一.前言
本文讲服务发布与服务注册，服务提供者本地发布服务，然后向注册中心注册服务，将服务实现类以服务接口的形式提供出去，以便服务消费者从注册中心查阅并调用服务。
本文源码分析基于org.apache.dubbo:dubbo:2.7.2，服务端代码例子是上文的例子
如果没有Dubbo SPI的基础知识，建议先看Dubbo SPI，否则源码怎么跳转的将毫无头绪
Dubbo SPI：
二.服务发布
调用顺序
首先讲一下大致的服务发布的调用顺序图，蓝色方法不分析，主要是起一个netty服务
-org.apache.dubbo.config.spring.ServiceBean#onApplicationEvent
-org.apache.dubbo.config.ServiceConfig#export
-org.apache.dubbo.config.ServiceConfig#doExport
-org.apache.dubbo.config.ServiceConfig#doExportUrls
-org.apache.dubbo.config.ServiceConfig#doExportUrlsFor1Protocol
-org.apache.dubbo.rpc.proxy.javassist.JavassistProxyFactory#getInvoker
-org.apache.dubbo.registry.integration.RegistryProtocol#export
-org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol#export
-org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol#createServer
-org.apache.dubbo.remoting.exchange.Exchangers#bind(org.apache.dubbo.common.URL, org.apache.dubbo.remoting.exchange.ExchangeHandler)
-org.apache.dubbo.remoting.exchange.support.header.HeaderExchanger#bind
-org.apache.dubbo.remoting.Transporters#bind(org.apache.dubbo.common.URL, org.apache.dubbo.remoting.ChannelHandler...)
-org.apache.dubbo.remoting.transport.netty.NettyTransporter#bind
...
源码分析
1.org.apache.dubbo.config.spring.ServiceBean#onApplicationEvent，这个方法就不多说了，注释写的很详细了
1 /**
2 * ServiceBean实现了ApplicationListener接口
3 * 在IOC的容器的启动过程，当所有的bean都已经处理完成之后，spring ioc容器会发布ContextRefreshedEvent事件。
4 * 此处就是接收到事件处理的逻辑，开始服务发布之旅
5 *
6 * @param event
7 */
8 @Override
9 public void onApplicationEvent(ContextRefreshedEvent event) {
10 // 是否已发布 && 是否已经被取消发布
11 if (!isExported() && !isUnexported()) {
12 if (logger.isInfoEnabled()) {
13 logger.info("The service ready on spring started. service: " + getInterface());
14 }
15 // 发布
16 export();
17 }
18 }
2.org.apache.dubbo.config.ServiceConfig#export，这里的checkAndUpdateSubConfigs主要做的就是检测标签合法，检测各种对象是否为空，为空则创建。之后判断是否可以发布和是否需要延迟发布，需要则延迟再doExport
1 public synchronized void export() {
2 // 检测<dubbo:service>的interface是否合法
3 // 检查provider为空
4 // 检查各种对象是否为空，为空则创建
5 checkAndUpdateSubConfigs();
6 if (!shouldExport()) {
7 return;
8 }
9 // 是否延迟？
10 if (shouldDelay()) {
11 // 延迟
12 DELAY_EXPORT_EXECUTOR.schedule(this::doExport, getDelay(), TimeUnit.MILLISECONDS);
13 } else {
14 doExport();
15 }
16 }
3.org.apache.dubbo.config.ServiceConfig#doExport，注释写的很清楚，还是没有走到核心逻辑
1 protected synchronized void doExport() {
2 // 是否已经被取消发布
3 if (unexported) {
4 throw new IllegalStateException("The service " + interfaceClass.getName() + " has already unexported!");
5 }
6 // 是否已经发布，注意这个变量volatile修饰
7 if (exported) {
8 return;
9 }
10 exported = true;
11 if (StringUtils.isEmpty(path)) {
12 path = interfaceName;
13 }
14 doExportUrls();
15 }
4.org.apache.dubbo.config.ServiceConfig#doExportUrls，先加载要注册的url，然后遍历所有协议，发布服务并注册
1 @SuppressWarnings({"unchecked", "rawtypes"})
2 private void doExportUrls() {
3 // 加载要注册的url
4 // registry://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=dubbo-server&dubbo=2.5.3&pid=10516®istry=zookeeper×tamp=1559889491339
5 List<URL> registryURLs = loadRegistries(true);
6 // for循环每个协议，发布服务并注册到注册中心
7 for (ProtocolConfig protocolConfig : protocols) {
8 String pathKey = URL.buildKey(getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), group, version);
