• GreatSQL社区原创内容未经授权不得随意使用，转载请联系小编并注明来源。
• GreatSQL是MySQL的国产分支版本，使用上与MySQL一致。

  一、Debezium介绍

  摘自官网:

  Debezium is a set of distributed services to capture changes in your databases so that your applications can see those changes and respond to them. Debezium records all row-level changes within each database table in a change event stream, and applications simply read these streams to see the change events in the same order in which they occurred.

简单理解就是Debezium可以捕获数据库中所有行级的数据变化并包装成事件流顺序输出。

二、基本使用

下面以MySQL为例介绍Debezium的基本使用。

1. MySQL的准备工作

1. 准备一个MySQL用户并且拥有相应权限，像这样：

   CREATE USER 'dbz'@'%' IDENTIFIED BY 'dbzpwd';
   

GRANT SELECT, RELOAD, SHOW DATABASES, REPLICATION SLAVE, REPLICATION CLIENT ON . TO 'dbz' IDENTIFIED BY 'dbzpwd';

2. 检查MySQL是否开启`log-bin`
```sql
SELECT variable_value as "BINARY LOGGING STATUS (log-bin) ::" FROM information_schema.global_variables WHERE variable_name='log_bin';

-- If the following error occurs: The 'INFORMATION_SCHEMA.GLOBAL_VARIABLES' feature is disabled...
-- please execute the given SQL again after execute this SQL: set global show_compatibility_56=on;

如果是OFF则需要修改MySQL配置文件，类似下面这样：

server-id         = 223344        #必须有
log_bin           = mysql-bin    #log_bin的值是binlog文件序列的基本名称
binlog_format     = ROW                #必须是ROW
binlog_row_image  = FULL            #必须是FULL
expire_logs_days  = 10                #依据实际情况而定

3. 准备数据库&表

   create database inventory;
   create table inventory.a (id bigint primary key auto_increment, name varchar(32));
   insert into inventory.a values (null, 'n1'),(null, 'n2'),(null, 'n3');

2. 编写程序

2.1. 工程依赖（Maven）

pom.xml

<dependency>
    <groupId>io.debezium</groupId>
    <artifactId>debezium-api</artifactId>
    <version>${version.debezium}</version>
</dependency>
<dependency>
    <groupId>io.debezium</groupId>
    <artifactId>debezium-embedded</artifactId>
    <version>${version.debezium}</version>
</dependency>

<dependency>
    <groupId>io.debezium</groupId>
    <artifactId>debezium-connector-mysql</artifactId>
    <version>${version.debezium}</version>
</dependency>

目前Debezium最新稳定版本为：1.9.5.Final

2.2. 准备数据库&表

create database inventory;
create table inventory.a (id bigint primary key, name varchar(32));
insert into inventory.a values (1, 'n1'),(2, 'n2'),(3, 'n3');

2.3. 代码编写

package com.greatdb.dbzdemo;

import java.io.IOException;
import java.util.Properties;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import io.debezium.engine.ChangeEvent;
import io.debezium.engine.DebeziumEngine;
import io.debezium.engine.format.Json;

/**
 * @author wang.jianwen
 * @version 1.0
 * @date 2022/07/29
 */
public class DebeziumTest {

    private static DebeziumEngine<ChangeEvent<String, String>> engine;

    public static void main(String[] args) throws Exception {
        final Properties props = new Properties();
        props.setProperty("name", "dbz-engine");
        props.setProperty("connector.class", "io.debezium.connector.mysql.MySqlConnector");

        //offset config begin - 使用文件来存储已处理的binlog偏移量
        props.setProperty("offset.storage", "org.apache.kafka.connect.storage.FileOffsetBackingStore");
        props.setProperty("offset.storage.file.filename", "/tmp/dbz/storage/mysql_offsets.dat");
        props.setProperty("offset.flush.interval.ms", "0");
        //offset config end

        props.setProperty("database.server.name", "mysql-connector");
        props.setProperty("database.history", "io.debezium.relational.history.FileDatabaseHistory");
        props.setProperty("database.history.file.filename", "/tmp/dbz/storage/mysql_dbhistory.txt");

        props.setProperty("database.server.id", "122112");    //需要与MySQL的server-id不同
        props.setProperty("database.hostname", "tmg");
        props.setProperty("database.port", "3306");
