dubbo 分析-调用过程分析

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dubbo 调用过程分析

本章 主要介绍 dubbo 服务和客户端 调用过程。

服务端 接收请求流程

服务端配置

直接采用dubbo 源码例子 dubbo-demo-provider

配置如下：

<!-- provider's application name, used for tracing dependency relationship -->
<dubbo:application name="demo-provider"/>

<!-- use multicast registry center to export service -->
<dubbo:registry address="multicast://224.5.6.7:1234"/>

<!-- use dubbo protocol to export service on port 20880 -->
<dubbo:protocol name="dubbo" port="20880" server="netty4"/>

<!-- service implementation, as same as regular local bean -->
<bean id="demoService" class="com.alibaba.dubbo.demo.provider.DemoServiceImpl"/>

<!-- declare the service interface to be exported -->
<dubbo:service interface="com.alibaba.dubbo.demo.DemoService" ref="demoService" timeout="10000"/>

采用netty4 协议。

服务处理请求流程

说明 ：

其实客户端响应处理流程 和 服务端 请求处理流程差不多。 都是 dubboprotocol 的requestHandler 处理。

nettyServer 和nettyClient 创建会有一个 handler 的warp 过程

public NettyServer(URL url, ChannelHandler handler) throws RemotingException {
    super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));
}  

 protected ChannelHandler wrapInternal(ChannelHandler handler, URL url) {
    return new MultiMessageHandler(new HeartbeatHandler(ExtensionLoader.getExtensionLoader(Dispatcher.class)
            .getAdaptiveExtension().dispatch(handler, url)));
}

Dispatcher 默认扩展 是 AllDispatcher。
public class AllDispatcher implements Dispatcher {

public static final String NAME = "all";

public ChannelHandler dispatch(ChannelHandler handler, URL url) {
    return new AllChannelHandler(handler, url);
}

}

AllChannelHandler 包含了 线程池处理请求.

遇到的错误：

dubbo 源码 example 服务端代码测试 更改为 netty4 协议 ： Unsupported server type: netty4,

Exception in thread “main” com.alibaba.dubbo.rpc.RpcException: Unsupported server type: netty4,

检查发现 dubbo-demo-provider 的pom如下：

<dependencies>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>dubbo-demo-api</artifactId>
            <version>${project.parent.version}</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>dubbo-config-spring</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>dubbo-registry-zookeeper</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>dubbo-registry-multicast</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>dubbo-rpc-dubbo</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>dubbo-remoting-netty</artifactId>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>dubbo-serialization-hessian2</artifactId>
        </dependency>
    </dependencies>

因为是分模块引入 所以默认不存在 netty4 代码：

添加如下 依赖解决问题：

    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>dubbo-remoting-netty4</artifactId>
    </dependency>