Dubbo服务发布

dubbo服务发布影响流程的主要包括三个部分，依次是：

1. 服务暴露
2. 心跳
3. 服务注册

服务暴露是对外提供服务及暴露端口，以便消费端可以正常调通服务。心跳机制保证服务器端及客户端正常长连接的保持，服务注册是向注册中心注册服务暴露服务的过程。

Dubbo服务暴露

此处只记录主要代码部分以便能快速定位到主要的核心代码：

ServiceConfig.java中代码

if (registryURLs != null && registryURLs.size() > 0
&& url.getParameter(“register”, true)) {
// 循环祖册中心 URL 数组 registryURLs
for (URL registryURL : registryURLs) {
// “dynamic” ：服务是否动态注册，如果设为false，注册后将显示后disable状态，需人工启用，并且服务提供者停止时，也不会自动取消册，需人工禁用。
url = url.addParameterIfAbsent(“dynamic”, registryURL.getParameter(“dynamic”));
// 获得监控中心 URL
URL monitorUrl = loadMonitor(registryURL);
if (monitorUrl != null) {
// 将监控中心的 URL 作为 “monitor” 参数添加到服务提供者的 URL 中，并且需要编码。通过这样的方式，服务提供者的 URL 中，包含了监控中心的配置。
url = url.addParameterAndEncoded(Constants.MONITOR_KEY, monitorUrl.toFullString());
}
if (logger.isInfoEnabled()) {
logger.info(“Register dubbo service ” interfaceClass.getName() ” url ” url ” to registry ” registryURL);
}
// 使用 ProxyFactory 创建 Invoker 对象
// 调用 URL#addParameterAndEncoded(key, value) 方法，将服务体用这的 URL 作为 “export” 参数添加到注册中心的 URL 中。通过这样的方式，注册中心的 URL 中，包含了服务提供者的配置。
// 创建 Invoker 对象。该 Invoker 对象，执行 #invoke(invocation) 方法时，内部会调用 Service 对象( ref )对应的调用方法。
Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString()));
// 使用 Protocol 暴露 Invoker 对象
/**
* Protocol$Adaptive => ProtocolFilterWrapper => ProtocolListenerWrapper => RegistryProtocol
* =>
* Protocol$Adaptive => ProtocolFilterWrapper => ProtocolListenerWrapper => DubboProtocol
*/
Exporter<?> exporter = protocol.export(invoker);
// 添加到 `exporters`
exporters.add(exporter);
}
}

循环注册中心，对每个注册中心都执行代码块中的执行过程

1.如果url中没有dynamic 参数，则从registerUrl中取值，并赋予url

dynamic是服务动态注册的标识，默认为true，如果设置为false,则服务注册后显示disable状态，需人工启动

2.加载注册中心对应的监控中心配置

3.如果注册中心不为空则设置url的 monitor参数

4.Invoker proxyFactory.getInvoker proxyFactory 默认为JavassistProxyFactory对象，这段代码为创建 ref 服务对象的代理对象。

proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString())); 获取ref的代理对象并在registryURL 中添加export属性，代理对象中属性参数如下

5.protocol.export(invoker) 为暴露服务的核心实现部分,协议的调用链如下：

/**

* Protocol$Adaptive => ProtocolFilterWrapper => ProtocolListenerWrapper => RegistryProtocol

* =>

* Protocol$Adaptive => ProtocolFilterWrapper => ProtocolListenerWrapper => DubboProtocol

*/

其中DubboProtocol 实现了服务暴露及心跳检测功能

RegistryProtocol 调用了DubboProtocol及注册服务

接下来经过两个扩展类(包装器) ProtocolFilterWrapper和ProtocolListenerWrapper 进入RegistryProtocol 核心代码如下：

public <T> Exporter<T> export(final Invoker<T> originInvoker) throws rpcException {
// 暴露服务
//export invoker
final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker);
//registry provider
final Registry registry = getRegistry(originInvoker);
// 获得服务提供者 URL
final URL registedProviderUrl = getRegistedProviderUrl(originInvoker);
registry.register(registedProviderUrl);
// 订阅override数据
// FIXME 提供者订阅时，会影响同一JVM即暴露服务，又引用同一服务的的场景，因为subscribed以服务名为缓存的key，导致订阅信息覆盖。
final URL overrideSubscribeUrl = getSubscribedOverrideUrl(registedProviderUrl);
final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
//保证每次export都返回一个新的exporter实例
return new Exporter<T>() {
public Invoker<T> getInvoker() {
return exporter.getInvoker();
}
public void unexport() {
try {
exporter.unexport();
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
try {
registry.unregister(registedProviderUrl);
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
try {
overrideListeners.remove(overrideSubscribeUrl);
registry.unsubscribe(overrideSubscribeUrl, overrideSubscribeListener);
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
}
};
}