9 ProviderModel providerModel = new ProviderModel(pathKey, ref, interfaceClass);
10 ApplicationModel.initProviderModel(pathKey, providerModel);
11 doExportUrlsFor1Protocol(protocolConfig, registryURLs);
12 }
13 }
5.org.apache.dubbo.config.ServiceConfig#doExportUrlsFor1Protocol，看方法名字也知道，单一协议多导出服务。这个方法做的事情比较多，我这边拆成4个部分，第一部分、第二部分和第三部分都是在做填充map的事情，第三部分最后生成导出url。第四部分开始发布服务，里面会判断到底是发布服务并且注册到注册中心呢还是仅发布服务。
1 private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {
2 /** 第一部分开始 **/
3 String name = protocolConfig.getName();
4 // 为空或者为空字符串，默认dubbo协议
5 if (StringUtils.isEmpty(name)) {
6 name = DUBBO;
7 }
8
9 Map<String, String> map = new HashMap<String, String>();
10 map.put(SIDE_KEY, PROVIDER_SIDE);
11
12 appendRuntimeParameters(map);
13 appendParameters(map, metrics);
14 appendParameters(map, application);
15 appendParameters(map, module);
16 // remove 'default.' prefix for configs from ProviderConfig
17 // appendParameters(map, provider, Constants.DEFAULT_KEY);
18 appendParameters(map, provider);
19 appendParameters(map, protocolConfig);
20 appendParameters(map, this);
21 // 上面的代码就是将版本，方法，各种配置放到map里去
22 // 这里给出debug的时候的map对象
23 // map.toString() = {side=provider, application=dubbo-server, dubbo=2.5.3, pid=10554, interface=com.grimmjx.edu.HelloService, timeout=100, anyhost=true, timestamp=1559890675368}
24 /** 第一部分结束 **/
25
26 /** 第二部分开始 **/
27 // 这段if里做的事情主要是检测<dubbo:method> 标签中的配置信息，填充map
28 if (CollectionUtils.isNotEmpty(methods)) {
29 for (MethodConfig method : methods) {
30 // 添加MethodConfig到map中，key=方法名.属性 value=属性值
31 // ex sayHello.retries:2
32 appendParameters(map, method, method.getName());
33 String retryKey = method.getName() + ".retry";
34 if (map.containsKey(retryKey)) {
35 String retryValue = map.remove(retryKey);
36 if ("false".equals(retryValue)) {
37 map.put(method.getName() + ".retries", "0");
38 }
39 }
40
41 // 获取ArgumentConfig列表
42 List<ArgumentConfig> arguments = method.getArguments();
43 if (CollectionUtils.isNotEmpty(arguments)) {
44 for (ArgumentConfig argument : arguments) {
45 // convert argument type
46 if (argument.getType() != null && argument.getType().length() > 0) {
47 Method[] methods = interfaceClass.getMethods();
48 // visit all methods
49 if (methods != null && methods.length > 0) {
50 for (int i = 0; i < methods.length; i++) {
51 String methodName = methods[i].getName();
52 // target the method, and get its signature
53 if (methodName.equals(method.getName())) {
54 Class<?>[] argtypes = methods[i].getParameterTypes();
55 // one callback in the method
56 if (argument.getIndex() != -1) {
57 if (argtypes[argument.getIndex()].getName().equals(argument.getType())) {
58 // 添加ArgumentConfig信息到map中
59 appendParameters(map, argument, method.getName() + "." + argument.getIndex());
60 } else {
61 throw new IllegalArgumentException("Argument config error : the index attribute and type attribute not match :index :" + argument.getIndex() + ", type:" + argument.getType());
62 }
63 } else {
64 // multiple callbacks in the method
65 for (int j = 0; j < argtypes.length; j++) {
66 Class<?> argclazz = argtypes[j];
67 if (argclazz.getName().equals(argument.getType())) {
68 appendParameters(map, argument, method.getName() + "." + j);
