry.subscribe(url, this);
}

看下registry.subscribe(url, this);,这里registry是ZookeeperRegistry,会先经过AbstractRegistry的处理,然后是FailbackRegistry的处理。

在AbstractRegistry中:

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//此时url为consumer://192.168.1.100/dubbo.common.hello.service.HelloService?application=dubbo-consumer&
//category=providers,configurators,routers&dubbo=2.5.3&interface=dubbo.common.hello.service.HelloService&methods=
//sayHello&pid=28819&side=consumer&timeout=100000&timestamp=1489332839677
public void subscribe(URL url, NotifyListener listener) {
//先根据url获取已注册的监听器
Set<NotifyListener> listeners = subscribed.get(url);
//没有监听器,就创建,并添加进去
if (listeners == null) {
subscribed.putIfAbsent(url, new ConcurrentHashSet<NotifyListener>());
listeners = subscribed.get(url);
}
//有监听器,直接把当前RegistryDirectory添加进去
listeners.add(listener);
}

然后是FailbackRegistry中:

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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) {...}
}

继续看doSubscribe(url, listener);向服务端发送订阅请求,在ZookeeperRegistry中:

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protected void doSubscribe(final URL url, final NotifyListener listener) {
try {
if (Constants.ANY_VALUE.equals(url.getServiceInterface())) {... } 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);
}
//将zkClient的事件IZkChildListener转换到registry事件NotifyListener
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);
}
//创建三个节点
// /dubbo/dubbo.common.hello.service.HelloService/providers/
// /dubbo/dubbo.common.hello.service.HelloService/configurators/
// /dubbo/dubbo.common.hello.service.HelloService/routers/
//上面三个路径会被消费者端监听,当提供者,配置,路由发生变化之后,
//注册中心会通知消费者刷新本地缓存。
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);
}
}

服务订阅完之后的通知

服务订阅完成之后,接着就是notify(url, listener, urls);:

会先经过FailbackRegistry将失败的通知请求记录到失败列表,定时重试。

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

doNotify(url, listener, urls);:

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

AbstractRegistry中的doNotify实现:

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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)) {
//不同类型的数据分开通知,providers,consumers,routers,overrides
//允许只通知其中一种类型,但该类型的数据必须是全量的,不是增量的。
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);
}
//对这里得到的providers,configurators,routers分别进行通知
for (Map.Entry<String, List<URL>> entry : result.entrySet()) {
String category = entry.getKey();
List<URL> categoryList = entry.getValue();
categoryNotified.put(category, categoryList);
saveProperties(url);
//这里的listener是RegistryDirectory
listener.notify(categoryList);
}
}

到RegistryDirectory中查看notify方法:

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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());
}
}
// configurators 更新缓存的服务提供方配置
if (configuratorUrls != null && configuratorUrls.size() >0 ){
this.configurators = toConfigurators(configuratorUrls);
}
// routers//更新缓存的路由规则配置
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
// 合并override参数
this.overrideDirectoryUrl = directoryUrl;
if (localConfigurators != null && localConfigurators.size() > 0) {
for (Configurator configurator : localConfigurators) {
this.overrideDirectoryUrl = configurator.configure(overrideDirectoryUrl);
}
}
// providers
//重建invoker实例
refreshInvoker(invokerUrls);
}

重建invoker实例

refreshInvoker(invokerUrls);:

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/**
* 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
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.cachedInvokerUrls != null){
invokerUrls.addAll(this.cachedInvokerUrls);
} else {
this.cachedInvokerUrls = new HashSet<URL>();
this.cachedInvokerUrls.addAll(invokerUrls);//缓存invokerUrls列表,便于交叉对比
}
if (invokerUrls.size() ==0 ){
return;
}
//会重新走一遍服务的引用过程
//给每个提供者创建一个Invoker
Map<String, Invoker<T>> newUrlInvokerMap = toInvokers(invokerUrls) ;// 将URL列表转成Invoker列表
Map<String, List<Invoker<T>>> newMethodInvokerMap = toMethodInvokers(newUrlInvokerMap); // 换方法名映射Invoker列表
// state change
//如果计算错误,则不进行处理.
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 ;
}
//服务提供者Invoker保存在这个map中
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);
}
}
}

toInvokers(invokerUrls) 方法:

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private Map<String, Invoker<T>> toInvokers(List<URL> urls) {
Map<String, Invoker<T>> newUrlInvokerMap = new HashMap<String, Invoker<T>>();
if(urls == null || urls.size() == 0){
return newUrlInvokerMap;
}
Set<String> keys = new HashSet<String>();
String queryProtocols = this.queryMap.get(Constants.PROTOCOL_KEY);
for (URL providerUrl : urls) {
//此时url是dubbo://192.168.110.197:20880/dubbo.common.hello.service.HelloService?anyhost=true&
//application=dubbo-provider&application.version=1.0&dubbo=2.5.3&environment=product&
//interface=dubbo.common.hello.service.HelloService&methods=sayHello&organization=china&
//owner=cheng.xi&pid=5631&side=provider&timestamp=1489367571986
//从注册中心获取到的携带提供者信息的url
//如果reference端配置了protocol,则只选择匹配的protocol
if (queryProtocols != null && queryProtocols.length() >0) {
boolean accept = false;
String[] acceptProtocols = queryProtocols.split(",");
for (String acceptProtocol : acceptProtocols) {
if (providerUrl.getProtocol().equals(acceptProtocol)) {
accept = true;
break;
}
}
if (!accept) {
continue;
}
}
if (Constants.EMPTY_PROTOCOL.equals(providerUrl.getProtocol())) {
continue;
}
if (! ExtensionLoader.getExtensionLoader(Protocol.class).hasExtension(providerUrl.getProtocol())) {
logger.error(new IllegalStateException("Unsupported protocol " + providerUrl.getProtocol() + " in notified url: " + providerUrl + " from registry " + getUrl().getAddress() + " to consumer " + NetUtils.getLocalHost()
+ ", supported protocol: "+ExtensionLoader.getExtensionLoader(Protocol.class).getSupportedExtensions()));
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 {
boolean enabled = true;
if (url.hasParameter(Constants.DISABLED_KEY)) {
enabled = ! url.getParameter(Constants.DISABLED_KEY, false);
} else {
enabled = url.getParameter(Constants.ENABLED_KEY, true);
}
if (enabled) {
//根据扩展点加载机制,这里使用的protocol是DubboProtocol
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
newUrlInvokerMap.put(key, invoker);
}
}else {
newUrlInvokerMap.put(key, invoker);
}
}
keys.clear();
return newUrlInvokerMap;
}

创建invoker invoker = new InvokerDelegete<T>(protocol.refer(serviceType, url), url, providerUrl);

  • 先使用DubboProtocol的refer方法,这一步会依次调用ProtocolFIlterListenerWrapper,ProtocolFilterWrapper,DubboProtocol中的refer方法。经过两个Wrapper中,会添加对应的InvokerListener并构建Invoker Filter链,在DubboProtocol中会创建一个DubboInvoker对象,该Invoker对象持有服务Class,providerUrl,负责和服务提供端通信的ExchangeClient。
  • 接着使用得到的Invoker创建一个InvokerDelegete

创建invoker

在DubboProtocol中创建DubboInvoker的时候代码如下:

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public <T> Invoker<T> refer(Class<T> serviceType, URL url) throws RpcException {
// create rpc invoker.
//这里有一个getClients方法
DubboInvoker<T> invoker = new DubboInvoker<T>(serviceType, url, getClients(url), invokers);
invokers.add(invoker);
return invoker;
}

查看getClients方法:

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private ExchangeClient[] getClients(URL url){
//是否共享连接
boolean service_share_connect = false;
int connections = url.getParameter(Constants.CONNECTIONS_KEY, 0);
//如果connections不配置,则共享连接,否则每服务每连接
if (connections == 0){
service_share_connect = true;
connections = 1;
}

ExchangeClient[] clients = new ExchangeClient[connections];
for (int i = 0; i < clients.length; i++) {
if (service_share_connect){
//这里没有配置connections,就使用getSharedClient
//getSharedClient中先去缓存中查找,没有的话就会新建,也是调用initClient方法
clients[i] = getSharedClient(url);
} else {
clients[i] = initClient(url);
}
}
return clients;
}

直接看initClient方法:

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//创建新连接
private ExchangeClient initClient(URL url) {

