Dubbo 源码分析 —— 调试环境搭建二

在《 Dubbo 源码分析 —— 调试环境搭建一》主要是Dubbo 的官方介绍，Dubbo 提供了 dubbo-demo 项目，用于开发者快速入门。先说下注册中心，官方推荐使用 Zookeeper 注册中心

1.Registry

Dubbo 提供了多种 Registry 的实现，参见《注册中心参考手册》。

在 dubbo-demo 项目中，使用 Multicast Registry 。实际生产环境中，使用 Zookeeper Registry 。

友情提示：「Multicast Registry」和「Zookeeper Registry」二选一，建议先使用前者搭建调试环境，因为简单方便。

Multicast Registry

Multicast Registry 基于组播协议实现，详细参见文档《Multicast 注册中心》。

Multicast 注册中心不需要启动任何中心节点，只要广播地址一样，就可以互相发现。

Multicast 注册中心不需要启动任何中心节点，只要广播地址一样，就可以互相发现。

Dubbo 源码分析 —— 调试环境搭建二

提供方启动时广播自己的地址
消费方启动时广播订阅请求
提供方收到订阅请求时，单播自己的地址给订阅者，如果设置了 unicast=false，则广播给订阅者
消费方收到提供方地址时，连接该地址进行 RPC 调用。

组播受网络结构限制，只适合小规模应用或开发阶段使用。组播地址段: 224.0.0.0 – 239.255.255.255

配置

<dubbo:registry address="multicast://224.5.6.7:1234" />

或

<dubbo:registry protocol="multicast" address="224.5.6.7:1234" />

为了减少广播量，Dubbo 缺省使用单播发送提供者地址信息给消费者，如果一个机器上同时启了多个消费者进程，消费者需声明 unicast=false，否则只会有一个消费者能收到消息：

<dubbo:registry address="multicast://224.5.6.7:1234?unicast=false" />

或

<dubbo:registry protocol="multicast" address="224.5.6.7:1234">
    <dubbo:parameter key="unicast" value="false" />
</dubbo:registry>

注意**，不需要启动！！！简单的说，本小节的内容可以直接跳过。

zookeeper 注册中心

Zookeeper Registry 基于 Zookeeper 实现，详细参见文档《zookeeper 注册中心》。

Zookeeper 是 Apacahe Hadoop 的子项目，是一个树型的目录服务，支持变更推送，适合作为 Dubbo 服务的注册中心，工业强度较高，可用于生产环境，并推荐使用 [1]。

Dubbo 源码分析 —— 调试环境搭建二

流程说明：

服务提供者启动时: 向 /dubbo/com.foo.BarService/providers 目录下写入自己的 URL 地址
服务消费者启动时: 订阅 /dubbo/com.foo.BarService/providers 目录下的提供者 URL 地址。并向 /dubbo/com.foo.BarService/consumers 目录下写入自己的 URL 地址
监控中心启动时: 订阅 /dubbo/com.foo.BarService 目录下的所有提供者和消费者 URL 地址。

支持以下功能：

当提供者出现断电等异常停机时，注册中心能自动删除提供者信息
当注册中心重启时，能自动恢复注册数据，以及订阅请求
当会话过期时，能自动恢复注册数据，以及订阅请求
当设置 <dubbo:registry check="false" /> 时，记录失败注册和订阅请求，后台定时重试
可通过 <dubbo:registry username="admin" password="1234" /> 设置 zookeeper 登录信息
可通过 <dubbo:registry group="dubbo" /> 设置 zookeeper 的根节点，不设置将使用无根树
支持 * 号通配符 <dubbo:reference group="*" version="*" />，可订阅服务的所有分组和所有版本的提供者

使用

在 provider 和 consumer 中增加 zookeeper 客户端 jar 包依赖：

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.3.3</version>
</dependency>

或直接下载。

Dubbo 支持 zkclient 和 curator 两种 Zookeeper 客户端实现：

使用 zkclient 客户端

从 2.2.0 版本开始缺省为 zkclient 实现，以提升 zookeeper 客户端的健状性。zkclient 是 Datameer 开源的一个 Zookeeper 客户端实现。

缺省配置：

<dubbo:registry ... client="zkclient" />

或：

dubbo.registry.client=zkclient

或：

zookeeper://10.20.153.10:2181?client=zkclient

需依赖或直接下载：

<dependency>
    <groupId>com.github.sgroschupf</groupId>
    <artifactId>zkclient</artifactId>
    <version>0.1</version>
</dependency>

