dubbo源码分析-服务导出（二）

青旅半醒 2022-01-12 22:49 178阅读 0赞

[2019独角兽企业重金招聘Python工程师标准>>> ][2019_Python_] ![hot3.png][]

\#\# 创建注册中心

服务注册操作对于 Dubbo 来说不是必需的，通过服务直连的方式就可以绕过注册中心。但通常我们不会这么做，直连方式不利于服务治理，仅推荐在测试服务时使用。对于 Dubbo 来说，注册中心虽不是必需，但却是必要的。

在dubbo-config.xml配置注册中心，指定zookeeper作为注册中心实现方式

\`\`\`

<dubbo:registry protocol="zookeeper" address="${dubbo.registry.address}" check="false" port="${dubbo.protocol.port}">
        <dubbo:parameter key="qos.enable" value="false"/>
    </dubbo:registry>

\`\`\`

在RegistryProtocal中注册过程在export方法

\`\`\`

public <T> Exporter<T> export(Invoker<T> originInvoker) throws RpcException {
        RegistryProtocol.ExporterChangeableWrapper<T> exporter = this.doLocalExport(originInvoker);
        URL registryUrl = this.getRegistryUrl(originInvoker);
        Registry registry = this.getRegistry(originInvoker);
        URL registedProviderUrl = this.getRegistedProviderUrl(originInvoker);
        boolean register = registedProviderUrl.getParameter("register", true);
        ProviderConsumerRegTable.registerProvider(originInvoker, registryUrl, registedProviderUrl);
        //服务注册到注册中心
        if (register) {
            this.register(registryUrl, registedProviderUrl);
            ProviderConsumerRegTable.getProviderWrapper(originInvoker).setReg(true);
        }
    
        URL overrideSubscribeUrl = this.getSubscribedOverrideUrl(registedProviderUrl);
        RegistryProtocol.OverrideListener overrideSubscribeListener = new RegistryProtocol.OverrideListener(overrideSubscribeUrl, originInvoker);
        this.overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
        registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
        return new RegistryProtocol.DestroyableExporter(exporter, originInvoker, overrideSubscribeUrl, registedProviderUrl);
    }

\`\`\`

register方法如下

\`\`\`

public void register(URL registryUrl, URL registedProviderUrl) {
        Registry registry = this.registryFactory.getRegistry(registryUrl);
        registry.register(registedProviderUrl);
    }

\`\`\`

ResistryFactory的有多种实现

![a76ffd47ae011f6111e535307606bf41587.jpg][]

@SPI("dubbo")
    public interface RegistryFactory {
        @Adaptive({
       "protocol"})
        Registry getRegistry(URL var1);
    }

RegistryFactory接口是@SPI注解，如果未指定，默认使用dubbo作为注册中心

下面看下Zookeeper的实现

![ccb3f80302c9acd2d1a70b9e83e94e62825.jpg][]

ZookeeperRegistry继承AbstractRegistry类

\`\`\`

public abstract class AbstractRegistryFactory implements RegistryFactory {
        private static final Logger LOGGER = LoggerFactory.getLogger(AbstractRegistryFactory.class);
        private static final ReentrantLock LOCK = new ReentrantLock();
        private static final Map<String, Registry> REGISTRIES = new ConcurrentHashMap();
    
        public AbstractRegistryFactory() {
        }
    
        public static Collection<Registry> getRegistries() {
            return Collections.unmodifiableCollection(REGISTRIES.values());
        }
        //使用重入锁销毁注册中心
        public static void destroyAll() {
            if (LOGGER.isInfoEnabled()) {
                LOGGER.info("Close all registries " + getRegistries());
            }
    
            LOCK.lock();
    
            try {
                Iterator i$ = getRegistries().iterator();
    
                while(i$.hasNext()) {
                    Registry registry = (Registry)i$.next();
    
                    try {
                        registry.destroy();
                    } catch (Throwable var6) {
                        LOGGER.error(var6.getMessage(), var6);
                    }
                }
    
