Dubbo源码分析之服务注册原理
getRegistry
1. 把url转化为对应配置的注册中心的具体协议
2. 根据具体协议，从registryFactory中获得指定的注册中心实现
那么这个registryFactory具体是怎么赋值的呢？
final URL registeredProviderUrl = getRegisteredProviderUrl(providerUrl,
registryUrl);
ProviderInvokerWrapper<T> providerInvokerWrapper =
ProviderConsumerRegTable.registerProvider(originInvoker,
registryUrl, registeredProviderUrl);
//to judge if we need to delay publish
boolean register = registeredProviderUrl.getParameter("register", true);
if (register) {
register(registryUrl, registeredProviderUrl);
providerInvokerWrapper.setReg(true);
}
// Deprecated! Subscribe to override rules in 2.6.x or before.
registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
exporter.setRegisterUrl(registeredProviderUrl);
exporter.setSubscribeUrl(overrideSubscribeUrl);
//Ensure that a new exporter instance is returned every time export
return new DestroyableExporter<>(exporter);
}
// url to registry
final Registry registry = getRegistry(originInvoker);
final URL registeredProviderUrl = getRegisteredProviderUrl(providerUrl,
registryUrl);
ProviderInvokerWrapper<T> providerInvokerWrapper =
ProviderConsumerRegTable.registerProvider(originInvoker,
registryUrl, registeredProviderUrl);
//to judge if we need to delay publish
boolean register = registeredProviderUrl.getParameter("register", true);
if (register) {
register(registryUrl, registeredProviderUrl);
providerInvokerWrapper.setReg(true);
}private Registry getRegistry(final Invoker originInvoker) {
//把url转化为配置的具体协议，比如zookeeper://ip:port. 这样后续获得的注册中心就会是基于
zk的实现
URL registryUrl = getRegistryUrl(originInvoker);
return registryFactory.getRegistry(registryUrl);
}
在RegistryProtocol中存在一段这样的代码，很明显这是通过依赖注入来实现的扩展点。
private RegistryFactory registryFactory;
public void setRegistryFactory(RegistryFactory registryFactory) {
this.registryFactory = registryFactory;
}
按照扩展点的加载规则，我们可以先看看/META-INF/dubbo/internal路径下找到RegistryFactory的配
置文件.这个factory有多个扩展点的实现。
dubbo=org.apache.dubbo.registry.dubbo.DubboRegistryFactory
multicast=org.apache.dubbo.registry.multicast.MulticastRegistryFactory
zookeeper=org.apache.dubbo.registry.zookeeper.ZookeeperRegistryFactory
redis=org.apache.dubbo.registry.redis.RedisRegistryFactory
consul=org.apache.dubbo.registry.consul.ConsulRegistryFactory
etcd3=org.apache.dubbo.registry.etcd.EtcdRegistryFactory
接着，找到RegistryFactory的实现, 发现它里面有一个自适应的方法，根据url中protocol传入的值进行
适配
@SPI("dubbo")
public interface RegistryFactory {
@Adaptive({"protocol"})
Registry getRegistry(URL url);
RegistryFactory$Adaptive
由于在前面的代码中，url中的protocol已经改成了zookeeper，那么这个时候根据zookeeper获得的spi
扩展点应该是ZookeeperRegistryFactoryZookeeperRegistryFactory
这个方法中并没有getRegistry方法，而是在父类AbstractRegistryFactory
从缓存REGISTRIES中，根据key获得对应的Registry
如果不存在，则创建Registry
import org.apache.dubbo.common.extension.ExtensionLoader;
public class RegistryFactory$Adaptive implements
org.apache.dubbo.registry.RegistryFactory {
public org.apache.dubbo.registry.Registry
getRegistry(org.apache.dubbo.common.URL arg0) {
if (arg0 == null) throw new IllegalArgumentException("url == null");
org.apache.dubbo.common.URL url = arg0;
String extName = ( url.getProtocol() == null ? "dubbo" :
url.getProtocol() );
if(extName == null) throw new IllegalStateException("Failed to get
extension (org.apache.dubbo.registry.RegistryFactory) name from url (" +
url.toString() + ") use keys([protocol])");
org.apache.dubbo.registry.RegistryFactory extension =
(org.apache.dubbo.registry.RegistryFactory)ExtensionLoader.getExtensionLoader(or
g.apache.dubbo.registry.RegistryFactory.class).getExtension(extName);
return extension.getRegistry(arg0);
}
}
public Registry getRegistry(URL url) {
url = URLBuilder.from(url)
.setPath(RegistryService.class.getName())
.addParameter(Constants.INTERFACE_KEY,
RegistryService.class.getName())
.removeParameters(Constants.EXPORT_KEY, Constants.REFER_KEY)
.build();
String key = url.toServiceStringWithoutResolving();
// Lock the registry access process to ensure a single instance of the
registry
LOCK.lock();
try {
Registry registry = REGISTRIES.get(key);
if (registry != null) {
return registry;
}
//创建注册中心
registry = createRegistry(url);
if (registry == null) {
throw new IllegalStateException("Can not create registry " +
url);
}
REGISTRIES.put(key, registry);
return registry;
} finally {
// Release the lock
LOCK.unlock();
}
}createRegistry
创建一个zookeeperRegistry，把url和zookeepertransporter作为参数传入。
zookeeperTransporter 这个属性也是基于依赖注入来赋值的，具体的流程就不再分析了，这个的值应
该是
CuratorZookeeperTransporter 表示具体使用什么框架来和zk产生连接
ZookeeperRegistry
这个方法中使用了CuratorZookeeperTransport来实现zk的连接
registry.register(registedProviderUrl);
继续往下分析，会调用registry.register去讲dubbo://的协议地址注册到zookeeper上
这个方法会调用FailbackRegistry类中的register. 为什么呢？因为ZookeeperRegistry这个类中并没有
register这个方法，但是他的父类FailbackRegistry中存在register方法，而这个类又重写了
AbstractRegistry类中的register方法。所以我们可以直接定位大FailbackRegistry这个类中的register方
法中
public Registry createRegistry(URL url) {
return new ZookeeperRegistry(url, zookeeperTransporter);
}
public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) {
super(url);
if (url.isAnyHost()) {
throw new IllegalStateException("registry address == null");
}
//获得group名称
String group = url.getParameter(Constants.GROUP_KEY, DEFAULT_ROOT);
if (!group.startsWith(Constants.PATH_SEPARATOR)) {
group = Constants.PATH_SEPARATOR + group;
}
this.root = group;
//产生一个zookeeper连接
zkClient = zookeeperTransporter.connect(url);
//添加zookeeper状态变化事件
zkClient.addStateListener(state -> {
if (state == StateListener.RECONNECTED) {
try {
recover();
} catch (Exception e) {
logger.error(e.getMessage(), e);
}
}
});
}