• Elasticsearch：从零开始创建一个 REST handler 插件

    在 Kibana 的 console 中，我们可以使用一些命令对 Elasticsearch 进行交互。那么我们是否可以扩展我们需要的一些命令呢？比如：

    在上面，我们打入 GET _cat/example，它将显示右边的输出。这个是我们扩展的一个命令。

    Elasticsearch 带有一组可以执行各种任务的功能。 但是，如果你想实现自己的任何功能，则需要在 Elasticsearch 的主代码库中实现。 为了保护你免受所有这些额外步骤的影响，Elasticsearch 提供了在 Elasticsearch 代码中添加插件的选项，该插件能够实现你的功能。

    在今天的展示中，我将使用最新的 Elastic Stack 8.4.0 来进行展示。

    安装

    如果你还没有安装好自己的 Elastic Stack，请参考如下的文章来安装 Elasticsearch 及 Kibana：

    创建插件模板

    在我之前的文章 

    我已经展示了如何为 ingest pipeline 创建 processors。在上面的第二篇文章中，我使用了一个叫做 elasticsearch-plugin-archtype 的插件。我们可以使用如下的命令来创建一个最为基本的插件模板：

    1. mvn archetype:generate \
    2.     -DarchetypeGroupId=org.codelibs \
    3.     -DarchetypeArtifactId=elasticsearch-plugin-archetype \
    4.     -DarchetypeVersion=6.6.0 \
    5.     -DgroupId=com.liuxg \
    6.     -DartifactId=elasticsearch-plugin \
    7.     -Dversion=1.0-SNAPSHOT \
    8.     -DpluginName=rest_handler

    上面已经帮我们创建了一个最为基本的插件模板。它在当前的目录下创建了一个叫做 elasticsearch-plugin 的目录。我们首先进入到该目录中：

    1. $ pwd
    2. /Users/liuxg/java/plugins/elasticsearch-plugin
    3. $ tree -L 8
    4. .
    5. ├── pom.xml
    6. └── src
    7.     └── main
    8.         ├── assemblies
    9.         │   └── plugin.xml
    10.         ├── java
    11.         │   └── com
    12.         │       └── liuxg
    13.         │           ├── rest
    14.         │           │   └── Restrest_handlerAction.java
    15.         │           └── rest_handlerPlugin.java
    16.         └── plugin-metadata
    17.             └── plugin-descriptor.properties

