motan源码分析一：服务发布及注册
motan是新浪微博开源的服务治理框架，具体介绍请看：http://tech.sina.com.cn/i/2016-05-10/doc-ifxryhhh1869879.shtml.
本系列的文章将分析它的底层源码，分析的源码版本为：0.1.2。第一篇文章将以服务的发布和注册开始，注册服务使用zookeeper来分析。源码地址：https://github.com/weibocom/motan
本文涉及到的主要类和接口：MotanApiExportDemo、MotanDemoService、MotanDemoServiceImpl、ServiceConfig、RegistryConfig、ProtocolConfig、DefaultProvider、ZookeeperRegistryFactory、ZookeeperRegistry、SimpleConfigHandler、ProtocolFilterDecorator等。
1.首先来看demo源码：MotanApiExportDemo
demo中先后创建了ServiceConfig、RegistryConfig和ProtocolConfig相关的对象，其中ServiceConfig是我们提供服务的相关配置(每个服务一个配置，例如一个服务接口一个配置，本文中的具体服务是：MotanDemoServiceImpl)、RegistryConfig是注册中心相关的配置信息、ProtocolConfig是应用协议相关的配置(在客户端还负责集群相关的配置)。
ServiceConfig<MotanDemoService> motanDemoService = new ServiceConfig<MotanDemoService>();
// 设置接口及实现类
motanDemoService.setInterface(MotanDemoService.class);//设置服务接口，客户端在rpc调用时，会在协议中传递接口名称，从而实现与具体实现类一一对应
motanDemoService.setRef(new MotanDemoServiceImpl());//设置接口实现类，实际的业务代码
// 配置服务的group以及版本号
motanDemoService.setGroup("motan-demo-rpc");//服务所属的组
motanDemoService.setVersion("1.0");
// 配置ZooKeeper注册中心
RegistryConfig zookeeperRegistry = new RegistryConfig();
zookeeperRegistry.setRegProtocol("zookeeper");//使用zookeeper作为注册中心
zookeeperRegistry.setAddress("127.0.0.1:2181");//zookeeper的连接地址
motanDemoService.setRegistry(zookeeperRegistry);
// 配置RPC协议
ProtocolConfig protocol = new ProtocolConfig();
protocol.setId("motan");//使用motan应用协议
protocol.setName("motan");
motanDemoService.setProtocol(protocol);
motanDemoService.setExport("motan:8010");//本服务的监控端口号是8010
motanDemoService.export();//发布及在zookeeper上注册此服务
2.从上面的代码可知ServiceConfig类是服务的发布及注册的核心是motanDemoService.export()方法，我们来看一下此方法的实现细节:
public synchronized void export()
{
if(exported.get())
{
LoggerUtil.warn(String.format("%s has already been expoted, so ignore the export request!", new Object[] {
interfaceClass.getName()
}));
return;
}
checkInterfaceAndMethods(interfaceClass, methods);
List registryUrls = loadRegistryUrls();//加载注册中心的url,支持多个注册中心
if(registryUrls == null || registryUrls.size() == 0)
throw new IllegalStateException((new StringBuilder("Should set registry config for service:")).append(interfaceClass.getName()).toString());
Map protocolPorts = getProtocolAndPort();
ProtocolConfig protocolConfig;
Integer port;
for(Iterator iterator = protocols.iterator(); iterator.hasNext(); doExport(protocolConfig, port.intValue(), registryUrls))//发布服务
{
protocolConfig = (ProtocolConfig)iterator.next();
port = (Integer)protocolPorts.get(protocolConfig.getId());
if(port == null)
throw new MotanServiceException(String.format("Unknow port in service:%s, protocol:%s", new Object[] {
interfaceClass.getName(), protocolConfig.getId()
}));
}
afterExport();
}
方法中调用了doexport和afterExport方法：
private void doExport(ProtocolConfig protocolConfig, int port, List registryURLs) { String protocolName = protocolConfig.getName();//获取协议名称，此处为motan if(protocolName == null || protocolName.length() == 0) protocolName = URLParamType.protocol.getValue(); String hostAddress = host;//本机地址 if(StringUtils.isBlank(hostAddress) && basicServiceConfig != null) hostAddress = basicServiceConfig.getHost(); if(NetUtils.isInvalidLocalHost(hostAddress)) hostAddress = getLocalHostAddress(registryURLs); Map map = new HashMap(); map.put(URLParamType.nodeType.getName(), "service"); map.put(URLParamType.refreshTimestamp.getName(), String.valueOf(System.currentTimeMillis())); collectConfigParams(map, new