Version 1.0 of the documentation is no longer actively maintained. The site that you are currently viewing is an archived snapshot. For up-to-date documentation, see the latest version.

HugeGraph Plugin机制及插件扩展流程

背景

HugeGraph不仅开源开放，而且要做到简单易用，一般用户无需更改源码也能轻松增加插件扩展功能。
HugeGraph支持多种内置存储后端，也允许用户无需更改现有源码的情况下扩展自定义后端。
HugeGraph支持全文检索，全文检索功能涉及到各语言分词，目前已内置8种中文分词器，也允许用户无需更改现有源码的情况下扩展自定义分词器。

可扩展维度

目前插件方式提供如下几个维度的扩展项：

后端存储
序列化器
自定义配置项
分词器

插件实现机制

HugeGraph提供插件接口HugeGraphPlugin，通过Java SPI机制支持插件化
HugeGraph提供了4个扩展项注册函数：registerOptions()、registerBackend()、registerSerializer()、registerAnalyzer()
插件实现者实现相应的Options、Backend、Serializer或Analyzer的接口
插件实现者实现HugeGraphPlugin接口的register()方法，在该方法中注册上述第3点所列的具体实现类，并打成jar包
插件使用者将jar包放在HugeGraph Server安装目录的plugins目录下，修改相关配置项为插件自定义值，重启即可生效

插件实现流程实例

1 新建一个maven项目

1.1 项目名称取名：hugegraph-plugin-demo

1.2 添加`hugegraph-core` Jar包依赖

maven pom.xml详细内容如下：

 1<?xml version="1.0" encoding="UTF-8"?>
 2
 3<project xmlns="http://maven.apache.org/POM/4.0.0"
 4         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 5         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 6
 7    <modelVersion>4.0.0</modelVersion>
 8    <groupId>com.baidu.hugegraph</groupId>
 9    <artifactId>hugegraph-plugin-demo</artifactId>
10    <version>1.0.0</version>
11    <packaging>jar</packaging>
12
13    <name>hugegraph-plugin-demo</name>
14
15    <dependencies>
16        <dependency>
17            <groupId>com.baidu.hugegraph</groupId>
18            <artifactId>hugegraph-core</artifactId>
19            <version>${project.version}</version>
20        </dependency>
21    </dependencies>
22</project>

2 实现扩展功能

2.1 扩展自定义后端

2.1.1 实现接口BackendStoreProvider

可实现接口：com.baidu.hugegraph.backend.store.BackendStoreProvider
或者继承抽象类：com.baidu.hugegraph.backend.store.AbstractBackendStoreProvider

以RocksDB后端RocksDBStoreProvider为例：

 1public class RocksDBStoreProvider extends AbstractBackendStoreProvider {
 2
 3    protected String database() {
 4        return this.graph().toLowerCase();
 5    }
 6
 7    @Override
 8    protected BackendStore newSchemaStore(String store) {
 9        return new RocksDBSchemaStore(this, this.database(), store);
10    }
11
12    @Override
13    protected BackendStore newGraphStore(String store) {
14        return new RocksDBGraphStore(this, this.database(), store);
15    }
16
17    @Override
18    public String type() {
19        return "rocksdb";
20    }
21
22    @Override
23    public String version() {
24        return "1.0";
25    }
26}

2.1.2 实现接口BackendStore

BackendStore接口定义如下：

 1public interface BackendStore {
 2    // Store name
 3    public String store();
 4
 5    // Database name
 6    public String database();
 7
 8    // Get the parent provider
 9    public BackendStoreProvider provider();
10
11    // Open/close database
12    public void open(HugeConfig config);
13    public void close();
14
15    // Initialize/clear database
16    public void init();
17    public void clear();
18
19    // Add/delete data
20    public void mutate(BackendMutation mutation);
21
22    // Query data
23    public Iterator<BackendEntry> query(Query query);
24
25    // Transaction
26    public void beginTx();
27    public void commitTx();
28    public void rollbackTx();
29
30    // Get metadata by key
31    public <R> R metadata(HugeType type, String meta, Object[] args);
32
33    // Backend features
34    public BackendFeatures features();
35
36    // Generate an id for a specific type
37    public Id nextId(HugeType type);
38}

2.1.3 扩展自定义序列化器

序列化器必须继承抽象类：com.baidu.hugegraph.backend.serializer.AbstractSerializer(implements GraphSerializer, SchemaSerializer) 主要接口的定义如下：

 1public interface GraphSerializer {
 2    public BackendEntry writeVertex(HugeVertex vertex);
 3    public BackendEntry writeVertexProperty(HugeVertexProperty<?> prop);
 4    public HugeVertex readVertex(HugeGraph graph, BackendEntry entry);
 5    public BackendEntry writeEdge(HugeEdge edge);
 6    public BackendEntry writeEdgeProperty(HugeEdgeProperty<?> prop);
 7    public HugeEdge readEdge(HugeGraph graph, BackendEntry entry);
 8    public BackendEntry writeIndex(HugeIndex index);
 9    public HugeIndex readIndex(HugeGraph graph, ConditionQuery query, BackendEntry entry);
10    public BackendEntry writeId(HugeType type, Id id);
11    public Query writeQuery(Query query);
12}
13
14public interface SchemaSerializer {
15    public BackendEntry writeVertexLabel(VertexLabel vertexLabel);
16    public VertexLabel readVertexLabel(HugeGraph graph, BackendEntry entry);
17    public BackendEntry writeEdgeLabel(EdgeLabel edgeLabel);
18    public EdgeLabel readEdgeLabel(HugeGraph graph, BackendEntry entry);
19    public BackendEntry writePropertyKey(PropertyKey propertyKey);
20    public PropertyKey readPropertyKey(HugeGraph graph, BackendEntry entry);
21    public BackendEntry writeIndexLabel(IndexLabel indexLabel);
22    public IndexLabel readIndexLabel(HugeGraph graph, BackendEntry entry);
23}