    上面是它的文件结构。因为我们想为 Elastic Stack 8.4.0 构建插件，所以，我们必须在 pom.xml 中修改相应的版本信息：

    pom.xml

    1. <?xml version="1.0" encoding="UTF-8"?>
    2. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    3. 	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    4. 	<name>elasticsearch-plugin</name>
    5. 	<modelVersion>4.0.0</modelVersion>
    6. 	<groupId>com.liuxg</groupId>
    7. 	<artifactId>elasticsearch-plugin</artifactId>
    8. 	<version>1.0-SNAPSHOT</version>
    9. 	<packaging>jar</packaging>
    10. 	<description>elasticsearch rest_handler plugin</description>
    11. 	<inceptionYear>2019</inceptionYear>
    12. 	<licenses>
    13. 		<license>
    14. 			<name>The Apache Software License, Version 2.0</name>
    15. 			<url>http://www.apache.org/licenses/LICENSE-2.0.txt</url>
    16. 			<distribution>repo</distribution>
    17. 		</license>
    18. 	</licenses>
    19. 	<properties>
    20. 		<elasticsearch.version>8.4.0</elasticsearch.version>
    21. 		<elasticsearch.plugin.classname>com.liuxg.rest_handlerPlugin</elasticsearch.plugin.classname>
    22. 		<log4j.version>2.11.1</log4j.version>
    23. 		<maven.compiler.source>1.8</maven.compiler.source>
    24. 		<maven.compiler.target>1.8</maven.compiler.target>
    25. 	</properties>
    26. 	<build>
    27. 		<plugins>
    28. 			<plugin>
    29. 				<artifactId>maven-compiler-plugin</artifactId>
    30. 				<version>3.8.0</version>
    31. 				<configuration>
    32. 					<source>${maven.compiler.source}</source>
    33. 					<target>${maven.compiler.target}</target>
    34. 					<encoding>UTF-8</encoding>
    35. 				</configuration>
    36. 			</plugin>
    37. 			<plugin>
    38. 				<artifactId>maven-surefire-plugin</artifactId>
    39. 				<version>2.22.1</version>
    40. 				<configuration>
    41. 					<includes>
    42. 						<include>**/*Tests.java</include>
    43. 					</includes>
    44. 				</configuration>
    45. 			</plugin>
    46. 			<plugin>
    47. 				<artifactId>maven-source-plugin</artifactId>
    48. 				<version>3.0.1</version>
    49. 				<executions>
    50. 					<execution>
    51. 						<id>attach-sources</id>
    52. 						<goals>
    53. 							<goal>jar</goal>
    54. 						</goals>
    55. 					</execution>
    56. 				</executions>
    57. 			</plugin>
    58. 			<plugin>
    59. 				<artifactId>maven-assembly-plugin</artifactId>
    60. 				<version>3.1.0</version>
    61. 				<configuration>
    62. 					<appendAssemblyId>false</appendAssemblyId>
    63. 					<outputDirectory>${project.build.directory}/releases/</outputDirectory>
    64. 					<descriptors>
    65. 						<descriptor>${basedir}/src/main/assemblies/plugin.xml</descriptor>
    66. 					</descriptors>
    67. 				</configuration>
    68. 				<executions>
    69. 					<execution>
    70. 						<phase>package</phase>
    71. 						<goals>
    72. 							<goal>single</goal>
    73. 						</goals>
    74. 					</execution>
    75. 				</executions>
    76. 			</plugin>
    77. 		</plugins>
    78. 	</build>
    79. 	<dependencies>
    80. 		<dependency>
    81. 			<groupId>org.elasticsearch</groupId>
    82. 			<artifactId>elasticsearch</artifactId>
    83. 			<version>${elasticsearch.version}</version>
    84. 			<scope>provided</scope>
    85. 		</dependency>
    86. 		<dependency>
    87. 			<groupId>org.apache.logging.log4j</groupId>
    88. 			<artifactId>log4j-api</artifactId>
    89. 			<version>${log4j.version}</version>
    90. 			<scope>provided</scope>
    91. 		</dependency>
    92. 	</dependencies>
    93. </project>

    在上面，我们把 elasticsearch.version 设置为 8.4.0。其它的保持不变。

    接下来，我们来修改 rest_handlerPlugin.java 文件：

    rest_handlerPlugin.java

    1. package com.liuxg;
    2.  
    3. import java.util.List;
    4. import java.util.function.Supplier;
    5.  
    6. import com.liuxg.rest.Restrest_handlerAction;
    7. import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
    8. import org.elasticsearch.cluster.node.DiscoveryNodes;
    9. import org.elasticsearch.common.settings.ClusterSettings;
    10. import org.elasticsearch.common.settings.IndexScopedSettings;
    11. import org.elasticsearch.common.settings.Settings;
    12. import org.elasticsearch.common.settings.SettingsFilter;
    13. import org.elasticsearch.plugins.ActionPlugin;
    14. import org.elasticsearch.plugins.Plugin;
    15. import org.elasticsearch.rest.RestController;
    16. import org.elasticsearch.rest.RestHandler;
    17.  
    18. import static java.util.Collections.singletonList;
    19.  
    20. public class rest_handlerPlugin extends Plugin implements ActionPlugin {
    21.     @Override
    22.     public List<RestHandler> getRestHandlers(final Settings settings,
    23.                                              final RestController restController,
    24.                                              final ClusterSettings clusterSettings,
    25.                                              final IndexScopedSettings indexScopedSettings,
    26.                                              final SettingsFilter settingsFilter,
    27.                                              final IndexNameExpressionResolver indexNameExpressionResolver,
    28.                                              final Supplier<DiscoveryNodes> nodesInCluster) {
    29.         return singletonList(new Restrest_handlerAction());
    30.     }
    31. }