                REGISTRIES.clear();
            } finally {
                LOCK.unlock();
            }
        }
        //获取注册中心实例
        public Registry getRegistry(URL url) {
            url = url.setPath(RegistryService.class.getName()).addParameter("interface", RegistryService.class.getName()).removeParameters(new String[]{
       "export", "refer"});
            String key = url.toServiceString();
            LOCK.lock();
    
            Registry var4;
            try {
                Registry registry = (Registry)REGISTRIES.get(key);
                if (registry == null) {
                    registry = this.createRegistry(url);
                    if (registry == null) {
                        throw new IllegalStateException("Can not create registry " + url);
                    }
    
                    REGISTRIES.put(key, registry);
                    var4 = registry;
                    return var4;
                }
    
                var4 = registry;
            } finally {
                LOCK.unlock();
            }
    
            return var4;
        }
    
        protected abstract Registry createRegistry(URL var1);
    }

\`\`\`

createRegistry方法需要实现类重写

public class ZookeeperRegistry extends FailbackRegistry {
        private static final Logger logger = LoggerFactory.getLogger(ZookeeperRegistry.class);
        private static final int DEFAULT_ZOOKEEPER_PORT = 2181;
        private static final String DEFAULT_ROOT = "dubbo";
        private final String root;
        private final Set<String> anyServices = new ConcurrentHashSet();
        private final ConcurrentMap<URL, ConcurrentMap<NotifyListener, ChildListener>> zkListeners = new ConcurrentHashMap();
        private final ZookeeperClient zkClient;
    
        public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) {
            super(url);
            if (url.isAnyHost()) {
                throw new IllegalStateException("registry address == null");
            } else {
                //设置group 默认dubbo
                String group = url.getParameter("group", "dubbo");
                if (!group.startsWith("/")) {
                    group = "/" + group;
                }
    
                this.root = group;
                // 创建 Zookeeper 客户端
                this.zkClient = zookeeperTransporter.connect(url);
                // 添加状态监听器
                this.zkClient.addStateListener(new StateListener() {
                    public void stateChanged(int state) {
                        if (state == 2) {
                            try {
                                ZookeeperRegistry.this.recover();
                            } catch (Exception var3) {
                                ZookeeperRegistry.logger.error(var3.getMessage(), var3);
                            }
                        }
    
                    }
                });
            }
        }
    
        static String appendDefaultPort(String address) {
            if (address != null && address.length() > 0) {
                int i = address.indexOf(58);
                if (i < 0) {
                    return address + ":" + 2181;
                }
    
                if (Integer.parseInt(address.substring(i + 1)) == 0) {
                    return address.substring(0, i + 1) + 2181;
                }
            }
    
            return address;
        }
    
        public boolean isAvailable() {
            return this.zkClient.isConnected();
        }
    
        public void destroy() {
            super.destroy();
    
            try {
                this.zkClient.close();
            } catch (Exception var2) {
                logger.warn("Failed to close zookeeper client " + this.getUrl() + ", cause: " + var2.getMessage(), var2);
            }
    
        }
    
        protected void doRegister(URL url) {
            try {
                this.zkClient.create(this.toUrlPath(url), url.getParameter("dynamic", true));
            } catch (Throwable var3) {
                throw new RpcException("Failed to register " + url + " to zookeeper " + this.getUrl() + ", cause: " + var3.getMessage(), var3);
            }
        }
    
        protected void doUnregister(URL url) {
            try {
                this.zkClient.delete(this.toUrlPath(url));
            } catch (Throwable var3) {
                throw new RpcException("Failed to unregister " + url + " to zookeeper " + this.getUrl() + ", cause: " + var3.getMessage(), var3);
            }
        }
    
        protected void doSubscribe(final URL url, final NotifyListener listener) {
            try {
                if ("*".equals(url.getServiceInterface())) {
                    String root = this.toRootPath();
                    ConcurrentMap<NotifyListener, ChildListener> listeners = (ConcurrentMap)this.zkListeners.get(url);
                    if (listeners == null) {
                        this.zkListeners.putIfAbsent(url, new ConcurrentHashMap());
                        listeners = (ConcurrentMap)this.zkListeners.get(url);
                    }
    