使用 curator 客户端

从 2.3.0 版本开始支持可选 curator 实现。Curator 是 Netflix 开源的一个 Zookeeper 客户端实现。

如果需要改为 curator 实现，请配置：

<dubbo:registry ... client="curator" />

或：

dubbo.registry.client=curator

或：

zookeeper://10.20.153.10:2181?client=curator

需依赖或直接下载：

<dependency>
    <groupId>com.netflix.curator</groupId>
    <artifactId>curator-framework</artifactId>
    <version>1.1.10</version>
</dependency>

Zookeeper 单机配置:

<dubbo:registry address="zookeeper://10.20.153.10:2181" />

或：

<dubbo:registry protocol="zookeeper" address="10.20.153.10:2181" />

Zookeeper 集群配置：

<dubbo:registry address="zookeeper://10.20.153.10:2181?backup=10.20.153.11:2181,10.20.153.12:2181" />

或：

<dubbo:registry protocol="zookeeper" address="10.20.153.10:2181,10.20.153.11:2181,10.20.153.12:2181" />

同一 Zookeeper，分成多组注册中心:

<dubbo:registry id="chinaRegistry" protocol="zookeeper" address="10.20.153.10:2181" group="china" />
<dubbo:registry id="intlRegistry" protocol="zookeeper" address="10.20.153.10:2181" group="intl" />

zookeeper 安装

安装方式参见: Zookeeper安装手册，只需搭一个原生的 Zookeeper 服务器，并将 Quick Start 中 Provider 和 Consumer 里的 conf/dubbo.properties 中的 dubbo.registry.addrss 的值改为 zookeeper://127.0.0.1:2181 即可使用。

可靠性声明

阿里内部并没有采用 Zookeeper 做为注册中心，而是使用自己实现的基于数据库的注册中心，即：Zookeeper 注册中心并没有在阿里内部长时间运行的可靠性保障，此 Zookeeper 桥接实现只为开源版本提供，其可靠性依赖于 Zookeeper 本身的可靠性。

兼容性声明

因 2.0.8 最初设计的 zookeeper 存储结构不能扩充不同类型的数据，2.0.9 版本做了调整，所以不兼容，需全部改用 2.0.9 版本才行，以后的版本会保持兼容 2.0.9。2.2.0 版本改为基于 zkclient 实现，需增加 zkclient 的依赖包，2.3.0 版本增加了基于 curator 的实现，作为可选实现策略。

建议使用 2.3.3 以上版本的 zookeeper 注册中心客户端 ↩︎

搭建步骤如下：

1、启动 Zookeeper 服务。

$ pwd
/Users/abel/dev/zookeeper-3.4.13

$ bin/zkServer.sh start
bin/zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /Users/abel/dev/zookeeper-3.4.13/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

2、修改 dubbo-demo-provider.xml ，启动 Provider 。

<!--<dubbo:registry address="multicast://224.5.6.7:1234"/>-->
<dubbo:registry address="zookeeper://127.0.0.1:2181"/>

3、修改 dubbo-demo-consumer.xml ，启动 Consumer 。

<!--<dubbo:registry address="multicast://224.5.6.7:1234"/>-->
<dubbo:registry address="zookeeper://127.0.0.1:2181"/>