    这个文件会让 Elasticsearch 知道你的插件。

    我们接下来修改 Restrest_handlerAction.java 文件如下：

    Restrest_handlerAction.java

    1. package com.liuxg.rest;
    2.  
    3. import org.elasticsearch.client.internal.node.NodeClient;
    4. import org.elasticsearch.common.Table;
    5. import org.elasticsearch.rest.RestRequest;
    6. import org.elasticsearch.rest.RestResponse;
    7. import org.elasticsearch.rest.action.cat.AbstractCatAction;
    8. import org.elasticsearch.rest.action.cat.RestTable;
    9.  
    10. import java.util.List;
    11.  
    12. import static org.elasticsearch.rest.RestRequest.Method.GET;
    13. import static org.elasticsearch.rest.RestRequest.Method.POST;
    14.  
    15.  
    16. public class Restrest_handlerAction extends AbstractCatAction {
    17.     @Override
    18.     public List routes() {
    19.         return List.of(
    20.                 new Route(GET, "/_cat/example"),
    21.                 new Route(POST, "/_cat/example"));
    22.     }
    23.  
    24.     @Override
    25.     public String getName() {
    26.         return "rest_handler_cat_example";
    27.     }
    28.  
    29.     @Override
    30.     protected RestChannelConsumer doCatRequest(final RestRequest request, final NodeClient client) {
    31.         final String message = request.param("message", "Hello from Cat Example action");
    32.  
    33.         Table table = getTableWithHeader(request);
    34.         table.startRow();
    35.         table.addCell(message);
    36.         table.endRow();
    37.         return channel -> {
    38.             try {
    39.                 channel.sendResponse(RestTable.buildResponse(table, channel));
    40.             } catch (final Exception e) {
    41.                 channel.sendResponse(new RestResponse(channel, e));
    42.             }
    43.         };
    44.     }
    45.  
    46.     @Override
    47.     protected void documentation(StringBuilder sb) {
    48.         sb.append(documentation());
    49.     }
    50.  
    51.     public static String documentation() {
    52.         return "/_cat/example\n";
    53.     }
    54.  
    55.     @Override
    56.     protected Table getTableWithHeader(RestRequest request) {
    57.         final Table table = new Table();
    58.         table.startHeaders();
    59.         table.addCell("test", "desc:test");
    60.         table.endHeaders();
    61.         return table;
    62.     }
    63. }

    该文件将定义插件的路由和处理这些路由的代码。

    这样我们就修改完了我们的代码。

    编译

    我们在项目的根目录下使人如下的命令来进行编译：

    mvn clean install
    1. $ mvn clean install
    2. [INFO] Scanning for projects...
    3. [INFO] 
    4. [INFO] -------------------< com.liuxg:elasticsearch-plugin >-------------------
    5. [INFO] Building elasticsearch-plugin 1.0-SNAPSHOT
    6. [INFO] --------------------------------[ jar ]---------------------------------
    7. [INFO] 
    8. [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ elasticsearch-plugin ---
    9. [INFO] 
    10. [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ elasticsearch-plugin ---
    11. [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
    12. [INFO] skip non existing resourceDirectory /Users/liuxg/java/plugins/elasticsearch-plugin/src/main/resources
    13. [INFO] 
    14. [INFO] --- maven-compiler-plugin:3.8.0:compile (default-compile) @ elasticsearch-plugin ---
    15. [INFO] Changes detected - recompiling the module!
    16. [INFO] Compiling 2 source files to /Users/liuxg/java/plugins/elasticsearch-plugin/target/classes
    17. [INFO] 
    18. [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ elasticsearch-plugin ---
    19. [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
    20. [INFO] skip non existing resourceDirectory /Users/liuxg/java/plugins/elasticsearch-plugin/src/test/resources
    21. [INFO] 
    22. [INFO] --- maven-compiler-plugin:3.8.0:testCompile (default-testCompile) @ elasticsearch-plugin ---
    23. [INFO] No sources to compile
    24. [INFO] 
    25. [INFO] --- maven-surefire-plugin:2.22.1:test (default-test) @ elasticsearch-plugin ---
    26. [INFO] No tests to run.
    27. [INFO] 
    28. [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ elasticsearch-plugin ---
    29. [INFO] Building jar: /Users/liuxg/java/plugins/elasticsearch-plugin/target/elasticsearch-plugin-1.0-SNAPSHOT.jar
    30. [INFO] 
    31. [INFO] >>> maven-source-plugin:3.0.1:jar (attach-sources) > generate-sources @ elasticsearch-plugin >>>
    32. [INFO] 
    33. [INFO] <<< maven-source-plugin:3.0.1:jar (attach-sources) < generate-sources @ elasticsearch-plugin <<<
    34. [INFO] 
    35. [INFO] 
    36. [INFO] --- maven-source-plugin:3.0.1:jar (attach-sources) @ elasticsearch-plugin ---
    37. [INFO] Building jar: /Users/liuxg/java/plugins/elasticsearch-plugin/target/elasticsearch-plugin-1.0-SNAPSHOT-sources.jar
    38. [INFO] 
    39. [INFO] --- maven-assembly-plugin:3.1.0:single (default) @ elasticsearch-plugin ---
    40. [INFO] Reading assembly descriptor: /Users/liuxg/java/plugins/elasticsearch-plugin/src/main/assemblies/plugin.xml
    41. [WARNING] The following patterns were never triggered in this artifact exclusion filter:
    42. o  'org.elasticsearch:elasticsearch'
    43.  
    44. [INFO] Building zip: /Users/liuxg/java/plugins/elasticsearch-plugin/target/releases/elasticsearch-plugin-1.0-SNAPSHOT.zip
    45. [INFO] 
    46. [INFO] --- maven-install-plugin:2.4:install (default-install) @ elasticsearch-plugin ---
    47. [INFO] Installing /Users/liuxg/java/plugins/elasticsearch-plugin/target/elasticsearch-plugin-1.0-SNAPSHOT.jar to /Users/liuxg/.m2/repository/com/liuxg/elasticsearch-plugin/1.0-SNAPSHOT/elasticsearch-plugin-1.0-SNAPSHOT.jar
    48. [INFO] Installing /Users/liuxg/java/plugins/elasticsearch-plugin/pom.xml to /Users/liuxg/.m2/repository/com/liuxg/elasticsearch-plugin/1.0-SNAPSHOT/elasticsearch-plugin-1.0-SNAPSHOT.pom
    49. [INFO] Installing /Users/liuxg/java/plugins/elasticsearch-plugin/target/elasticsearch-plugin-1.0-SNAPSHOT-sources.jar to /Users/liuxg/.m2/repository/com/liuxg/elasticsearch-plugin/1.0-SNAPSHOT/elasticsearch-plugin-1.0-SNAPSHOT-sources.jar
    50. [INFO] Installing /Users/liuxg/java/plugins/elasticsearch-plugin/target/releases/elasticsearch-plugin-1.0-SNAPSHOT.zip to /Users/liuxg/.m2/repository/com/liuxg/elasticsearch-plugin/1.0-SNAPSHOT/elasticsearch-plugin-1.0-SNAPSHOT.zip
    51. [INFO] ------------------------------------------------------------------------
    52. [INFO] BUILD SUCCESS
    53. [INFO] ------------------------------------------------------------------------
    54. [INFO] Total time:  5.352 s
    55. [INFO] Finished at: 2022-09-06T10:55:38+08:00
    56. [INFO] ------------------------------------------------------------------------