69 if (argument.getIndex() != -1 && argument.getIndex() != j) {
70 throw new IllegalArgumentException("Argument config error : the index attribute and type attribute not match :index :" + argument.getIndex() + ", type:" + argument.getType());
71 }
72 }
73 }
74 }
75 }
76 }
77 }
78 } else if (argument.getIndex() != -1) {
79 appendParameters(map, argument, method.getName() + "." + argument.getIndex());
80 } else {
81 throw new IllegalArgumentException("Argument config must set index or type attribute.eg: <dubbo:argument index='0' .../> or <dubbo:argument type=xxx .../>");
82 }
83
84 }
85 }
86 } // end of methods for
87 }
88 /** 第二部分结束 **/
89
90 /** 第三部分开始 **/
91 if (ProtocolUtils.isGeneric(generic)) {
92 map.put(GENERIC_KEY, generic);
93 map.put(METHODS_KEY, ANY_VALUE);
94 } else {
95 String revision = Version.getVersion(interfaceClass, version);
96 if (revision != null && revision.length() > 0) {
97 map.put(REVISION_KEY, revision);
98 }
99
100 // 生成包装类
101 String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames();
102 // 添加方法到map中
103 if (methods.length == 0) {
104 logger.warn("No method found in service interface " + interfaceClass.getName());
105 map.put(METHODS_KEY, ANY_VALUE);
106 } else {
107 map.put(METHODS_KEY, StringUtils.join(new HashSet<String>(Arrays.asList(methods)), ","));
108 }
109 }
110
111 // 添加token
112 if (!ConfigUtils.isEmpty(token)) {
113 if (ConfigUtils.isDefault(token)) {
114 map.put(TOKEN_KEY, UUID.randomUUID().toString());
115 } else {
116 map.put(TOKEN_KEY, token);
117 }
118 }
119
120 // export service
121 // 此处map.toString() = {side=provider, application=dubbo-server, methods=hello, dubbo=2.5.3, pid=10554, interface=com.grimmjx.edu.HelloService, timeout=100, anyhost=true, timestamp=1559890675368}
122 String host = this.findConfigedHosts(protocolConfig, registryURLs, map);
123 Integer port = this.findConfigedPorts(protocolConfig, name, map);
124 // 此处url=dubbo://192.168.5.16:20880/com.grimmjx.edu.HelloService?anyhost=true&application=dubbo-server&dubbo=2.5.3&interface=com.grimmjx.edu.HelloService&methods=hello&pid=11917&side=provider&timeout=100×tamp=1559973693109
125 URL url = new URL(name, host, port, getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), map);
126 if (ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class).hasExtension(url.getProtocol())) {
127 url = ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
128 .getExtension(url.getProtocol()).getConfigurator(url).configure(url);
129 }
130 /** 第三部分结束 **/
131
132 /** 第四部分开始 **/
133 // 开始发布服务
134 String scope = url.getParameter(SCOPE_KEY);
135 // don't export when none is configured
136 // //配置为none不暴露
137 if (!SCOPE_NONE.equalsIgnoreCase(scope)) {
138
139 // export to local if the config is not remote (export to remote only when config is remote)
140 // 配置不是remote的情况下做本地暴露 (配置为remote，则表示只暴露远程服务)
141 if (!SCOPE_REMOTE.equalsIgnoreCase(scope)) {
142 exportLocal(url);
143 }
144 // export to remote if the config is not local (export to local only when config is local)
145 // 如果配置不是local则暴露为远程服务.(配置为local，则表示只暴露远程服务)
146 if (!SCOPE_LOCAL.equalsIgnoreCase(scope)) {
147 if (!isOnlyInJvm() && logger.isInfoEnabled()) {
148 logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url);
149 }