AbstractConfig[] { protocolConfig, basicServiceConfig, extConfig, this }); collectMethodConfigParams(map, getMethods()); URL serviceUrl = new URL(protocolName, hostAddress, port, interfaceClass.getName(), map);//组装serviceUrl信息 if(serviceExists(serviceUrl))//判断服务之前是否已经加载过 { LoggerUtil.warn(String.format("%s configService is malformed, for same service (%s) already exists ", new Object[] { interfaceClass.getName(), serviceUrl.getIdentity() })); throw new MotanFrameworkException(String.format("%s configService is malformed, for same service (%s) already exists ", new Object[] { interfaceClass.getName(), serviceUrl.getIdentity() }), MotanErrorMsgConstant.FRAMEWORK_INIT_ERROR);//抛出同名服务异常 } List urls = new ArrayList(); if("injvm".equals(protocolConfig.getId())) { URL localRegistryUrl = null; for(Iterator iterator2 = registryURLs.iterator(); iterator2.hasNext();) { URL ru = (URL)iterator2.next(); if("local".equals(ru.getProtocol())) { localRegistryUrl = ru.createCopy(); break; } } if(localRegistryUrl == null) localRegistryUrl = new URL("local", hostAddress, 0, com/weibo/api/motan/registry/RegistryService.getName()); urls.add(localRegistryUrl); } else { URL ru; for(Iterator iterator = registryURLs.iterator(); iterator.hasNext(); urls.add(ru.createCopy())) ru = (URL)iterator.next(); } URL u; for(Iterator iterator1 = urls.iterator(); iterator1.hasNext(); registereUrls.add(u.createCopy())) { u = (URL)iterator1.next(); u.addParameter(URLParamType.embed.getName(), StringTools.urlEncode(serviceUrl.toFullStr())); } ConfigHandler configHandler = (ConfigHandler)ExtensionLoader.getExtensionLoader(com/weibo/api/motan/config/handler/ConfigHandler).getExtension("default");//使用spi机制加载SimpleConfigHandler exporters.add(configHandler.export(interfaceClass, ref, urls));//调用SimpleConfigHandler的export方法 initLocalAppInfo(serviceUrl); } private void afterExport() { exported.set(true); Exporter ep; for(Iterator iterator = exporters.iterator(); iterator.hasNext(); existingServices.add(ep.getProvider().getUrl().getIdentity())) ep = (Exporter)iterator.next(); }
再来看一下SimpleConfigHandler的export方法
public <T> Exporter<T> export(Class<T> interfaceClass, T ref, List<URL> registryUrls) {
String serviceStr = StringTools.urlDecode(registryUrls.get(0).getParameter(URLParamType.embed.getName()));
URL serviceUrl = URL.valueOf(serviceStr);
// export service
// 利用protocol decorator来增加filter特性
String protocolName = serviceUrl.getParameter(URLParamType.protocol.getName(), URLParamType.protocol.getValue());
Protocol protocol = new ProtocolFilterDecorator(ExtensionLoader.getExtensionLoader(Protocol.class).getExtension(protocolName));//对于Protoclo对象增强filter
Provider<T> provider = new DefaultProvider<T>(ref, serviceUrl, interfaceClass);服务的代理提供者，包装ref的服务
Exporter<T> exporter = protocol.export(provider, serviceUrl);//发布服务，将代理对象provider与具体的serviceUrl关联
// register service
register(registryUrls, serviceUrl);
return exporter;
}
3.下面我们来看一下，motan如何对filter进行相应的增强处理
public class ProtocolFilterDecorator implements Protocol { //实现Protocol的接口，联系到上文中使用此类对实际的Protocol进行包装
private Protocol protocol;
public ProtocolFilterDecorator(Protocol protocol) {
if (protocol == null) {
throw new MotanFrameworkException("Protocol is null when construct ProtocolFilterDecorator",
