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。