150 if (CollectionUtils.isNotEmpty(registryURLs)) {
151 // 发布服务
152 for (URL registryURL : registryURLs) {
153 //if protocol is only injvm ,not register
154 if (LOCAL_PROTOCOL.equalsIgnoreCase(url.getProtocol())) {
155 continue;
156 }
157 url = url.addParameterIfAbsent(DYNAMIC_KEY, registryURL.getParameter(DYNAMIC_KEY));
158 URL monitorUrl = loadMonitor(registryURL);
159 if (monitorUrl != null) {
160 url = url.addParameterAndEncoded(MONITOR_KEY, monitorUrl.toFullString());
161 }
162 if (logger.isInfoEnabled()) {
163 logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL);
164 }
165
166 // For providers, this is used to enable custom proxy to generate invoker
167 String proxy = url.getParameter(PROXY_KEY);
168 if (StringUtils.isNotEmpty(proxy)) {
169 registryURL = registryURL.addParameter(PROXY_KEY, proxy);
170 }
171
172 // 生成Invoker
173 // Invoker是十分重要的对象，可向它发起invoke调用
174 Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(EXPORT_KEY, url.toFullString()));
175 // 持有this和invoker
176 // 此处的invoker.getUrl()=registry://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=dubbo-server&dubbo=2.5.3&export=dubbo%3A%2F%2F192.168.5.16%3A20880%2Fcom.grimmjx.edu.HelloService%3Fanyhost%3Dtrue%26application%3Ddubbo-server%26dubbo%3D2.5.3%26interface%3Dcom.grimmjx.edu.HelloService%26methods%3Dhello%26pid%3D10738%26side%3Dprovider%26timeout%3D100%26timestamp%3D1559895851366&pid=10738®istry=zookeeper×tamp=1559895851283
177 DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
178
179 // 发布，并生成Exporter
180 Exporter<?> exporter = protocol.export(wrapperInvoker);
181 exporters.add(exporter);
182 }
183
184 // 没有注册中心，仅发布服务
185 } else {
186 Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, url);
187 DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
188
189 Exporter<?> exporter = protocol.export(wrapperInvoker);
190 exporters.add(exporter);
191 }
192 /**
193 * @since 2.7.0
194 * ServiceData Store
195 */
196 MetadataReportService metadataReportService = null;
197 if ((metadataReportService = getMetadataReportService()) != null) {
198 metadataReportService.publishProvider(url);
199 }
200 }
201 }
202 this.urls.add(url);
203 /** 第四部分结束 **/
204 }
6.org.apache.dubbo.registry.integration.RegistryProtocol#export，为什么是RegistryProtocol？注释里写的很清楚了，这里的url是registry://开头的。
1 public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
2 // 获取注册地址
3 URL registryUrl = getRegistryUrl(originInvoker);
4 // url to export locally
5 // 获取provider url
6 URL providerUrl = getProviderUrl(originInvoker);
7 // Subscribe the override data
8 // FIXME When the provider subscribes, it will affect the scene : a certain JVM exposes the service and call
9 // the same service. Because the subscribed is cached key with the name of the service, it causes the
10 // subscription information to cover.
11 final URL overrideSubscribeUrl = getSubscribedOverrideUrl(providerUrl);
12 final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
13 overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
14 // 要注册的url
15 providerUrl = overrideUrlWithConfig(providerUrl, overrideSubscribeListener);
16 //export invoker
17 // 导出服务
18 final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker, providerUrl);
19 // url to registry
....