                    ChildListener zkListener = (ChildListener)listeners.get(listener);
                    if (zkListener == null) {
                        listeners.putIfAbsent(listener, new ChildListener() {
                            public void childChanged(String parentPath, List<String> currentChilds) {
                                Iterator i$ = currentChilds.iterator();
    
                                while(i$.hasNext()) {
                                    String child = (String)i$.next();
                                    child = URL.decode(child);
                                    if (!ZookeeperRegistry.this.anyServices.contains(child)) {
                                        ZookeeperRegistry.this.anyServices.add(child);
                                        ZookeeperRegistry.this.subscribe(url.setPath(child).addParameters(new String[]{
       "interface", child, "check", String.valueOf(false)}), listener);
                                    }
                                }
    
                            }
                        });
                        zkListener = (ChildListener)listeners.get(listener);
                    }
    
                    this.zkClient.create(root, false);
                    List<String> services = this.zkClient.addChildListener(root, zkListener);
                    if (services != null && services.size() > 0) {
                        Iterator i$ = services.iterator();
    
                        while(i$.hasNext()) {
                            String service = (String)i$.next();
                            service = URL.decode(service);
                            this.anyServices.add(service);
                            this.subscribe(url.setPath(service).addParameters(new String[]{
       "interface", service, "check", String.valueOf(false)}), listener);
                        }
                    }
                } else {
                    List<URL> urls = new ArrayList();
                    String[] arr$ = this.toCategoriesPath(url);
                    int len$ = arr$.length;
    
                    for(int i$ = 0; i$ < len$; ++i$) {
                        String path = arr$[i$];
                        ConcurrentMap<NotifyListener, ChildListener> listeners = (ConcurrentMap)this.zkListeners.get(url);
                        if (listeners == null) {
                            this.zkListeners.putIfAbsent(url, new ConcurrentHashMap());
                            listeners = (ConcurrentMap)this.zkListeners.get(url);
                        }
    
                        ChildListener zkListener = (ChildListener)listeners.get(listener);
                        if (zkListener == null) {
                            listeners.putIfAbsent(listener, new ChildListener() {
                                public void childChanged(String parentPath, List<String> currentChilds) {
                                    ZookeeperRegistry.this.notify(url, listener, ZookeeperRegistry.this.toUrlsWithEmpty(url, parentPath, currentChilds));
                                }
                            });
                            zkListener = (ChildListener)listeners.get(listener);
                        }
    
                        this.zkClient.create(path, false);
                        List<String> children = this.zkClient.addChildListener(path, zkListener);
                        if (children != null) {
                            urls.addAll(this.toUrlsWithEmpty(url, path, children));
                        }
                    }
    
                    this.notify(url, listener, urls);
                }
    
            } catch (Throwable var11) {
                throw new RpcException("Failed to subscribe " + url + " to zookeeper " + this.getUrl() + ", cause: " + var11.getMessage(), var11);
            }
        }
    
        protected void doUnsubscribe(URL url, NotifyListener listener) {
            ConcurrentMap<NotifyListener, ChildListener> listeners = (ConcurrentMap)this.zkListeners.get(url);
            if (listeners != null) {
                ChildListener zkListener = (ChildListener)listeners.get(listener);
                if (zkListener != null) {
                    this.zkClient.removeChildListener(this.toUrlPath(url), zkListener);
                }
            }
    