/**
* 暴露服务。
*
* 此处的 Local 指的是，本地启动服务，但是不包括向注册中心注册服务的意思。
* @param originInvoker
* @param <T>
* @return
*/
@SuppressWarnings(“unchecked”)
private <T> ExporterChangeableWrapper<T> doLocalExport(final Invoker<T> originInvoker) {
// 获得在 `bounds` 中的缓存 Key
//dubbo://192.168.20.218:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&default.accepts=1000&default.threadpool=fixed&default.threads=100&default.timeout=5000&dubbo=2.0.0&generic=false&
// interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&owner=uce&pid=1760&side=provider&timestamp=1530150456618
String key = getCacheKey(originInvoker);
ExporterChangeableWrapper<T> exporter = (ExporterChangeableWrapper<T>) bounds.get(key);
if (exporter == null) {
synchronized (bounds) {
exporter = (ExporterChangeableWrapper<T>) bounds.get(key);
// 未暴露过，进行暴露服务
if (exporter == null) {
// InvokerDelegete 实现 com.alibaba.dubbo.rpc.protocol.InvokerWrapper 类，主要增加了 #getInvoker() 方法，获得真实的，非 InvokerDelegete 的 Invoker 对象。
// 因为，可能会存在 InvokerDelegete.invoker 也是 InvokerDelegete 类型的情况。 getProviderUrl 同上 key = getCacheKey
final Invoker<?> invokerDelegete = new InvokerDelegete<T>(originInvoker, getProviderUrl(originInvoker));
// 暴露服务，创建 Exporter 对象
Exporter<T> export = (Exporter<T>) protocol.export(invokerDelegete);
// 使用 创建的Exporter对象 originInvoker ，创建 ExporterChangeableWrapper 对象
exporter = new ExporterChangeableWrapper<T>(export, originInvoker);
bounds.put(key, exporter);
}
}
}
return exporter;
}

1.代用同步锁 double-check的方式来保证同样的服务不重复暴露。

2.new InvokerDelegete<T>(originInvoker, getProviderUrl(originInvoker));

InvokerDelegete 实现 com.alibaba.dubbo.rpc.protocol.InvokerWrapper（invoke） 类，主要增加了 #getInvoker() 方法，获得真实的，非 InvokerDelegete 的 Invoker 对象。

3.调用protocol.export接口 经过ProtocolFilterWrapper.invoker方法 创过滤器链再暴露服务：

protocol.export(buildInvokerChain(invoker, Constants.SERVICE_FILTER_KEY, Constants.PROVIDER));

/**
* 构建过滤器链
* @param invoker injvm://127.0.0.1/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&default.accepts=1000&default.threadpool=fixed&default.threads=100&default.timeout=5000&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&owner=uce&pid=9932&side=provider&timestamp=1527930395583
* @param key service.filter 该参数用于获得 ServiceConfig 或 ReferenceConfig 配置的自定义过滤器
* 以 ServiceConfig 举例子，例如 url = injvm://127.0.0.1/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&bind.ip=192.168.3.17&bind.port=20880&default.delay=-1&default.retries=0&default.service.filter=demo&delay=-1&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=81844&qos.port=22222&service.filter=demo&side=provider&timestamp=1520682156043 中，
* service.filter=demo，这是笔者配置自定义的 DemoFilter 过滤器。
* <dubbo:service interface=”com.alibaba.dubbo.demo.DemoService” ref=”demoService” filter=”demo” />
* @param group provider 属性，分组
* 在暴露服务时，group = provider 。
* 在引用服务时，group = consumer 。
* @param <T>
* @return
*/
private static <T> Invoker<T> buildInvokerChain(final Invoker<T> invoker, String key, String group) {
Invoker<T> last = invoker;
List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group);
/* EchoFilter
ClassLoaderFilter
GenericFilter
ContextFilter
TraceFilter
TimeoutFilter
MonitorFilter
ExceptionFilter
DemoFilter 【自定义】*/
//倒序循环 Filter ，创建带 Filter 链的 Invoker 对象。因为是通过嵌套声明匿名类循环调用的方式，所以要倒序。可以手工模拟下这个过程。通过这样的方式，实际过滤的顺序，还是我们上面看到的正序
if (filters.size() > 0) {
for (int i = filters.size() – 1; i >= 0; i–) {
final Filter filter = filters.get(i);
final Invoker<T> next = last;
last = new Invoker<T>() {
@Override
public Class<T> getInterface() {
return invoker.getInterface();
}
@Override
public URL getUrl() {
return invoker.getUrl();
}
@Override
public boolean isAvailable() {
return invoker.isAvailable();
}
@Override
public Result invoke(Invocation invocation) throws RpcException {
return filter.invoke(next, invocation);
}
@Override
public void destroy() {
invoker.destroy();
}
@Override
public String toString() {
return invoker.toString();
}
};
}
}
return last;
}