MotanErrorMsgConstant.FRAMEWORK_INIT_ERROR);
}
this.protocol = protocol;//给实际的Protocol进行赋值
}
@Override
public <T> Exporter<T> export(Provider<T> provider, URL url) {
return protocol.export(decorateWithFilter(provider, url), url);发布服务时，调用filter增强处理方法
}
private <T> Provider<T> decorateWithFilter(Provider<T> provider, URL url) {
List<Filter> filters = getFilters(url, MotanConstants.NODE_TYPE_SERVICE);//获取实际需要增强的filter
if (filters == null || filters.size() == 0) {
return provider;
}
Provider<T> lastProvider = provider;
for (Filter filter : filters) {//对于代理对象provider进行包装，包装成一个provider链，返回最后一个provider
final Filter f = filter;
final Provider<T> lp = lastProvider;
lastProvider = new Provider<T>() {
@Override
public Response call(Request request) {
return f.filter(lp, request);//对于后面调用的call方法时，首先调用最外层的filter,最后再调用实际的provider的call方法
}
@Override
public String desc() {
return lp.desc();
}
@Override
public void destroy() {
lp.destroy();
}
@Override
public Class<T> getInterface() {
return lp.getInterface();
}
@Override
public URL getUrl() {
return lp.getUrl();
}
@Override
public void init() {
lp.init();
}
@Override
public boolean isAvailable() {
return lp.isAvailable();
}
};
}
return lastProvider;
}
private List<Filter> getFilters(URL url, String key) {
// load default filters
List<Filter> filters = new ArrayList<Filter>();
List<Filter> defaultFilters = ExtensionLoader.getExtensionLoader(Filter.class).getExtensions(key);//使用spi机制初始化filer对象
if (defaultFilters != null && defaultFilters.size() > 0) {
filters.addAll(defaultFilters);
}
// add filters via "filter" config
String filterStr = url.getParameter(URLParamType.filter.getName());
if (StringUtils.isNotBlank(filterStr)) {
String[] filterNames = MotanConstants.COMMA_SPLIT_PATTERN.split(filterStr);
for (String fn : filterNames) {
addIfAbsent(filters, fn);
}
}
// add filter via other configs, like accessLog and so on
boolean accessLog = url.getBooleanParameter(URLParamType.accessLog.getName(), URLParamType.accessLog.getBooleanValue());
if (accessLog) {
addIfAbsent(filters, AccessLogFilter.class.getAnnotation(SpiMeta.class).name());
}
// sort the filters
Collections.sort(filters, new ActivationComparator<Filter>());
Collections.reverse(filters);
return filters;
}
}
4.服务发布完成后，需要像注册中心注册此服务
private void register(List<URL> registryUrls, URL serviceUrl) {
for (URL url : registryUrls) {//循环便利多个注册中心的信息
// 根据check参数的设置，register失败可能会抛异常，上层应该知晓
RegistryFactory registryFactory = ExtensionLoader.getExtensionLoader(RegistryFactory.class).getExtension(url.getProtocol());//文中使用的是zookeeper
if (registryFactory == null) {
throw new MotanFrameworkException(new MotanErrorMsg(500, MotanErrorMsgConstant.FRAMEWORK_REGISTER_ERROR_CODE,
"register error! Could not find extension for registry protocol:" + url.getProtocol()
+ ", make sure registry module for " + url.getProtocol() + " is in classpath!"));
}
Registry registry = registryFactory.getRegistry(url);//获取registry
registry.register(serviceUrl);//将服务注册到zookeeper，也就是把节点信息写入到zookeeper中
}
}
我们来看一下zookeeper注册中心的工厂类：每个Registry都需要独立维护一个ZkClient与zookeeper的链接
@SpiMeta(name = "zookeeper")
public class ZookeeperRegistryFactory extends AbstractRegistryFactory {
@Override
protected Registry createRegistry(URL registryUrl) {
try {
int timeout = registryUrl.getIntParameter(URLParamType.connectTimeout.getName(), URLParamType.connectTimeout.getIntValue());
