Config Change Plugin

Translated by AI.

Community has long been hoping for Nacos Configuration Center to provide notifications to specific systems when configurations change. These notifications are used for recording, warning, and auditing purposes. Before version 2.3.0, the only way to achieve this was by simulating Nacos client subscription to the configurations. This approach involved subscribing to changes in core configurations and executing functionalities such as sending records and warnings upon receiving change notifications.

However, this implementation had a few significant issues. Firstly, individual configurations needed to be added one by one, making it difficult to capture all configuration changes. Secondly, functionalities could only be executed after configuration changes, and there was no capability for performing pre-change operations such as format validation or whitelist validation.

To address these limitations, starting from Nacos version 2.3.0, Nacos introduced support for injecting configuration change plugins through the SPI. This allows users to define custom plugins to execute specific logic before and after configuration changes. Examples of such logic include format validation, whitelist validation, and webhook integrations.

These enhancements provide more flexibility and control for users to implement their own custom logic before and after configuration changes in Nacos Configuration Center.

Concepts in Config Change Plugin

Nacos’s configuration change plugin design takes inspiration from the aspect-oriented programming (AOP) paradigm. It treats configuration change operations, such as adding, updating, and deleting, as the pointcuts and weaves the plugins before and after these pointcuts.

ConfigChangePointCutTypes

Nacos has categorized the configuration change operations based on their behaviors and sources. These configuration change operations are defined as several ConfigChangePointCutTypes in com.alibaba.nacos.plugin.config.constants.ConfigChangePointCutTypes. The specific details are as follows:

ConfigChangeExecuteTypes

In Nacos, the configuration change plugins need to be executed before or after the ConfigChangePointCutTypes by selecting the ConfigChangeExecuteTypes. These execution types are defined in com.alibaba.nacos.plugin.config.constants.ConfigChangeExecuteTypes. The specific details are as follows:

Plugin Development

To develop a config change plugin for the Nacos server, you first need to depend on the relevant API of the config change plugin.

        <dependency>
            <groupId>com.alibaba.nacos</groupId>
            <artifactId>nacos-config-plugin</artifactId>
            <version>${project.version}</version>
        </dependency>

${project.version} is the Nacos version, at least 2.3.0.

Then implement com.alibaba.nacos.plugin.config.spi.ConfigChangePluginService interface, which include following method:

ConfigChangeRequest and ConfigChangeResponse refer to the contents passed in during the execution of logic and the resulting execution outcome, respectively.

ConfigChangeRequest mainly include follow contents:

ConfigChangeResponse mainly include follow contents:

Load Plugin

After the plugin finished, it needs to be packaged into jar/zip and places in the classpath of the nacos server. If you don’t know how to add plugins into the classpath, please place plugins under ${nacos-server.path}/plugins directly.

After Adding plugins into classpath, also need to modify some configuration in ${nacos-server.path}/conf/application.properties.

### The name of the config change plugin enabled in Nacos, corresponding to the return value of com.alibaba.nacos.plugin.config.spi.ConfigChangePluginService's getServiceType method.
nacos.core.config.plugin.${configChangePluginName}.enabled=true

After restarting the Nacos cluster and completing the startup, you can see the following logs in ${nacos-server.path}/logs/plugin-control.log:

[ConfigChangePluginManager] Load ${className}(${classFullName}) ConfigChangeServiceName(${configChangePluginName}) successfully.

Custom Plugin properties

Some plugins may want to set certain parameters through a configuration file. Custom plugins can modify the following configurations in ${nacos-server.path}/conf/application.properties to achieve this:

### The name of the config change plugin enabled in Nacos, corresponding to the return value of com.alibaba.nacos.plugin.config.spi.ConfigChangePluginService's getServiceType method.
nacos.core.config.plugin.${configChangePluginName}.${propertyKey}=${propertyValue}

In ConfigChangeRequest, getting properties by following way:

final Properties properties = (Properties) configChangeRequest.getArg(ConfigChangeConstants.PLUGIN_PROPERTIES);
final String ${propertyKey} = properties.getProperty("${propertyKey}");

Plugin Demo

In the nacos-group/nacos-plugin repository, there is a demo implementation of a configuration change plugin. This demo plugin implements validation of the configuration content format, validation of the whitelist for importing configuration names, and a webhook callback after the change. To use this plugin, you need to package it as a JAR/ZIP file and place it in the classpath of the Nacos server. Additionally, add the following configuration in ${nacos-server.path}/conf/application.properties:

# webhook
#nacos.core.config.plugin.webhook.enabled=true
# It is recommended to use EB https://help.aliyun.com/document_detail/413974.html
#nacos.core.config.plugin.webhook.url=http://${webhookIp}:${webhookPort}/${webhookUri}?token=***
# The content push max capacity ,byte
#nacos.core.config.plugin.webhook.contentMaxCapacity=102400

# whitelist
#nacos.core.config.plugin.whitelist.enabled=true
# The import file suffixs
#nacos.core.config.plugin.whitelist.suffixs=xml,text,properties,yaml,html

# fileformatcheck,which validate the import file of type and content
#nacos.core.config.plugin.fileformatcheck.enabled=true