List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group);

获取Active的属于指定组的过过滤器列表

参考文章：https://my.oschina.net/LucasZhu/blog/1835048

接下来执行DubboProrocol进行服务暴露的过程。

public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
URL url = invoker.getUrl();
// export service.
String key = serviceKey(url);
// 创建 DubboExporter 对象，并添加到 `exporterMap` 。
DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap);
exporterMap.put(key, exporter);
//export an stub service for dispaching event
Boolean isStubSupportEvent = url.getParameter(Constants.STUB_EVENT_KEY, Constants.DEFAULT_STUB_EVENT);
Boolean isCallbackservice = url.getParameter(Constants.IS_CALLBACK_SERVICE, false);
if (isStubSupportEvent && !isCallbackservice) {
String stubServiceMethods = url.getParameter(Constants.STUB_EVENT_METHODS_KEY);
if (stubServiceMethods == null || stubServiceMethods.length() == 0) {
if (logger.isWarnEnabled()) {
logger.warn(new IllegalStateException(“consumer [” url.getParameter(Constants.INTERFACE_KEY)
“], has set stubproxy support event ,but no stub methods founded.”));
}
} else {
stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods);
}
}
// 启动服务器
openServer(url);
return exporter;
}

1.获取invoker的 URL信息

2.获取key信息 为URL中interface与暴露端口的拼装字符串：com.alibaba.dubbo.demo.DemoService:20880

3.创建DubboExporter对象 并且入参为exporterMap

4.将exporter对象添加到exporterMap中

/**
* 启动服务器
*
* @param url URL
*/
private void openServer(URL url) {
// find server.
String key = url.getAddress();
//client 也可以暴露一个只有server可以调用的服务。
boolean isServer = url.getParameter(Constants.IS_SERVER_KEY, true);
if (isServer) {
ExchangeServer server = serverMap.get(key);
if (server == null) {
serverMap.put(key, createServer(url));
} else {
//server支持reset,配合override功能使用
server.reset(url);
}
}
}

调用createServer()方法 并存入DubboProtocol的serverMap中

private ExchangeServer createServer(URL url) {
//默认开启server关闭时发送readonly事件
url = url.addParameterIfAbsent(Constants.channel_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString());
//默认开启heartbeat
url = url.addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT));
String str = url.getParameter(Constants.SERVER_KEY, Constants.DEFAULT_REMOTING_SERVER);
// 校验 Server 的 Dubbo SPI 拓展是否存在
if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str))
throw new RpcException(“Unsupported server type: ” str “, url: ” url);
// 设置codec为 `”Dubbo”`
url = url.addParameter(Constants.CODEC_KEY, Version.isCompatibleVersion() ? COMPATIBLE_CODEC_NAME : DubboCodec.NAME);
ExchangeServer server;
try {
server = Exchangers.bind(url, requestHandler);
} catch (RemotingException e) {
throw new RpcException(“Fail to start server(url: ” url “) ” e.getMessage(), e);
}
str = url.getParameter(Constants.CLIENT_KEY);
if (str != null && str.length() > 0) {
Set<String> supportedTypes = ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions();
if (!supportedTypes.contains(str)) {
throw new RpcException(“Unsupported client type: ” str);
}
}
return server;
}