2.Provider

在 IDEA 中，右键 Debug 运行 com.alibaba.dubbo.demo.provider.Provider 。

当输出如下日志，表示成功：

[18/02/18 10:04:42:042 CST] main  INFO support.ClassPathXmlApplicationContext: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@cd2dae5: startup date [Sun Feb 18 10:04:42 CST 2018]; root of context hierarchy
[18/02/18 10:04:42:042 CST] main  INFO xml.XmlBeanDefinitionReader: Loading XML bean definitions from class path resource [META-INF/spring/dubbo-demo-provider.xml]
[18/02/18 10:04:42:042 CST] main  INFO logger.LoggerFactory: using logger: com.alibaba.dubbo.common.logger.log4j.Log4jLoggerAdapter
[18/02/18 10:04:53:053 CST] main  INFO config.AbstractConfig:  [DUBBO] The service ready on spring started. service: com.alibaba.dubbo.demo.DemoService, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:13:013 CST] main  INFO config.AbstractConfig:  [DUBBO] Export dubbo service com.alibaba.dubbo.demo.DemoService to local registry, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:13:013 CST] main  INFO config.AbstractConfig:  [DUBBO] Export dubbo service com.alibaba.dubbo.demo.DemoService to url dubbo://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&bind.ip=192.168.1.116&bind.port=20880&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43392&qos.port=22222&side=provider&timestamp=1518919503284, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:13:013 CST] main  INFO config.AbstractConfig:  [DUBBO] Register dubbo service com.alibaba.dubbo.demo.DemoService url dubbo://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&bind.ip=192.168.1.116&bind.port=20880&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43392&qos.port=22222&side=provider&timestamp=1518919503284 to registry registry://224.5.6.7:1234/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&pid=43392&qos.port=22222&registry=multicast&timestamp=1518919493265, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:13:013 CST] main  INFO transport.AbstractServer:  [DUBBO] Start NettyServer bind /0.0.0.0:20880, export /192.168.1.116:20880, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:20:020 CST] main  INFO multicast.MulticastRegistry:  [DUBBO] Register: dubbo://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43392&side=provider&timestamp=1518919503284, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:20:020 CST] main  INFO multicast.MulticastRegistry:  [DUBBO] Send broadcast message: register dubbo://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43392&side=provider&timestamp=1518919503284 to /224.5.6.7:1234, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:20:020 CST] DubboMulticastRegistryReceiver  INFO multicast.MulticastRegistry:  [DUBBO] Receive multicast message: register dubbo://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43392&side=provider&timestamp=1518919503284 from /192.168.1.116:1234, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:20:020 CST] main  INFO multicast.MulticastRegistry:  [DUBBO] Subscribe: provider://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&category=configurators&check=false&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43392&side=provider&timestamp=1518919503284, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:20:020 CST] main  INFO multicast.MulticastRegistry:  [DUBBO] Send broadcast message: subscribe provider://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&category=configurators&check=false&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43392&side=provider&timestamp=1518919503284 to /224.5.6.7:1234, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:20:020 CST] DubboMulticastRegistryReceiver  INFO multicast.MulticastRegistry:  [DUBBO] Receive multicast message: subscribe provider://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&category=configurators&check=false&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43392&side=provider&timestamp=1518919503284 from /192.168.1.116:1234, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 10:05:21:021 CST] main  WARN multicast.MulticastRegistry:  [DUBBO] Ignore empty notify urls for subscribe url provider://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&category=configurators&check=false&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43392&side=provider&timestamp=1518919503284, dubbo version: 2.0.0, current host: 192.168.1.116

注意，如果使用 Multicast Registry 作为注册中心，在 IDEA 中需要使用 Debug 模式运行，原因参见：dubbo-demo set “java.net.preferIPv4Stack” not work 。