    编译成功后，我们可以在 target 目录先看到如下的安装文件：

    1. $ pwd
    2. /Users/liuxg/java/plugins/elasticsearch-plugin
    3. $ ls target/releases
    4. elasticsearch-plugin-1.0-SNAPSHOT.zip

    上面显示的 elasticsearch-plugin-1.0-SNAPSHOT.zip 就是我们可以安装的插件文件。

    安装插件并测试插件

    我们接下来换到 Elasticsearch 的安装目录下，并打入如下的命令：

    1. $ pwd
    2. /Users/liuxg/elastic0/elasticsearch-8.4.0
    3. $ bin/elasticsearch-plugin install file:Users/liuxg/java/plugins/elasticsearch-plugin/target/releases/elasticsearch-plugin-1.0-SNAPSHOT.zip
    4. -> Installing file:Users/liuxg/java/plugins/elasticsearch-plugin/target/releases/elasticsearch-plugin-1.0-SNAPSHOT.zip
    5. -> Downloading file:Users/liuxg/java/plugins/elasticsearch-plugin/target/releases/elasticsearch-plugin-1.0-SNAPSHOT.zip
    6. [=================================================] 100%   
    7. -> Installed rest_handler
    8. -> Please restart Elasticsearch to activate any plugins installed
    9. $ ./bin/elasticsearch-plugin list
    10. rest_handler

    从上面的显示中，我们可以看出来 rest_handler 插件已经被成功地安装。我们接下来需要重新启动 Elasticsearch。这个非常重要！

    我们打开 Kibana，并打入如下的命令：

    我们也可以直接在 terminal 中打入如下的命令：

    curl -k --user elastic:V_USqc1cWM40W_pIHnni https://localhost:9200/_cat/example
    1. $ curl -k --user elastic:V_USqc1cWM40W_pIHnni https://localhost:9200/_cat/example
    2. Hello from Cat Example action

     整个项目的代码可以在地址下载：GitHub - liu-xiao-guo/rest_handler_plugin

    参考：

    【1】elasticsearch/plugins/examples at main · elastic/elasticsearch · GitHub

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  • 原文地址：https://blog.csdn.net/UbuntuTouch/article/details/126717927