1.默认开启server 关闭时发送readonly事件：channel.readonly.sent : true

2.默认开启 heartbeat

3.获取服务暴露的 server 传输 ， 默认为netty

4.设置编码器为Dubbo也就是 DubboCountCodec

5.Exchangers#bind(url, requestHandler) 启动服务器，requestHandler结构如下

具体实现代码如下：

private ExchangeHandler requestHandler = new ExchangeHandlerAdapter() {
public Object reply(ExchangeChannel channel, Object message) throws RemotingException {
if (message instanceof Invocation) {
Invocation inv = (Invocation) message;
Invoker<?> invoker = getInvoker(channel, inv);
//如果是callback 需要处理高版本调用低版本的问题
if (Boolean.TRUE.toString().equals(inv.getAttachments().get(IS_CALLBACK_SERVICE_INVOKE))) {
String methodsStr = invoker.getUrl().getParameters().get(“methods”);
boolean hasMethod = false;
if (methodsStr == null || methodsStr.indexOf(“,”) == -1) {
hasMethod = inv.getMethodName().equals(methodsStr);
} else {
String[] methods = methodsStr.split(“,”);
for (String method : methods) {
if (inv.getMethodName().equals(method)) {
hasMethod = true;
break;
}
}
}
if (!hasMethod) {
logger.warn(new IllegalStateException(“The methodName ” inv.getMethodName() ” not found in callback service interface ,invoke will be ignored. please update the api interface. url is:” invoker.getUrl()) ” ,invocation is :” inv);
return null;
}
}
RpcContext.getContext().setRemoteAddress(channel.getRemoteAddress());
return invoker.invoke(inv);
}
throw new RemotingException(channel, “Unsupported request: ” message == null ? null : (message.getClass().getName() “: ” message) “, channel: consumer: ” channel.getRemoteAddress() ” –> provider: ” channel.getLocalAddress());
}
@Override
public void received(Channel channel, Object message) throws RemotingException {
if (message instanceof Invocation) {
reply((ExchangeChannel) channel, message);
} else {
super.received(channel, message);
}
}
@Override
public void connected(Channel channel) throws RemotingException {
invoke(channel, Constants.ON_CONNECT_KEY);
}
@Override
public void disconnected(Channel channel) throws RemotingException {
if (logger.isInfoEnabled()) {
logger.info(“disconected from ” channel.getRemoteAddress() “,url:” channel.getUrl());
}
invoke(channel, Constants.ON_DISCONNECT_KEY);
}
private void invoke(Channel channel, String methodKey) {
Invocation invocation = createInvocation(channel, channel.getUrl(), methodKey);
if (invocation != null) {
try {
received(channel, invocation);
} catch (Throwable t) {
logger.warn(“Failed to invoke event method ” invocation.getMethodName() “(), cause: ” t.getMessage(), t);
}
}
}
private Invocation createInvocation(Channel channel, URL url, String methodKey) {
String method = url.getParameter(methodKey);
if (method == null || method.length() == 0) {
return null;
}
RpcInvocation invocation = new RpcInvocation(method, new Class<?>[0], new Object[0]);
invocation.setAttachment(Constants.PATH_KEY, url.getPath());
invocation.setAttachment(Constants.GROUP_KEY, url.getParameter(Constants.GROUP_KEY));
invocation.setAttachment(Constants.INTERFACE_KEY, url.getParameter(Constants.INTERFACE_KEY));
invocation.setAttachment(Constants.VERSION_KEY, url.getParameter(Constants.VERSION_KEY));
if (url.getParameter(Constants.STUB_EVENT_KEY, false)) {
invocation.setAttachment(Constants.STUB_EVENT_KEY, Boolean.TRUE.toString());
}
return invocation;
}
};

Exchangeers.bind(URL url, ExchangeHandler handler)

public static ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {
if (url == null) {
throw new IllegalArgumentException(“url == null”);
}
if (handler == null) {
throw new IllegalArgumentException(“handler == null”);
}
url = url.addParameterIfAbsent(Constants.CODEC_KEY, “exchange”);
return getExchanger(url).bind(url, handler);
}
public static Exchanger getExchanger(URL url) {
String type = url.getParameter(Constants.EXCHANGER_KEY, Constants.DEFAULT_EXCHANGER);
return getExchanger(type);
}
public static Exchanger getExchanger(String type) {
return ExtensionLoader.getExtensionLoader(Exchanger.class).getExtension(type);
}

接口作用是设置exchanger params为header 并且获取Exchanger.class的header扩展接口HeaderExchanger， 并调用bind方法：

public class HeaderExchanger implements Exchanger {
public static final String NAME = “header”;
public ExchangeClient connect(URL url, ExchangeHandler handler) throws RemotingException {
return new HeaderExchangeClient(Transporters.connect(url, new DecodeHandler(new HeaderExchangeHandler(handler))), true);
}
public ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {
return new HeaderExchangeServer(Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler))));
}
}

先将 DubboProtocol入参 传过来的ExchangeHandler对象ExchangeHandlerAdapter() 进行包装组成handler链：最后返回ChannelHandler对象，接下来调用：Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler)))

Server Transporters.bind(URL url, ChannelHandler… handlers)

Transpoter$Adaptive.bind()

数据透传 NettyTransporter.java

Server NettyTransporter.bind(URL url, ChannelHandler listener)

public Server bind(URL url, ChannelHandler listener) throws RemotingException {
return new NettyServer(url, listener);
}

作用是：

返回一个NettyServer实例：

public NettyServer(URL url, ChannelHandler handler) throws RemotingException {
super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));
}

ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)) 只用是生成获取ThreadName的名称 为URL添加threadname的param