3. Consumer

在 IDEA 中，右键 Debug 运行 com.alibaba.dubbo.demo.consumer.Consumer 。

当输出如下日志，表示成功：

[18/02/18 09:45:22:022 CST] main  INFO support.ClassPathXmlApplicationContext: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@cd2dae5: startup date [Sun Feb 18 09:45:22 CST 2018]; root of context hierarchy
[18/02/18 09:45:22:022 CST] main  INFO xml.XmlBeanDefinitionReader: Loading XML bean definitions from class path resource [META-INF/spring/dubbo-demo-consumer.xml]
[18/02/18 09:45:22:022 CST] main  INFO logger.LoggerFactory: using logger: com.alibaba.dubbo.common.logger.log4j.Log4jLoggerAdapter
[18/02/18 09:45:45:045 CST] main  INFO multicast.MulticastRegistry:  [DUBBO] Register: consumer://192.168.1.116/com.alibaba.dubbo.demo.DemoService?application=demo-consumer&category=consumers&check=false&dubbo=2.0.0&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43363&qos.port=33333&side=consumer&timestamp=1518918323457, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] main  INFO multicast.MulticastRegistry:  [DUBBO] Send broadcast message: register consumer://192.168.1.116/com.alibaba.dubbo.demo.DemoService?application=demo-consumer&category=consumers&check=false&dubbo=2.0.0&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43363&qos.port=33333&side=consumer&timestamp=1518918323457 to /224.5.6.7:1234, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] main  INFO multicast.MulticastRegistry:  [DUBBO] Subscribe: consumer://192.168.1.116/com.alibaba.dubbo.demo.DemoService?application=demo-consumer&category=providers,configurators,routers&check=false&dubbo=2.0.0&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43363&qos.port=33333&side=consumer&timestamp=1518918323457, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] DubboMulticastRegistryReceiver  INFO multicast.MulticastRegistry:  [DUBBO] Receive multicast message: register consumer://192.168.1.116/com.alibaba.dubbo.demo.DemoService?application=demo-consumer&category=consumers&check=false&dubbo=2.0.0&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43363&qos.port=33333&side=consumer&timestamp=1518918323457 from /192.168.1.116:1234, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] main  INFO multicast.MulticastRegistry:  [DUBBO] Send broadcast message: subscribe consumer://192.168.1.116/com.alibaba.dubbo.demo.DemoService?application=demo-consumer&category=providers,configurators,routers&check=false&dubbo=2.0.0&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43363&qos.port=33333&side=consumer&timestamp=1518918323457 to /224.5.6.7:1234, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] DubboMulticastRegistryReceiver  INFO multicast.MulticastRegistry:  [DUBBO] Receive multicast message: subscribe consumer://192.168.1.116/com.alibaba.dubbo.demo.DemoService?application=demo-consumer&category=providers,configurators,routers&check=false&dubbo=2.0.0&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43363&qos.port=33333&side=consumer&timestamp=1518918323457 from /192.168.1.116:1234, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] DubboMulticastRegistryReceiver  INFO multicast.MulticastRegistry:  [DUBBO] Receive multicast message: register dubbo://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43355&side=provider&timestamp=1518918226970 from /192.168.1.116:1234, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] DubboMulticastRegistryReceiver  INFO multicast.MulticastRegistry:  [DUBBO] Notify urls for subscribe url consumer://192.168.1.116/com.alibaba.dubbo.demo.DemoService?application=demo-consumer&category=providers,configurators,routers&check=false&dubbo=2.0.0&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43363&qos.port=33333&side=consumer&timestamp=1518918323457, urls: [dubbo://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43355&side=provider&timestamp=1518918226970], dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] DubboMulticastRegistryReceiver  INFO transport.AbstractClient:  [DUBBO] Successed connect to server /192.168.1.116:20880 from NettyClient 192.168.1.116 using dubbo version 2.0.0, channel is NettyChannel [channel=[id: 0x1b7bac12, /192.168.1.116:63856 => /192.168.1.116:20880]], dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] DubboMulticastRegistryReceiver  INFO transport.AbstractClient:  [DUBBO] Start NettyClient 123312.local/192.168.1.116 connect to the server /192.168.1.116:20880, dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] main  INFO multicast.MulticastRegistry:  [DUBBO] Notify urls for subscribe url consumer://192.168.1.116/com.alibaba.dubbo.demo.DemoService?application=demo-consumer&category=providers,configurators,routers&check=false&dubbo=2.0.0&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43363&qos.port=33333&side=consumer&timestamp=1518918323457, urls: [dubbo://192.168.1.116:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43355&side=provider&timestamp=1518918226970], dubbo version: 2.0.0, current host: 192.168.1.116
[18/02/18 09:45:45:045 CST] main  INFO config.AbstractConfig:  [DUBBO] Refer dubbo service com.alibaba.dubbo.demo.DemoService from url multicast://224.5.6.7:1234/com.alibaba.dubbo.registry.RegistryService?anyhost=true&application=demo-consumer&check=false&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=43363&qos.port=33333&register.ip=192.168.1.116&remote.timestamp=1518918226970&side=consumer&timestamp=1518918323457, dubbo version: 2.0.0, current host: 192.168.1.116
Hello world, response form provider: 192.168.1.116:20880
Hello world, response form provider: 192.168.1.116:20880
Hello world, response form provider: 192.168.1.116:20880
Hello world, response form provider: 192.168.1.116:20880
Hello world, response form provider: 192.168.1.116:20880
Hello world, response form provider: 192.168.1.116:20880
Hello world, response form provider: 192.168.1.116:20880
Hello world, response form provider: 192.168.1.116:20880
Hello world, response form provider: 192.168.1.116:20880
Hello world, response form provider: 192.168.1.116:20880
Hello world, response form provider: 192.168.1.116:20880