        props.setProperty("database.user", "mysqluser");
        props.setProperty("database.password", "mysqlpw");
        props.setProperty("database.include.list", "inventory");//要捕获的数据库名
        props.setProperty("table.include.list", "inventory.a");//要捕获的数据表

        props.setProperty("snapshot.mode", "initial");//全量+增量

        // 使用上述配置创建Debezium引擎，输出样式为Json字符串格式
        engine = DebeziumEngine.create(Json.class)
                .using(props)
                .notifying(record -> {
                    System.out.println(record);//输出到控制台
                })
                .using((success, message, error) -> {
                    if (error != null) {
                        // 报错回调
                        System.out.println("------------error, message:" + message + "exception:" + error);
                    }
                    closeEngine(engine);
                })
                .build();

        ExecutorService executor = Executors.newSingleThreadExecutor();
        executor.execute(engine);
        addShutdownHook(engine);
        awaitTermination(executor);

        System.out.println("------------main finished.");
    }

    private static void closeEngine(DebeziumEngine<ChangeEvent<String, String>> engine) {
        try {
            engine.close();
        } catch (IOException ignored) {
        }
    }

    private static void addShutdownHook(DebeziumEngine<ChangeEvent<String, String>> engine) {
        Runtime.getRuntime().addShutdownHook(new Thread(() -> closeEngine(engine)));
    }

    private static void awaitTermination(ExecutorService executor) {
        if (executor != null) {
            try {
                executor.shutdown();
                while (!executor.awaitTermination(5, TimeUnit.SECONDS)) {
                }
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
    }
}

3. 测试

程序跑起来后，可以看到控制台输出：

...（省略）
EmbeddedEngineChangeEvent [key={"schema":{"type":"struct","fields":[{"type":"int64","optional":false,"field":"id"}],"optional":false,"name":"mysql_connector.inventory.a.Key"},"payload":{"id":1}}, value={"schema":{"type":"struct","fields":[{"type":"struct","fields":[{"type":"int64","optional":false,"field":"id"},{"type":"string","optional":true,"field":"name"}],"optional":true,"name":"mysql_connector.inventory.a.Value","field":"before"},{"type":"struct","fields":[{"type":"int64","optional":false,"field":"id"},{"type":"string","optional":true,"field":"name"}],"optional":true,"name":"mysql_connector.inventory.a.Value","field":"after"},{"type":"struct","fields":[{"type":"string","optional":false,"field":"version"},{"type":"string","optional":false,"field":"connector"},{"type":"string","optional":false,"field":"name"},{"type":"int64","optional":false,"field":"ts_ms"},{"type":"string","optional":true,"name":"io.debezium.data.Enum","version":1,"parameters":{"allowed":"true,last,false,incremental"},"default":"false","field":"snapshot"},{"type":"string","optional":false,"field":"db"},{"type":"string","optional":true,"field":"sequence"},{"type":"string","optional":true,"field":"table"},{"type":"int64","optional":false,"field":"server_id"},{"type":"string","optional":true,"field":"gtid"},{"type":"string","optional":false,"field":"file"},{"type":"int64","optional":false,"field":"pos"},{"type":"int32","optional":false,"field":"row"},{"type":"int64","optional":true,"field":"thread"},{"type":"string","optional":true,"field":"query"}],"optional":false,"name":"io.debezium.connector.mysql.Source","field":"source"},{"type":"string","optional":false,"field":"op"},{"type":"int64","optional":true,"field":"ts_ms"},{"type":"struct","fields":[{"type":"string","optional":false,"field":"id"},{"type":"int64","optional":false,"field":"total_order"},{"type":"int64","optional":false,"field":"data_collection_order"}],"optional":true,"field":"transaction"}],