ChannelHandlers.wrap(ChannelHandler handler, URL url) 代码如下：

public class ChannelHandlers {
private static ChannelHandlers INSTANCE = new ChannelHandlers();
protected ChannelHandlers() {
}
public static ChannelHandler wrap(ChannelHandler handler, URL url) {
return ChannelHandlers.getInstance().wrapInternal(handler, url);
}
protected static ChannelHandlers getInstance() {
return INSTANCE;
}
static void setTestingChannelHandlers(ChannelHandlers instance) {
INSTANCE = instance;
}
protected ChannelHandler wrapInternal(ChannelHandler handler, URL url) {
return new MultiMessageHandler(new HeartbeatHandler(ExtensionLoader.getExtensionLoader(Dispatcher.class)
.getAdaptiveExtension().dispatch(handler, url)));
}
}

ExtensionLoader.getExtensionLoader(Dispatcher.class).getAdaptiveExtension().dispatch(handler, url)：

获取到AllDispatcher分发器进行透传：

public class AllDispatcher implements Dispatcher {
public static final String NAME = “all”;
public ChannelHandler dispatch(ChannelHandler handler, URL url) {
return new AllChannelHandler(handler, url);
}
}

结构如图所示：

调用WrappedChannelHandler的构造方法：

public WrappedChannelHandler(ChannelHandler handler, URL url) {
this.handler = handler;
this.url = url;
executor = (ExecutorService) ExtensionLoader.getExtensionLoader(ThreadPool.class).getAdaptiveExtension().getExecutor(url);
String componentKey = Constants.EXECUTOR_SERVICE_COMPONENT_KEY;
if (Constants.CONSUMER_SIDE.equalsIgnoreCase(url.getParameter(Constants.SIDE_KEY))) {
componentKey = Constants.CONSUMER_SIDE;
}
DataStore dataStore = ExtensionLoader.getExtensionLoader(DataStore.class).getDefaultExtension();
dataStore.put(componentKey, Integer.toString(url.getPort()), executor);
}

这段代码的功能为：

1.将 之前头创的DecoderHandler对象再进包装 包装为AllChannelHandler

2.生成线程池对象Executor对象

3.获取默认的DataStore对象，并将线程池对象放入DataStore 中 key为 : java.util.concurrent.ExecutorService 字符串和服务暴露的端口 值为线程池对象

return new MultiMessageHandler(new HeartbeatHandler(ExtensionLoader.getExtensionLoader(Dispatcher.class)

.getAdaptiveExtension().dispatch(handler, url)));

接下来将返回的AllChannelHandler对象用HeartbeatHandler 和 MultiMessageHandler 进行包装处理并返回ChannelHandler.wrap() 的上一端。

NettyTransporter.bind(URL url, ChannelHandler listener) -> new NettyServer(URL url, ChannelHandler handler)

-> super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));

接下来是创建NettyServer对象的最后一步：

NettyServer ==>
public NettyServer(URL url, ChannelHandler handler) throws RemotingException {
super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));
}
AbstractServer==>
public AbstractServer(URL url, ChannelHandler handler) throws RemotingException {
super(url, handler);
localAddress = getUrl().toInetSocketAddress();
String host = url.getParameter(Constants.ANYHOST_KEY, false)
|| NetUtils.isInvalidLocalHost(getUrl().getHost())
? NetUtils.ANYHOST : getUrl().getHost();
bindAddress = new InetSocketAddress(host, getUrl().getPort());
this.accepts = url.getParameter(Constants.ACCEPTS_KEY, Constants.DEFAULT_ACCEPTS);
this.idleTimeout = url.getParameter(Constants.IDLE_TIMEOUT_KEY, Constants.DEFAULT_IDLE_TIMEOUT);
try {
doOpen();
if (logger.isInfoEnabled()) {
logger.info(“Start ” getClass().getSimpleName() ” bind ” getBindAddress() “, export ” getLocalAddress());
}
} catch (Throwable t) {
throw new RemotingException(url.toInetSocketAddress(), null, “Failed to bind ” getClass().getSimpleName()
” on ” getLocalAddress() “, cause: ” t.getMessage(), t);
}
//fixme replace this with better method
DataStore dataStore = ExtensionLoader.getExtensionLoader(DataStore.class).getDefaultExtension();
executor = (ExecutorService) dataStore.get(Constants.EXECUTOR_SERVICE_COMPONENT_KEY, Integer.toString(url.getPort()));
}
AbstractEndpoint ==>
public AbstractEndpoint(URL url, ChannelHandler handler) {
super(url, handler);
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);
}
AbstractPeer==>
public AbstractPeer(URL url, ChannelHandler handler) {
if (url == null) {
throw new IllegalArgumentException(“url == null”);
}
if (handler == null) {
throw new IllegalArgumentException(“handler == null”);
}
this.url = url;
this.handler = handler;
}