// client type setting.
String str = url.getParameter(Constants.CLIENT_KEY, url.getParameter(Constants.SERVER_KEY, Constants.DEFAULT_REMOTING_CLIENT));

String version = url.getParameter(Constants.DUBBO_VERSION_KEY);
boolean compatible = (version != null && version.startsWith("1.0."));
url = url.addParameter(Constants.CODEC_KEY, Version.isCompatibleVersion() && compatible ? COMPATIBLE_CODEC_NAME : DubboCodec.NAME);
//默认开启heartbeat
url = url.addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT));

// BIO存在严重性能问题,暂时不允许使用
if (str != null && str.length() > 0 && ! ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {
throw new RpcException("Unsupported client type: " + str + "," +
" supported client type is " + StringUtils.join(ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions(), " "));
}

ExchangeClient client ;
try {
//如果lazy属性没有配置为true(我们没有配置,默认为false)ExchangeClient会马上和服务端建立连接
//设置连接应该是lazy的
if (url.getParameter(Constants.LAZY_CONNECT_KEY, false)){
client = new LazyConnectExchangeClient(url ,requestHandler);
} else {
//立即和服务端建立连接
client = Exchangers.connect(url ,requestHandler);
}
} catch (RemotingException e) {
throw new RpcException("Fail to create remoting client for service(" + url
+ "): " + e.getMessage(), e);
}
return client;
}

和服务端建立连接,Exchangers.connect(url ,requestHandler);,其实最后使用的是HeaderExchanger,Exchanger目前只有这一个实现:

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public ExchangeClient connect(URL url, ExchangeHandler handler) throws RemotingException {
//先经过HeaderExchangeHandler包装
//然后是DecodeHandler
//然后是Transporters.connect
//返回一个HeaderExchangerClient,这里封装了client,channel,启动心跳的定时器等
return new HeaderExchangeClient(Transporters.connect(url, new DecodeHandler(new HeaderExchangeHandler(handler))));
}

Transporters.connect中也是根据SPI扩展获取Transport的具体实现,这里默认使用NettyTransporter.connect(),在NettyTransporter的connect方法中直接返回一个NettyClient(url, listener);,下面看下具体的NettyClient初始化细节,会先初始化AbstractPeer这里只是吧url和handler赋值;然后是AbstractEndpoint初始化:

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public AbstractEndpoint(URL url, ChannelHandler handler) {
super(url, handler);
//获取编解码器,这里是DubboCountCodec
this.codec = getChannelCodec(url);
this.timeout = url.getPositiveParameter(Constants.TIMEOUT_KEY, Constants.DEFAULT_TIMEOUT);
this.connectTimeout = url.getPositiveParameter(Constants.CONNECT_TIMEOUT_KEY, Constants.DEFAULT_CONNECT_TIMEOUT);
}

接着是AbstractClient的初始化:

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public AbstractClient(URL url, ChannelHandler handler) throws RemotingException {
super(url, handler);
send_reconnect = url.getParameter(Constants.SEND_RECONNECT_KEY, false);
shutdown_timeout = url.getParameter(Constants.SHUTDOWN_TIMEOUT_KEY, Constants.DEFAULT_SHUTDOWN_TIMEOUT);
//默认重连间隔2s,1800表示1小时warning一次.
reconnect_warning_period = url.getParameter("reconnect.waring.period", 1800);

try {
//具体实现在子类中
doOpen();
} catch (Throwable t) {。。。 }
try {
// 连接
connect();
} catch (RemotingException t) {。。。}
// TODO暂没理解
executor = (ExecutorService) ExtensionLoader.getExtensionLoader(DataStore.class)
.getDefaultExtension().get(Constants.CONSUMER_SIDE, Integer.toString(url.getPort()));
ExtensionLoader.getExtensionLoader(DataStore.class)
.getDefaultExtension().remove(Constants.CONSUMER_SIDE, Integer.toString(url.getPort()));
}

看下在NettyClient中doOpen()的实现:

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protected void doOpen() throws Throwable {
NettyHelper.setNettyLoggerFactory();
bootstrap = new ClientBootstrap(channelFactory);
// config
// @see org.jboss.netty.channel.socket.SocketChannelConfig
bootstrap.setOption("keepAlive", true);
bootstrap.setOption("tcpNoDelay", true);
bootstrap.setOption("connectTimeoutMillis", getTimeout());
final NettyHandler nettyHandler = new NettyHandler(getUrl(), this);
bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
public ChannelPipeline getPipeline() {
NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec(), getUrl(), NettyClient.this);
ChannelPipeline pipeline = Channels.pipeline();
pipeline.addLast("decoder", adapter.getDecoder());
pipeline.addLast("encoder", adapter.getEncoder());
pipeline.addLast("handler", nettyHandler);
return pipeline;
}
});
}

这里是Netty3中的客户端连接的一些常规步骤,暂不做具体解析。open之后,就是真正连接服务端的操作了,connect():

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protected void connect() throws RemotingException {
connectLock.lock();
try {
if (isConnected()) {
return;
}
//初始化重连的线程
initConnectStatusCheckCommand();
//连接,在子类中实现
doConnect();
reconnect_count.set(0);
reconnect_error_log_flag.set(false);
} catch (RemotingException e) {。。。} finally {
connectLock.unlock();
}
}

NettyClient中的doConnect方法:

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protected void doConnect() throws Throwable {
long start = System.currentTimeMillis();
//消费者端开始连接,这一步的时候,服务提供者端就接到了连接请求,开始处理了
ChannelFuture future = bootstrap.connect(getConnectAddress());
try{
boolean ret = future.awaitUninterruptibly(getConnectTimeout(), TimeUnit.MILLISECONDS);
if (ret && future.isSuccess()) {
Channel newChannel = future.getChannel();
newChannel.setInterestOps(Channel.OP_READ_WRITE);
try {
// 关闭旧的连接
Channel oldChannel = NettyClient.this.channel; // copy reference
if (oldChannel != null) {
try {
oldChannel.close();
} finally {
NettyChannel.removeChannelIfDisconnected(oldChannel);
}
}
} finally {
if (NettyClient.this.isClosed()) {
try {
newChannel.close();
} finally {
NettyClient.this.channel = null;
NettyChannel.removeChannelIfDisconnected(newChannel);
}
} else {
NettyClient.this.channel = newChannel;
}
}
} else if (future.getCause() != null) { throw。。。 } else {throw 。。。 }
}finally{
if (! isConnected()) {
future.cancel();
}
}
}

这里连接的细节都交给了netty。

NettyClient初始化完成之后,返回给Transporters,再返回给HeaderExchanger,HeaderExchanger中将NettyClient包装成HeaderExchangeClient返回给DubboProtocol的initClient方法中,到此在getSharedClient中就获取到了一个ExchangeClient,然后包装一下返回client = new ReferenceCountExchangeClient(exchagneclient, ghostClientMap);

到这里在DubboProtocol的refer方法中这句DubboInvoker<T> invoker = new DubboInvoker<T>(serviceType, url, getClients(url), invokers);创建DubboInvoker就已经解析完成,创建过程中连接了服务端,包含一个ExchangeClient等:

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public <T> Invoker<T> refer(Class<T> serviceType, URL url) throws RpcException {
// create rpc invoker.
DubboInvoker<T> invoker = new DubboInvoker<T>(serviceType, url, getClients(url), invokers);
//将invoker缓存
invokers.add(invoker);
//返回invoker
return invoker;
}

接着返回ProtocolFilterWrapper的refer方法,在这里会构建invoker链:

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public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
return protocol.refer(type, url);
}
return buildInvokerChain(protocol.refer(type, url), Constants.REFERENCE_FILTER_KEY, Constants.CONSUMER);
}

接着再返回到ProtocolListenerWrapper的refer方法,这里会初始化监听器,包装:

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public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
return protocol.refer(type, url);
}
return new ListenerInvokerWrapper<T>(protocol.refer(type, url),
Collections.unmodifiableList(
ExtensionLoader.getExtensionLoader(InvokerListener.class)
.getActivateExtension(url, Constants.INVOKER_LISTENER_KEY)));
}

接着在返回到toInvokers方法,然后返回refreshInvoker方法的Map<String, Invoker<T>> newUrlInvokerMap = toInvokers(invokerUrls) ;这就获得了Invoker,接着就是方法名映射Invoker列表:Map<String, List<Invoker<T>>> newMethodInvokerMap = toMethodInvokers(newUrlInvokerMap);这里将invokers列表转成与方法的映射关系。到这里refreshInvoker方法就完成了,在往上就返回到AbstractRegistry的notify方法,到这里也完成了。