"optional":false,"name":"mysql_connector.inventory.a.Envelope"},"payload":{"before":null,"after":{"id":1,"name":"n1"},"source":{"version":"1.8.1.Final","connector":"mysql","name":"mysql-connector","ts_ms":1659064005186,"snapshot":"true","db":"inventory","sequence":null,"table":"a","server_id":0,"gtid":null,"file":"mysql-bin.000001","pos":154,"row":0,"thread":null,"query":null},"op":"r","ts_ms":1659064005191,"transaction":null}}, sourceRecord=SourceRecord{sourcePartition={server=mysql-connector}, sourceOffset={ts_sec=1659064005, file=mysql-bin.000001, pos=154, snapshot=true}} ConnectRecord{topic='mysql-connector.inventory.a', kafkaPartition=null, key=Struct{id=1}, keySchema=Schema{mysql_connector.inventory.a.Key:STRUCT}, value=Struct{after=Struct{id=1,name=n1},source=Struct{version=1.8.1.Final,connector=mysql,name=mysql-connector,ts_ms=1659064005186,snapshot=true,db=inventory,table=a,server_id=0,file=mysql-bin.000001,pos=154,row=0},op=r,ts_ms=1659064005191}, valueSchema=Schema{mysql_connector.inventory.a.Envelope:STRUCT}, timestamp=null, headers=ConnectHeaders(headers=)}]
EmbeddedEngineChangeEvent [key={"schema":{"type":"struct","fields":[{"type":"int64","optional":false,"field":"id"}],"optional":false,"name":"mysql_connector.inventory.a.Key"},"payload":{"id":2}}, value={"schema":{"type":"struct","fields":[{"type":"struct","fields":[{"type":"int64","optional":false,"field":"id"},{"type":"string","optional":true,"field":"name"}],"optional":true,"name":"mysql_connector.inventory.a.Value","field":"before"},{"type":"struct","fields":[{"type":"int64","optional":false,"field":"id"},{"type":"string","optional":true,"field":"name"}],"optional":true,"name":"mysql_connector.inventory.a.Value","field":"after"},{"type":"struct","fields":[{"type":"string","optional":false,"field":"version"},{"type":"string","optional":false,"field":"connector"},{"type":"string","optional":false,"field":"name"},{"type":"int64","optional":false,"field":"ts_ms"},{"type":"string","optional":true,"name":"io.debezium.data.Enum","version":1,"parameters":{"allowed":"true,last,false,incremental"},"default":"false","field":"snapshot"},{"type":"string","optional":false,"field":"db"},{"type":"string","optional":true,"field":"sequence"},{"type":"string","optional":true,"field":"table"},{"type":"int64","optional":false,"field":"server_id"},{"type":"string","optional":true,"field":"gtid"},{"type":"string","optional":false,"field":"file"},{"type":"int64","optional":false,"field":"pos"},{"type":"int32","optional":false,"field":"row"},{"type":"int64","optional":true,"field":"thread"},{"type":"string","optional":true,"field":"query"}],"optional":false,"name":"io.debezium.connector.mysql.Source","field":"source"},{"type":"string","optional":false,"field":"op"},{"type":"int64","optional":true,"field":"ts_ms"},{"type":"struct","fields":[{"type":"string","optional":false,"field":"id"},{"type":"int64","optional":false,"field":"total_order"},{"type":"int64","optional":false,"field":"data_collection_order"}],"optional":true,"field":"transaction"}],"optional":false,"name":"mysql_connector.inventory.a.Envelope"},"payload":{"before":null,"after":{"id":2,"name":"n2"},"source":{"version":"1.8.1.Final","connector":"mysql","name":"mysql-connector","ts_ms":1659064005195,"snapshot":"true","db":"inventory","sequence":null,"table":"a","server_id":0,"gtid":null,"file":"mysql-bin.000001","pos":154,"row":0,"thread":null,"query":null},"op":"r","ts_ms":1659064005196,"transaction":null}}, sourceRecord=SourceRecord{sourcePartition={server=mysql-connector}, sourceOffset={ts_sec=1659064005, file=mysql-bin.000001, pos=154, snapshot=true}} ConnectRecord{topic='mysql-connector.inventory.a', kafkaPartition=null, key=Struct{id=2}, keySchema=Schema{mysql_connector.inventory.a.Key:STRUCT}, value=Struct{after=Struct{id=2,name=n2},source=Struct{version=1.8.1.Final,connector=mysql,name=mysql-connector,ts_ms=1659064005195,snapshot=true,db=inventory,table=a,server_id=0,file=mysql-bin.000001,pos=154,row=0},op=r,ts_ms=1659064005196}, valueSchema=Schema{mysql_connector.inventory.a.Envelope:STRUCT}, timestamp=null, headers=ConnectHeaders(headers=)}]