        }
    
        public List<URL> lookup(URL url) {
            if (url == null) {
                throw new IllegalArgumentException("lookup url == null");
            } else {
                try {
                    List<String> providers = new ArrayList();
                    String[] arr$ = this.toCategoriesPath(url);
                    int len$ = arr$.length;
    
                    for(int i$ = 0; i$ < len$; ++i$) {
                        String path = arr$[i$];
                        List<String> children = this.zkClient.getChildren(path);
                        if (children != null) {
                            providers.addAll(children);
                        }
                    }
    
                    return this.toUrlsWithoutEmpty(url, providers);
                } catch (Throwable var8) {
                    throw new RpcException("Failed to lookup " + url + " from zookeeper " + this.getUrl() + ", cause: " + var8.getMessage(), var8);
                }
            }
        }
    
        private String toRootDir() {
            return this.root.equals("/") ? this.root : this.root + "/";
        }
    
        private String toRootPath() {
            return this.root;
        }
    
        private String toServicePath(URL url) {
            String name = url.getServiceInterface();
            return "*".equals(name) ? this.toRootPath() : this.toRootDir() + URL.encode(name);
        }
    
        private String[] toCategoriesPath(URL url) {
            String[] categroies;
            if ("*".equals(url.getParameter("category"))) {
                categroies = new String[]{
       "providers", "consumers", "routers", "configurators"};
            } else {
                categroies = url.getParameter("category", new String[]{
       "providers"});
            }
    
            String[] paths = new String[categroies.length];
    
            for(int i = 0; i < categroies.length; ++i) {
                paths[i] = this.toServicePath(url) + "/" + categroies[i];
            }
    
            return paths;
        }
    
        private String toCategoryPath(URL url) {
            return this.toServicePath(url) + "/" + url.getParameter("category", "providers");
        }
    
        private String toUrlPath(URL url) {
            return this.toCategoryPath(url) + "/" + URL.encode(url.toFullString());
        }
    
        private List<URL> toUrlsWithoutEmpty(URL consumer, List<String> providers) {
            List<URL> urls = new ArrayList();
            if (providers != null && providers.size() > 0) {
                Iterator i$ = providers.iterator();
    
                while(i$.hasNext()) {
                    String provider = (String)i$.next();
                    provider = URL.decode(provider);
                    if (provider.contains("://")) {
                        URL url = URL.valueOf(provider);
                        if (UrlUtils.isMatch(consumer, url)) {
                            urls.add(url);
                        }
                    }
                }
            }
    
            return urls;
        }
    
        private List<URL> toUrlsWithEmpty(URL consumer, String path, List<String> providers) {
            List<URL> urls = this.toUrlsWithoutEmpty(consumer, providers);
            if (urls == null || urls.isEmpty()) {
                int i = path.lastIndexOf(47);
                String category = i < 0 ? path : path.substring(i + 1);
                URL empty = consumer.setProtocol("empty").addParameter("category", category);
                urls.add(empty);
            }
    
            return urls;
        }
    }

下面分析CuratorZookeeperClient实现

public CuratorZookeeperClient(URL url) {
        super(url);
    
        try {
             // 创建 CuratorFramework 构造器 
            Builder builder = CuratorFrameworkFactory.builder().connectString(url.getBackupAddress()).retryPolicy(new RetryNTimes(1, 1000)).connectionTimeoutMs(5000);
            String authority = url.getAuthority();
            if (authority != null && authority.length() > 0) {
                builder = builder.authorization("digest", authority.getBytes());
            }
             // 构建 CuratorFramework 实例 
            this.client = builder.build();
            this.client.getConnectionStateListenable().addListener(new ConnectionStateListener() {
                public void stateChanged(CuratorFramework client, ConnectionState state) {
                    if (state == ConnectionState.LOST) {
                        CuratorZookeeperClient.this.stateChanged(0);
                    } else if (state == ConnectionState.CONNECTED) {
                        CuratorZookeeperClient.this.stateChanged(1);
                    } else if (state == ConnectionState.RECONNECTED) {
                        CuratorZookeeperClient.this.stateChanged(2);
                    }
    
                }
            });
            this.client.start();
        } catch (Exception var4) {
            throw new IllegalStateException(var4.getMessage(), var4);
        }
    }

