1、backgroupd

• ElasticSearch有提供丰富的plugin接口，我们自己能实现plugin来自定义需求。

• 我们的ElasticSearch是用来做时序性分析数据库，所以就会存在数据的高低峰分别。我们想要控制ElasticSearch的rebalance触发机制，避免在高峰期触发rebalance导致磁盘与网络负载大影响到正常的业务

2、how to write the plugin

（1）项目架构

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（2）file

plugin.xml
这个文件不需要修改，可以直接使用

<?xml version="1.0"?>
<assembly>
    <id>plugin</id>
    <formats>
        <format>zip</format>
    </formats>
    <includeBaseDirectory>false</includeBaseDirectory>
    <files>
        <file>
            <source>${project.basedir}/src/main/resources/plugin-descriptor.properties</source>
            <outputDirectory/>
            <filtered>true</filtered>
        </file>
    </files>
    <dependencySets>
        <dependencySet>
            <outputDirectory/>
            <useProjectArtifact>true</useProjectArtifact>
            <useTransitiveFiltering>true</useTransitiveFiltering>
        </dependencySet>
    </dependencySets>
</assembly>

plugin-descriptor.properties
这个文件需要修改classname对应的类名全路径，即自己实现的那个plugin类。

description=test
version=1.0.0
name=time-decider
classname=com.cnc.baiyx.plugin.rebalance.MyDecidersPlugin
java.version=${java.version}
elasticsearch.version=${elasticsearch.version}

pom.xml
这个文件需要按照各自的使用情况修改java.version与elasticsearch.version

<?xml version="1.0" encoding="UTF-8"?>
<project
    xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>org.example</groupId>
    <artifactId>elasticsearch-plugin</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <elasticsearch.version>7.8.0</elasticsearch.version>
        <java.version>13</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
            <version>${elasticsearch.version}</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>2.7</version>
            <scope>provided</scope>
        </dependency>
        <!-- Testing -->
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.7</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch.test</groupId>
            <artifactId>framework</artifactId>
            <version>${elasticsearch.version}</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>3.1.1</version>
                <configuration>
                    <appendAssemblyId>false</appendAssemblyId>
                    <outputDirectory>target</outputDirectory>
                    <descriptors>
                        <descriptor>src/main/assembly/plugin.xml</descriptor>
                    </descriptors>
                </configuration>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.7.0</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.20.1</version>
                <configuration>
                    <skipTests>true</skipTests>
                </configuration>
            </plugin>
        </plugins>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <filtering>false</filtering>
                <excludes>
                    <exclude>plugin-descriptor.properties</exclude>
                </excludes>
            </resource>
        </resources>
    </build>
</project>

到这步项目的框架就搭建好了。可以根据各自的需求实现自己想要的功能了。

3、部署

1. maven 打包，把zip包上传到服务器上
2. 到es的bin目录下执行./elasticsearch-plugin install file://[filename],filename替换成zip包全路径
3. 重启服务
4. 其他：elasticsearch-plugin list可以看到所有plugin；elasticsearch-plugin remove [plugin-name]卸载plugin

4、test

1、先关闭rebalance
2、手动触发rereoute，使分片分布不均衡。

image.png

3、开启rebalance，集群自动触发rebalance。由于在时间控制范围内，rebalance成功

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