调用栈如上所示：

因为之前设置了codec为dubbo 所以返回DubboCountCodec实例

获取超时时间timeout ,和链接的超时时间connectTimeout

localAddress为本地IP:PORT port为服务暴露的端口

host 为0.0.0.0

bindAddress为 host:port port为服务暴露的端口

this.accept 为默认获取最大连接数

idleTimeout为 url中 idle.timeout

核心代码：doOpen()

@Override
protected void doOpen() throws Throwable {
NettyHelper.setNettyLoggerFactory();
ExecutorService boss = Executors.newCachedThreadPool(new NamedThreadFactory(“NettyServerBoss”, true));
ExecutorService worker = Executors.newCachedThreadPool(new NamedThreadFactory(“NettyServerWorker”, true));
ChannelFactory channelFactory = new NioServerSocketChannelFactory(boss, worker, getUrl().getPositiveParameter(Constants.IO_THREADS_KEY, Constants.DEFAULT_IO_THREADS));
bootstrap = new ServerBootstrap(channelFactory);
final NettyHandler nettyHandler = new NettyHandler(getUrl(), this);
channels = nettyHandler.getChannels();
// https://issues.jboss.org/browse/NETTY-365
// https://issues.jboss.org/browse/NETTY-379
// final Timer timer = new HashedWheelTimer(new NamedThreadFactory(“NettyIdleTimer”, true));
bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
public ChannelPipeline getPipeline() {
NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec(), getUrl(), NettyServer.this);
ChannelPipeline pipeline = Channels.pipeline();
/*int idleTimeout = getIdleTimeout();
if (idleTimeout > 10000) {
pipeline.addLast(“timer”, new IdleStateHandler(timer, idleTimeout / 1000, 0, 0));
}*/
pipeline.addLast(“decoder”, adapter.getDecoder());
pipeline.addLast(“encoder”, adapter.getEncoder());
pipeline.addLast(“handler”, nettyHandler);
return pipeline;
}
});
// bind
channel = bootstrap.bind(getBindAddress());
}

1.首先进行Netty的日志配置

接下来先生成 NettyCodecAdapter 入参为之前生成的codec , URL信息(主要用到buffer属性配置Netty缓冲区)及 this (Handler) 对象

接下来就是设置Netty的Encoder Decoder 来进行数据的编码与解码 其会调用 this的handler链来进行数据处理。Dubbo2.5.6采用的是Netty3来进行通讯的，此处就不进行赘述。

AbstractServer 接下来获取到从DataStore对象中获取之前缓存的线程池 ，设置 NettyServer的 executor属性。

自此，Dubbo服务暴露的代码解析完毕，NettyServer的类结构图如下：

心跳服务

Dubbo provider的心跳服务是 HeaderExchanger bind代码执行的最后一步：参数是上面生成的Server对象 (NettyServer)。

public HeaderExchangeServer(Server server) {
if (server == null) {
throw new IllegalArgumentException(“server == null”);
}
this.server = server;
this.heartbeat = server.getUrl().getParameter(Constants.HEARTBEAT_KEY, 0);
this.heartbeatTimeout = server.getUrl().getParameter(Constants.HEARTBEAT_TIMEOUT_KEY, heartbeat * 3);
if (heartbeatTimeout < heartbeat * 2) {
throw new IllegalStateException(“heartbeatTimeout < heartbeatInterval * 2”);
}
startHeatbeatTimer();
}

1.初始化 server信息

2.获取server URL中heartbeat信息 及心跳超时信息，默认为heartbeat的三倍

3.执行心跳代码 startHeatbeatTimer()

private void startHeatbeatTimer() {
stopHeartbeatTimer();
if (heartbeat > 0) {
heatbeatTimer = scheduled.scheduleWithFixedDelay(
new HeartBeatTask(new HeartBeatTask.ChannelProvider() {
public Collection<Channel> getChannels() {
return Collections.unmodifiableCollection(
HeaderExchangeServer.this.getChannels());
}
}, heartbeat, heartbeatTimeout),
heartbeat, heartbeat, TimeUnit.MILLISECONDS);
}
}

1.停止定时任务——首先停止定时器中所有任务，置空 beatbeatTimer；

2.重新设置定时器 ， 循环检测

接下来在DubboProtocol的openServer(URL) 方法中将创建的ExchangeServer对象放入 DubboProtocol的 serverMap 集合对象中

key为服务的ip:port 如 192.168.20.218:20880

value为之前创建的ExchangeServer对象

DubboProtocol export方法到此执行完毕，最终返回的是 DubboExporter对象包装了入参的invoker对象，serviceKey信息，及服务暴露的 exporterMap对象。

