Custom Extensions on Apache Dubbo

Basic Steps to Customize SPI Extensions

Mon, 01 Jan 0001 00:00:00 +0000

Taking the RPC Protocol Plugin as an example, this section demonstrates how to use the SPI plugin provided by Dubbo to provide a custom RPC protocol implementation. If you want to understand how the SPI mechanism works and the list of built-in SPI extension points in the framework, please refer to the Reference Manual - SPI Extension.

1. Provide SPI Plugin Implementation Class

Provide a Java class that implements the org.apache.dubbo.rpc.Protocol interface.

Filter

Mon, 01 Jan 0001 00:00:00 +0000

In the section RPC Framework - Filter Request Interception, we learned about the working mechanism of Filters and some built-in Filter implementations provided by the Dubbo framework. In this article, we will learn how to extend custom filter implementations: a unified Filter processor that can handle and validate returned results, reducing disruptions to developers.

The complete source code for this example can be found at dubbo-samples-extensibility. In addition to this example, many Filter implementations in the Dubbo core repository apache/dubbo and the extension library apache/dubbo-spi-extensions can serve as reference implementations.

Protocol

Mon, 01 Jan 0001 00:00:00 +0000

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.

Registry

Mon, 01 Jan 0001 00:00:00 +0000

In the Service Discovery chapter, we learned about the usage and working principles of several core built-in registry implementations in Dubbo, such as Nacos and Zookeeper. This article explains how to provide a custom registry implementation by extending the org.apache.dubbo.registry.client.ServiceDiscovery and org.apache.dubbo.registry.nacos.NacosServiceDiscoveryFactory SPI.

For the complete source code of this example, please refer to dubbo-registry-etcd. In addition to this example, many registry extension implementations in the core repository apache/dubbo and the extension library apache/dubbo-spi-extensions can serve as references for extensions:

Router

Mon, 01 Jan 0001 00:00:00 +0000

By customizing the router, specific routing methods can be implemented based on the characteristics of business scenarios. Please refer to the source code for the router extension implementation in the example at dubbo-samples-extensibility .

Before You Begin

Task Details

Use the first provided service Provider for all requests. If this Provider goes offline, choose a new Provider.

Implementation Method

In the Consumer, customize a Router that saves the Provider used in the first call. If there are subsequent requests and the Provider list includes the Provider used in the first call, continue to use that Provider; otherwise, select a new Provider.