创建服务代理

到这里有关消费者端注册到注册中心和订阅注册中心就完事儿了,这部分是在RegistryProtocol.doRefer方法中,这个方法最后一句是return cluster.join(directory);,这里由Cluster组件创建一个Invoker并返回,这里的cluster默认是用FailoverCluster,最后返回的是经过MockClusterInvoker包装过的FailoverCluster。继续返回到ReferenceConfig中createProxy方法,这时候我们已经完成了消费者端引用服务的Invoker。然后最后返回的是根据我们得到的invoker创建的服务代理return (T) proxyFactory.getProxy(invoker);。这里proxyFactory是我们在最上面列出的动态生成的代码。

首先经过AbstractProxyFactory的处理:

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public <T> T getProxy(Invoker<T> invoker) throws RpcException {
Class<?>[] interfaces = null;
String config = invoker.getUrl().getParameter("interfaces");
if (config != null && config.length() > 0) {
String[] types = Constants.COMMA_SPLIT_PATTERN.split(config);
if (types != null && types.length > 0) {
interfaces = new Class<?>[types.length + 2];
interfaces[0] = invoker.getInterface();
interfaces[1] = EchoService.class;
for (int i = 0; i < types.length; i ++) {
interfaces[i + 1] = ReflectUtils.forName(types[i]);
}
}
}
if (interfaces == null) {
interfaces = new Class<?>[] {invoker.getInterface(), EchoService.class};
}
//这里默认使用的是JavassistProxyFactory的实现
return getProxy(invoker, interfaces);
}

然后经过StubProxyFactoryWrapper的处理:

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public <T> T getProxy(Invoker<T> invoker) throws RpcException {
T proxy = proxyFactory.getProxy(invoker);
if (GenericService.class != invoker.getInterface()) {
String stub = invoker.getUrl().getParameter(Constants.STUB_KEY, invoker.getUrl().getParameter(Constants.LOCAL_KEY));
if (ConfigUtils.isNotEmpty(stub)) {
Class<?> serviceType = invoker.getInterface();
if (ConfigUtils.isDefault(stub)) {
if (invoker.getUrl().hasParameter(Constants.STUB_KEY)) {
stub = serviceType.getName() + "Stub";
} else {
stub = serviceType.getName() + "Local";
}
}
try {
Class<?> stubClass = ReflectUtils.forName(stub);
if (! serviceType.isAssignableFrom(stubClass)) {
throw new IllegalStateException("The stub implemention class " + stubClass.getName() + " not implement interface " + serviceType.getName());
}
try {
Constructor<?> constructor = ReflectUtils.findConstructor(stubClass, serviceType);
proxy = (T) constructor.newInstance(new Object[] {proxy});
//export stub service
URL url = invoker.getUrl();
if (url.getParameter(Constants.STUB_EVENT_KEY, Constants.DEFAULT_STUB_EVENT)){
url = url.addParameter(Constants.STUB_EVENT_METHODS_KEY, StringUtils.join(Wrapper.getWrapper(proxy.getClass()).getDeclaredMethodNames(), ","));
url = url.addParameter(Constants.IS_SERVER_KEY, Boolean.FALSE.toString());
try{
export(proxy, (Class)invoker.getInterface(), url);
}catch (Exception e) {
LOGGER.error("export a stub service error.", e);
}
}
} catch (NoSuchMethodException e) {
throw new IllegalStateException("No such constructor \"public " + stubClass.getSimpleName() + "(" + serviceType.getName() + ")\" in stub implemention class " + stubClass.getName(), e);
}
} catch (Throwable t) {
LOGGER.error("Failed to create stub implemention class " + stub + " in consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() + ", cause: " + t.getMessage(), t);
// ignore
}
}
}
return proxy;
}

返回代理。到此HelloService helloService = (HelloService) applicationContext.getBean("helloService");就解析完成了,得到了服务的代理,代理会被注册到Spring容器中,可以调用服务方法了。接下来的方法调用过程,是消费者发送请求,提供者处理,然后消费者接受处理结果的请求。

初始化的过程:主要做了注册到注册中心,监听注册中心,连接到服务提供者端,创建代理。这些都是为了下面消费者和提供者之间的通信做准备。

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