服务注册

我们接着来看RegistryProtocol 接下来的执行代码：

public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
// 暴露服务
//export invoker
final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker);
//registry provider 添加定时任务 ping request response
final Registry registry = getRegistry(originInvoker);
// 获得服务提供者 URL
final URL registedProviderUrl = getRegistedProviderUrl(originInvoker);
registry.register(registedProviderUrl);
// 订阅override数据
// FIXME 提供者订阅时，会影响同一JVM即暴露服务，又引用同一服务的的场景，因为subscribed以服务名为缓存的key，导致订阅信息覆盖。
final URL overrideSubscribeUrl = getSubscribedOverrideUrl(registedProviderUrl);
final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
//保证每次export都返回一个新的exporter实例
return new Exporter<T>() {
public Invoker<T> getInvoker() {
return exporter.getInvoker();
}
public void unexport() {
try {
exporter.unexport();
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
try {
registry.unregister(registedProviderUrl);
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
try {
overrideListeners.remove(overrideSubscribeUrl);
registry.unsubscribe(overrideSubscribeUrl, overrideSubscribeListener);
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
}
};
}

1.ExporterChangeableWrapper<T> doLocalExport(final Invoker<T> originInvoker) 为暴露服务的执行过程，上面流程已经走过。

返回的数据格式如下：

2.根据originInvoker中注册中心信息获取对应的Registry对象,因为这里是zookeeper协议，所以为ZookeeperRegistry对象

3.从注册中心的URL中获得 export 参数对应的值，即服务提供者的URL.

4.registry.register(registedProviderUrl); 用之前创建的注册中心对象注册服务

5.

// TODO

上面提到 Registry getRegistry(final Invoker<?> originInvoker) 是根据invoker的地址获取registry实例代码如下：

private Registry getRegistry(final Invoker<?> originInvoker) {
// registry://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&export=dubbo://192.168.20.218:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&default.accepts=1000&default.threadpool=fixed&default.threads=100&default.timeout=5000&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&owner=uce&pid=12028&side=provider&timestamp=1531912729429&owner=uce&pid=12028&registry=zookeeper&timestamp=1531912729343
URL registryUrl = originInvoker.getUrl();
if (Constants.REGISTRY_PROTOCOL.equals(registryUrl.getProtocol())) {
String protocol = registryUrl.getParameter(Constants.REGISTRY_KEY, Constants.DEFAULT_DIRECTORY);
registryUrl = registryUrl.setProtocol(protocol).removeParameter(Constants.REGISTRY_KEY);
}
// zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&export=dubbo://192.168.20.218:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&default.accepts=1000&default.threadpool=fixed&default.threads=100&default.timeout=5000&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&owner=uce&pid=12028&side=provider&timestamp=1531912729429&owner=uce&pid=12028&timestamp=1531912729343
return registryFactory.getRegistry(registryUrl);
}

上面代码的意思是：

1.获取originalInvoker中的URL信息 (注册中心的配置信息)

2.将URL中信息中Param中registry参数获取到，并替换URL中的protocol属性，并删除Param中的registry信息，上面代码中的注释为执行前和执行后的的结果。

3.获取protocol 为 zookeeper对应的RegistryFactory接口的扩展对象 ZookeeperRegistryFactory 并执行getRegistry 方法：

ZookeeperRegistryFactory的继承结构和对应类中属性如下图所示：

其中REGISTRIES = new ConcurrentHashMap<String, Registry>(); 代表注册中心的配置，其中可以有多个注册中心配置

AbstractRegistryFactory.getRegistry执行代码如下：

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(); // zookeeper://192.168.1.157:2181/com.alibaba.dubbo.registry.RegistryService
// 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;
}
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();
}
}

1.设置Path属性，添加interface参数信息，及移除export 和 refer 参数信息。执行结果如下：

zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&interface=com.alibaba.dubbo.registry.RegistryService&owner=uce&pid=12028&timestamp=1531912729343

2.获取url对应的serviceString信息：zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService，由于我使用的是本地的zookeeper 所以IP为 127.0.0.1

3.顺序地创建注册中心：Registry ZookeeperRegistryFactory.createRegistry(URL url);