int sessionTimeout =
registryUrl.getIntParameter(URLParamType.registrySessionTimeout.getName(),
URLParamType.registrySessionTimeout.getIntValue());
ZkClient zkClient = new ZkClient(registryUrl.getParameter("address"), sessionTimeout, timeout);//创建zookeeper的客户端
return new ZookeeperRegistry(registryUrl, zkClient);//创建实际的Registry
} catch (ZkException e) {
LoggerUtil.error("[ZookeeperRegistry] fail to connect zookeeper, cause: " + e.getMessage());
throw e;
}
}
}
我们再来分析ZookeeperRegistry中的代码
public ZookeeperRegistry(URL url, ZkClient client) { super(url); this.zkClient = client; IZkStateListener zkStateListener = new IZkStateListener() { @Override public void handleStateChanged(Watcher.Event.KeeperState state) throws Exception { // do nothing } @Override public void handleNewSession() throws Exception {//响应zkClient的事件 LoggerUtil.info("zkRegistry get new session notify."); reconnectService();//重新注册服务 reconnectClient(); } }; zkClient.subscribeStateChanges(zkStateListener); } private void reconnectService() { Collection<URL> allRegisteredServices = getRegisteredServiceUrls(); if (allRegisteredServices != null && !allRegisteredServices.isEmpty()) { try { serverLock.lock(); for (URL url : getRegisteredServiceUrls()) { doRegister(url);//注册 } LoggerUtil.info("[{}] reconnect: register services {}", registryClassName, allRegisteredServices); for (URL url : availableServices) { if (!getRegisteredServiceUrls().contains(url)) { LoggerUtil.warn("reconnect url not register. url:{}", url); continue; } doAvailable(url);//标识服务可以提供服务 } LoggerUtil.info("[{}] reconnect: available services {}", registryClassName, availableServices); } finally { serverLock.unlock(); } } } protected void doRegister(URL url) { try { serverLock.lock(); // 防止旧节点未正常注销 removeNode(url, ZkNodeType.AVAILABLE_SERVER); removeNode(url, ZkNodeType.UNAVAILABLE_SERVER); createNode(url, ZkNodeType.UNAVAILABLE_SERVER); } catch (Throwable e) { throw new MotanFrameworkException(String.format("Failed to register %s to zookeeper(%s), cause: %s", url, getUrl(), e.getMessage()), e); } finally { serverLock.unlock(); } } protected void doAvailable(URL url) { try{ serverLock.lock(); if (url == null) { availableServices.addAll(getRegisteredServiceUrls()); for (URL u : getRegisteredServiceUrls()) { removeNode(u, ZkNodeType.AVAILABLE_SERVER); removeNode(u, ZkNodeType.UNAVAILABLE_SERVER); createNode(u, ZkNodeType.AVAILABLE_SERVER); } } else { availableServices.add(url); removeNode(url, ZkNodeType.AVAILABLE_SERVER); removeNode(url, ZkNodeType.UNAVAILABLE_SERVER); createNode(url, ZkNodeType.AVAILABLE_SERVER); } } finally { serverLock.unlock(); } }
private void createNode(URL url, ZkNodeType nodeType) {
String nodeTypePath = ZkUtils.toNodeTypePath(url, nodeType);
if (!zkClient.exists(nodeTypePath)) {
zkClient.createPersistent(nodeTypePath, true);//对于服务的标识信息，创建持久化节点
}
zkClient.createEphemeral(ZkUtils.toNodePath(url, nodeType), url.toFullStr());//对于服务的ip和端口号信息使用临时节点，当服务断了后，zookeeper自动摘除目标服务器
}
本文分析了motan的服务发布及注册到zookeeper的流程相关的源码，主要涉及到的知识点：
1.利用相关的配置对象进行信息的存储及传递；
2.利用provider对具体的业务类进行封装代理；
3.利用filter链的结构，来包装实际的provider，把所有的过滤器都处理完毕后，最后调用实际的业务类，大家可以想象一下aop相关的原理，有些类似；
4.代码中大量使用jdk的标准spi技术进行类的加载；
5.支持多个注册中心，也就是同一个服务可以注册到不同的注册中心上，每个registry对应一个具体的zkclient；
6.利用了zookeeper的临时节点来维护服务器的host和port信息；
7.支持多个服务发布到同一个端口，在本文中并没分析netty使用相关的代码，后面会分析到。