38 }
之后上面调用顺序图的蓝色部分的代码不做分析，主要是创建一个NettyServer（默认）。可自行研究
三.服务注册
调用顺序
首先讲一下大致的服务注册的调用顺序图，我们只分析红色部分。
-org.apache.dubbo.registry.integration.RegistryProtocol#register
-org.apache.dubbo.registry.support.AbstractRegistryFactory#getRegistry
-org.apache.dubbo.registry.zookeeper.ZookeeperRegistryFactory#createRegistry
-org.apache.dubbo.registry.zookeeper.ZookeeperRegistry#ZookeeperRegistry
-org.apache.dubbo.registry.support.FailbackRegistry#register
-org.apache.dubbo.registry.zookeeper.ZookeeperRegistry#doRegister源码分析
1.org.apache.dubbo.registry.support.AbstractRegistryFactory#getRegistry，具体还要看下一步
1 @Override
2 public Registry getRegistry(URL url) {
3 url = URLBuilder.from(url)
4 .setPath(RegistryService.class.getName())
5 .addParameter(INTERFACE_KEY, RegistryService.class.getName())
6 .removeParameters(EXPORT_KEY, REFER_KEY)
7 .build();
8 String key = url.toServiceStringWithoutResolving();
9 // Lock the registry access process to ensure a single instance of the registry
10 LOCK.lock();
11 try {
12 // 缓存中获取
13 Registry registry = REGISTRIES.get(key);
14 if (registry != null) {
15 return registry;
16 }
17
18 //create registry by spi/ioc
19 // 用Dubbo SPI创建Registry
20 registry = createRegistry(url);
21 if (registry == null) {
22 throw new IllegalStateException("Can not create registry " + url);
23 }
24 // 写入缓存
25 REGISTRIES.put(key, registry);
26 return registry;
27 } finally {
28 // Release the lock
29 LOCK.unlock();
30 }
31 }
2.org.apache.dubbo.registry.zookeeper.ZookeeperRegistryFactory#createRegistry，创建一个ZooKeeperRegistry实例并返回
1 @Override
2 public Registry createRegistry(URL url) {
3 return new ZookeeperRegistry(url, zookeeperTransporter);
4 }
3.org.apache.dubbo.registry.zookeeper.ZookeeperRegistry#ZookeeperRegistry，主要做的就是利用zk创建Zk客户端
1 public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) {
2 super(url);
3 if (url.isAnyHost()) {
4 throw new IllegalStateException("registry address == null");
5 }
6 String group = url.getParameter(GROUP_KEY, DEFAULT_ROOT);
7 if (!group.startsWith(PATH_SEPARATOR)) {
8 group = PATH_SEPARATOR + group;
9 }
10 this.root = group;
11 zkClient = zookeeperTransporter.connect(url);
12 zkClient.addStateListener(state -> {
13 if (state == StateListener.RECONNECTED) {
14 try {
15 recover();
16 } catch (Exception e) {
17 logger.error(e.getMessage(), e);
18 }
19 }
20 });
21 }
4.org.apache.dubbo.registry.zookeeper.ZookeeperRegistry#doRegister，连接好zk后，是不是就要创建服务提供者的节点了？所以这一步就是注册服务
1 @Override
2 public void doRegister(URL url) {
3 try {
4 // toUrlPath(url) = /dubbo/com.grimmjx.edu.HelloService/providers/dubbo%3A%2F%2F192.168.5.16%3A20880%2Fcom.grimmjx.edu.HelloService%3Fanyhost%3Dtrue%26application%3Ddubbo-server%26dubbo%3D2.5.3%26interface%3Dcom.grimmjx.edu.HelloService%26methods%3Dhello%26pid%3D11917%26side%3Dprovider%26timeout%3D100%26timestamp%3D1559973693109
5 zkClient.create(toUrlPath(url), url.getParameter(DYNAMIC_KEY, true));
6 } catch (Throwable e) {
7 throw new RpcException("Failed to register " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);
8 }
9 }
这一步之后，我们用zkCli来连接zk看一下节点数据
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