以 Zookeeper 为例，所谓的服务注册，本质上是将服务配置数据写入到 Zookeeper 的某个路径的节点下

\#\# 服务注册

用法

<dubbo:service  retries="0" interface="com.rbsn.tms.operatebill.service.WechatPayService"
                    ref="wechatPayService"/>

服务注册在FailbackRegistry类中

\`\`\`

public void register(URL url) {
        if (!this.destroyed.get()) {
            super.register(url);
            this.failedRegistered.remove(url);
            this.failedUnregistered.remove(url);
    
            try {
                //服务注册
                this.doRegister(url);
            } catch (Exception var6) {
                Throwable t = var6;
                // 获取 check 参数，若 check = true 将会直接抛出异常 
                boolean check = this.getUrl().getParameter("check", true) && url.getParameter("check", true) && !"consumer".equals(url.getProtocol());
                boolean skipFailback = var6 instanceof SkipFailbackWrapperException;
                if (check || skipFailback) {
                    if (skipFailback) {
                        t = var6.getCause();
                    }
    
                    throw new IllegalStateException("Failed to register " + url + " to registry " + this.getUrl().getAddress() + ", cause: " + ((Throwable)t).getMessage(), (Throwable)t);
                }
    
                this.logger.error("Failed to register " + url + ", waiting for retry, cause: " + var6.getMessage(), var6);
                this.failedRegistered.add(url);
            }
    
        }
    }

\`\`\`

doRegistry方法在ZookeeperResistry中, *通过 Zookeeper 客户端创建节点，节点路径由 toUrlPath 方法生成，*

*路径格式如下:**// /$\{group\}/$\{serviceInterface\}/providers/$\{url\}**// 比如**// /dubbo/org.apache.dubbo.DemoService/providers/dubbo%3A%2F%2F127.0.0.1......*

\`\`\`

protected void doRegister(URL url) {
        try {
            this.zkClient.create(this.toUrlPath(url), url.getParameter("dynamic", true));
        } catch (Throwable var3) {
            throw new RpcException("Failed to register " + url + " to zookeeper " + this.getUrl() + ", cause: " + var3.getMessage(), var3);
        }
    }

\`\`\`

create方法在AbstractZookeeperClient类中,ephemeral参数表示是否创建临时节点 默认true

\`\`\`

public void create(String path, boolean ephemeral) {
        int i = path.lastIndexOf(47);
        if (i > 0) {
            String parentPath = path.substring(0, i);
             // 如果要创建的节点类型非临时节点，那么这里要检测节点是否存在 
            if (!this.checkExists(parentPath)) {
                this.create(parentPath, false);
            }
        }
    
        if (ephemeral) {
            //创建临时节点
            this.createEphemeral(path);
        } else {
            //创建持久化节点
            this.createPersistent(path);
        }
    
    }

\`\`\`

通过递归创建当前节点的上一级路径，然后再根据 ephemeral 的值决定创建临时还是持久节点，createEphemeral方法实现如下

public void createEphemeral(String path) {
        try {
            ((ACLBackgroundPathAndBytesable)this.client.create().withMode(CreateMode.EPHEMERAL)).forPath(path);
        } catch (NodeExistsException var3) {
            ;
        } catch (Exception var4) {
            throw new IllegalStateException(var4.getMessage(), var4);
        }
    
    }

整个过程可简单总结为：先创建注册中心实例，之后再通过注册中心实例注册服务

转载于:https://my.oschina.net/odetteisgorgeous/blog/3018827

[2019_Python_]: https://my.oschina.net/u/2663968/blog/3061697
[hot3.png]: /images/20220112/c7307180b2dd4b4cae1da21ef3a96bbc.png
[a76ffd47ae011f6111e535307606bf41587.jpg]: /images/20220112/2fafa502c184445f97063bc3fed558b0.png
[ccb3f80302c9acd2d1a70b9e83e94e62825.jpg]: /images/20220112/e3a8daf1d8ae46ea8f695dea6294b44e.png