Protocol

This article explains how to provide a custom RPC protocol implementation by extending the org.apache.dubbo.rpc.Protocol SPI.

In the Communication Protocol chapter, we learned about several core RPC protocols built into Dubbo: dubbo, rest, and tri, and how to use them. This article explains how to provide a custom RPC protocol implementation by extending the org.apache.dubbo.rpc.Protocol SPI.

There are two ways to create a private protocol: the first is to wrap the existing protocol and add specific business logic. The second is to completely customize a protocol. The former is simpler to implement and is widely used in dubbo, such as ProtocolFilterWrapper, QosProtocolWrapper, and ProtocolListenerWrapper. The latter is relatively complex but offers maximum flexibility; for instance, the built-in protocols dubbo and triple in the Dubbo framework fall under this implementation style.

For the complete source code of this example, refer to dubbo-samples-extensibility. In addition to this example, many Protocol implementations in the core Dubbo repository apache/dubbo and the extension library apache/dubbo-spi-extensions can also serve as extension references:

# Common protocols supported by Dubbo
dubbo=org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol
tri=org.apache.dubbo.rpc.protocol.tri.TripleProtocol

Task Details

Implement a custom protocol edubbo based on the existing dubbo protocol.

Implementation

The edubbo protocol is implemented by wrapping the dubbo protocol.

Code Structure

Common
src
 |-main
    |-java
        |-org
            |-apache
                |-dubbo
                    |-samples
                        |-extensibility
                            |-protocol
                                |-common
                                    |-EnhancedProtocol.java (Implements Protocol interface)
Provider
src
 |-main
    |-java
        |-org
            |-apache
                |-dubbo
                    |-samples
                        |-extensibility
                            |-protocol
                                |-provider
                                    |-ExtensibilityProtocolProviderApplication.java
                                    |-ExtensibilityProtocolServiceImpl.java
    |-resources
        |-META-INF
            |-application.properties (Dubbo Provider configuration file)
            |-dubbo
                |-org.apache.dubbo.rpc.Protocol (Plain text file)
Consumer
src
 |-main
    |-java
        |-org
            |-apache
                |-dubbo
                    |-samples
                        |-extensibility
                            |-protocol
                                |-consumer
                                    |-ExtensibilityProtocolConsumerApplication.java
                                    |-ExtensibilityProtocolConsumerTask.java
    |-resources
        |-META-INF
            |-application.properties (Dubbo Consumer configuration file)
            |-dubbo
                |-org.apache.dubbo.rpc.Protocol (Plain text file)

Code Details

package org.apache.dubbo.samples.extensibility.protocol.common;

import org.apache.dubbo.common.URL;
import org.apache.dubbo.rpc.Protocol;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.Exporter;
import org.apache.dubbo.rpc.ProtocolServer;
import org.apache.dubbo.rpc.RpcException;
import org.apache.dubbo.rpc.model.FrameworkModel;
import org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol;

import java.util.List;

public class EnhancedProtocol implements Protocol {

    public EnhancedProtocol(FrameworkModel frameworkModel) {
        this.protocol = new DubboProtocol(frameworkModel);
    }

    private final Protocol protocol;

    @Override
    public int getDefaultPort() {
        return this.protocol.getDefaultPort();
    }

    @Override
    public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
        // do something
        return this.protocol.export(invoker);
    }

    @Override
    public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
        // do something
        return this.protocol.refer(type, url);
    }

    @Override
    public void destroy() {
        this.protocol.destroy();
    }

    @Override
    public List<ProtocolServer> getServers() {
        return protocol.getServers();
    }
}

SPI Configuration

Provider

Add the following configuration in the resources/META-INF/dubbo/org.apache.dubbo.rpc.Protocol file:

edubbo=org.apache.dubbo.samples.extensibility.protocol.common.EnhancedProtocol
Consumer

Add the following configuration in the resources/META-INF/dubbo/org.apache.dubbo.rpc.Protocol file:

edubbo=org.apache.dubbo.samples.extensibility.protocol.common.EnhancedProtocol

Configuration File

Provider

Add the following configuration in the resources/application.properties file:

# Custom protocol
dubbo.provider.protocol=edubbo
Consumer

Add the following configuration in the resources/application.properties file:

# Custom protocol
dubbo.consumer.protocol=edubbo

Run Results

Run the task using local IDE, the results are as follows:

Registered Protocol

dubbo-samples-extensibility-protocol-output2.jpg

Output Result

dubbo-samples-extensibility-protocol-output1.png

Last modified September 30, 2024: Update & Translate Overview Docs (#3040) (d37ebceaea)