public Registry createRegistry(URL url) {
return new ZookeeperRegistry(url, zookeeperTransporter);
}
// 构造ZookeeperRegistry的调用链如下所示
public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) {
super(url);
if (url.isAnyHost()) {
throw new IllegalStateException(“registry address == null”);
}
String group = url.getParameter(Constants.GROUP_KEY, DEFAULT_ROOT);
if (!group.startsWith(Constants.PATH_SEPARATOR)) {
group = Constants.PATH_SEPARATOR group;
}
this.root = group;
zkClient = zookeeperTransporter.connect(url);
zkClient.addStateListener(new StateListener() {
public void stateChanged(int state) {
if (state == RECONNECTED) {
try {
recover();
} catch (Exception e) {
logger.error(e.getMessage(), e);
}
}
}
});
}
public FailbackRegistry(URL url) {
super(url);
int retryPeriod = url.getParameter(Constants.REGISTRY_RETRY_PERIOD_KEY, Constants.DEFAULT_REGISTRY_RETRY_PERIOD);
this.retryFuture = retryExecutor.scheduleWithFixedDelay(new Runnable() {
public void run() {
// 检测并连接注册中心
try {
retry();
} catch (Throwable t) { // 防御性容错
logger.error(“Unexpected error occur at failed retry, cause: ” t.getMessage(), t);
}
}
}, retryPeriod, retryPeriod, TimeUnit.MILLISECONDS);
}
public AbstractRegistry(URL url) {
setUrl(url);
// 启动文件保存定时器
syncSaveFile = url.getParameter(Constants.REGISTRY_FILESAVE_SYNC_KEY, false);
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;
loadProperties();
notify(url.getBackupUrls());
}

ZookeeperRegistry 的类继承结构图如图所示：

ZooKeeperRegistry.FailbackRegistry.AbstractRegistry中

1.setUrl设置url属性信息

2.是否启用文件的异步保存

3.注册中心对应的本地文件保存的位置信息：如C:/Users/Administrator/.dubbo/dubbo-registry-127.0.0.1.cache

4.给file赋值 并且加载文件信息到properties属性中

5.notify(url.getBackupUrls) 这段代码不知道什么意思。

ZooKeeperRegistry.FailbackRegistry中

1.获取定时任务的时间间隔。

2.开启定时任务定时检测失败的注册，并重新注册。

ZooKeeperRegistry 中

1.获取注册中心的group参数 ，默认为/dubbo , 并未root赋予group值

2.zkClient = zookeeperTransporter.connect(url); 链接zookeeper信息并添加状态监听事件，具体再更文详述吧，代码如下：

public ZkclientZookeeperClient(URL url) {
super(url);
client = new ZkClient(url.getBackupAddress());
client.subscribeStateChanges(new IZkStateListener() {
@Override
public void handleStateChanged(KeeperState state) throws Exception {
ZkclientZookeeperClient.this.state = state;
if (state == KeeperState.Disconnected) {
stateChanged(StateListener.DISCONNECTED);
} else if (state == KeeperState.SyncConnected) {
stateChanged(StateListener.CONNECTED);
}
}
@Override
public void handleNewSession() throws Exception {
stateChanged(StateListener.RECONNECTED);
}
});
}

3.添加重连状态的状态监听事件 调用 recover()方法。

至此 ZookeeperRegistry创建完毕。

ZookeeperRegistryFactory中最后将registry放入 ZookeeperRegistryFactory.REGISTRIES中

key 为zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService

value 为之前创建的ZookeeperRegistry对象。

接着返回RegistryProtocol 的export方法 ，

1.上面说到了调用doLocalExport(originInvoker);进行服务暴露的过程及调用getRegistry(originInvoker)方法通过ZookeeperRegistryFactory 工厂生成 ZookeeperRegistry 方法，然后加入到工厂REGISTRIES 缓存中，并返回ZookeeperRegistry 实例的过程。

2.接下来RegistryProtocol 的export方法中调用 final URL registedProviderUrl = getRegistedProviderUrl(originInvoker); 获取服务提供者的URL信息 ， 它是从注册中心的URL中获得export参数对应的值转换的URL信息。（去除掉不需要在注册中心上看到的字段）

3.接下来调用registry.register(registedProviderUrl); 进行服务的注册将暴露的服务信息注册到注册中心，并且将已经注册的服务URL缓存到ZookeeperRegistry.registered 已注册服务的缓存中。

FailbackRegistry.register
/**
* 进行服务注册逻辑的实现
*/
@Override
public void register(URL url) {
if (destroyed.get()){
return;
}
// 调用AbstractRegistry.register进行服务对应URL的缓存
super.register(url);
failedRegistered.remove(url);
failedUnregistered.remove(url);
try {
// 向服务器端发送注册请求，将服务注册到注册中心，可以使用各个注册协议(注册中心)的实现 此处使用zookeeper ZookeeperRegistry.doRegister
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);
}
}
AbstractRegistry.register
public void register(URL url) {
if (url == null) {
throw new IllegalArgumentException(“register url == null”);
}
if (logger.isInfoEnabled()) {
logger.info(“Register: ” url);
}
// 缓存已经注册的服务
registered.add(url);
}
ZookeeperRegistry.doRegister
protected void doRegister(URL url) {
try {
// 此处为具体服务暴露的代码 toUrlPath 根据URL生成写入zk的路径信息
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);
}
}

4.由registryProviderUrl获取overrideSubscribeUrl 再构建OverrideListener