2.1.4 扩展自定义配置项

增加自定义后端时，可能需要增加新的配置项，实现流程主要包括：

增加配置项容器类，并实现接口com.baidu.hugegraph.config.OptionHolder
提供单例方法public static OptionHolder instance()，并在对象初始化时调用方法OptionHolder.registerOptions()
增加配置项声明，单值配置项类型为ConfigOption、多值配置项类型为ConfigListOption

以RocksDB配置项定义为例：

 1public class RocksDBOptions extends OptionHolder {
 2
 3    private RocksDBOptions() {
 4        super();
 5    }
 6
 7    private static volatile RocksDBOptions instance;
 8
 9    public static synchronized RocksDBOptions instance() {
10        if (instance == null) {
11            instance = new RocksDBOptions();
12            instance.registerOptions();
13        }
14        return instance;
15    }
16
17    public static final ConfigOption<String> DATA_PATH =
18            new ConfigOption<>(
19                    "rocksdb.data_path",
20                    "The path for storing data of RocksDB.",
21                    disallowEmpty(),
22                    "rocksdb-data"
23            );
24
25    public static final ConfigOption<String> WAL_PATH =
26            new ConfigOption<>(
27                    "rocksdb.wal_path",
28                    "The path for storing WAL of RocksDB.",
29                    disallowEmpty(),
30                    "rocksdb-data"
31            );
32
33    public static final ConfigListOption<String> DATA_DISKS =
34            new ConfigListOption<>(
35                    "rocksdb.data_disks",
36                    false,
37                    "The optimized disks for storing data of RocksDB. " +
38                    "The format of each element: `STORE/TABLE: /path/to/disk`." +
39                    "Allowed keys are [graph/vertex, graph/edge_out, graph/edge_in, " +
40                    "graph/secondary_index, graph/range_index]",
41                    null,
42                    String.class,
43                    ImmutableList.of()
44            );
45}

2.2 扩展自定义分词器

分词器需要实现接口com.baidu.hugegraph.analyzer.Analyzer，以实现一个SpaceAnalyzer空格分词器为例。

 1package com.baidu.hugegraph.plugin;
 2
 3import java.util.Arrays;
 4import java.util.HashSet;
 5import java.util.Set;
 6
 7import com.baidu.hugegraph.analyzer.Analyzer;
 8
 9public class SpaceAnalyzer implements Analyzer {
10
11    @Override
12    public Set<String> segment(String text) {
13        return new HashSet<>(Arrays.asList(text.split(" ")));
14    }
15}

3. 实现插件接口，并进行注册

插件注册入口为HugeGraphPlugin.register()，自定义插件必须实现该接口方法，在其内部注册上述定义好的扩展项。接口com.baidu.hugegraph.plugin.HugeGraphPlugin定义如下：

 1public interface HugeGraphPlugin {
 2
 3    public String name();
 4
 5    public void register();
 6
 7    public String supportsMinVersion();
 8
 9    public String supportsMaxVersion();
10}

并且HugeGraphPlugin提供了4个静态方法用于注册扩展项：

registerOptions(String name, String classPath)：注册配置项
registerBackend(String name, String classPath)：注册后端（BackendStoreProvider）
registerSerializer(String name, String classPath)：注册序列化器
registerAnalyzer(String name, String classPath)：注册分词器

下面以注册SpaceAnalyzer分词器为例：

 1package com.baidu.hugegraph.plugin;
 2
 3public class DemoPlugin implements HugeGraphPlugin {
 4
 5    @Override
 6    public String name() {
 7        return "demo";
 8    }
 9
10    @Override
11    public void register() {
12        HugeGraphPlugin.registerAnalyzer("demo", SpaceAnalyzer.class.getName());
13    }
14}

4. 配置SPI入口

确保services目录存在：hugegraph-plugin-demo/resources/META-INF/services
在services目录下建立文本文件：com.baidu.hugegraph.plugin.HugeGraphPlugin
文件内容如下：com.baidu.hugegraph.plugin.DemoPlugin

5. 打Jar包

通过maven打包，在项目目录下执行命令mvn package，在target目录下会生成Jar包文件。使用时将该Jar包拷到plugins目录，重启服务即可生效。

HugeGraph Plugin机制及插件扩展流程

背景

可扩展维度

插件实现机制

插件实现流程实例

1 新建一个maven项目

1.1 项目名称取名：hugegraph-plugin-demo

1.2 添加hugegraph-core Jar包依赖

2 实现扩展功能

2.1 扩展自定义后端

2.1.1 实现接口BackendStoreProvider

2.1.2 实现接口BackendStore

2.1.3 扩展自定义序列化器

2.1.4 扩展自定义配置项

2.2 扩展自定义分词器

3. 实现插件接口，并进行注册

4. 配置SPI入口

5. 打Jar包

Ask AI

1.2 添加`hugegraph-core` Jar包依赖