EmbeddedEngineChangeEvent [key={"schema":{"type":"struct","fields":[{"type":"int64","optional":false,"field":"id"}],"optional":false,"name":"mysql_connector.inventory.a.Key"},"payload":{"id":3}}, value={"schema":{"type":"struct","fields":[{"type":"struct","fields":[{"type":"int64","optional":false,"field":"id"},{"type":"string","optional":true,"field":"name"}],"optional":true,"name":"mysql_connector.inventory.a.Value","field":"before"},{"type":"struct","fields":[{"type":"int64","optional":false,"field":"id"},{"type":"string","optional":true,"field":"name"}],"optional":true,"name":"mysql_connector.inventory.a.Value","field":"after"},{"type":"struct","fields":[{"type":"string","optional":false,"field":"version"},{"type":"string","optional":false,"field":"connector"},{"type":"string","optional":false,"field":"name"},{"type":"int64","optional":false,"field":"ts_ms"},{"type":"string","optional":true,"name":"io.debezium.data.Enum","version":1,"parameters":{"allowed":"true,last,false,incremental"},"default":"false","field":"snapshot"},{"type":"string","optional":false,"field":"db"},{"type":"string","optional":true,"field":"sequence"},{"type":"string","optional":true,"field":"table"},{"type":"int64","optional":false,"field":"server_id"},{"type":"string","optional":true,"field":"gtid"},{"type":"string","optional":false,"field":"file"},{"type":"int64","optional":false,"field":"pos"},{"type":"int32","optional":false,"field":"row"},{"type":"int64","optional":true,"field":"thread"},{"type":"string","optional":true,"field":"query"}],"optional":false,"name":"io.debezium.connector.mysql.Source","field":"source"},{"type":"string","optional":false,"field":"op"},{"type":"int64","optional":true,"field":"ts_ms"},{"type":"struct","fields":[{"type":"string","optional":false,"field":"id"},{"type":"int64","optional":false,"field":"total_order"},{"type":"int64","optional":false,"field":"data_collection_order"}],"optional":true,"field":"transaction"}],"optional":false,"name":"mysql_connector.inventory.a.Envelope"},"payload":{"before":null,"after":{"id":3,"name":"n3"},"source":{"version":"1.8.1.Final","connector":"mysql","name":"mysql-connector","ts_ms":1659064005196,"snapshot":"last","db":"inventory","sequence":null,"table":"a","server_id":0,"gtid":null,"file":"mysql-bin.000001","pos":154,"row":0,"thread":null,"query":null},"op":"r","ts_ms":1659064005196,"transaction":null}}, sourceRecord=SourceRecord{sourcePartition={server=mysql-connector}, sourceOffset={ts_sec=1659064005, file=mysql-bin.000001, pos=154}} ConnectRecord{topic='mysql-connector.inventory.a', kafkaPartition=null, key=Struct{id=3}, keySchema=Schema{mysql_connector.inventory.a.Key:STRUCT}, value=Struct{after=Struct{id=3,name=n3},source=Struct{version=1.8.1.Final,connector=mysql,name=mysql-connector,ts_ms=1659064005196,snapshot=last,db=inventory,table=a,server_id=0,file=mysql-bin.000001,pos=154,row=0},op=r,ts_ms=1659064005196}, valueSchema=Schema{mysql_connector.inventory.a.Envelope:STRUCT}, timestamp=null, headers=ConnectHeaders(headers=)}]
...（省略）

可以看到全量的数据已经输出，关键的数据如下：

..."payload":{"before":null,"after":{"id":1,"name":"n1"}..."op":"r"...
..."payload":{"before":null,"after":{"id":2,"name":"n2"}..."op":"r"...
..."payload":{"before":null,"after":{"id":3,"name":"n3"}..."op":"r"...

• 接下来新增一条数据：

  insert into inventory.a values (4, 'n4');

  控制台输出：

  ..."payload":{"before":null,"after":{"id":4,"name":"n4"}..."op":"c"...

• 修改一条数据：

  update inventory.a set name = 'n4-upd' where id = 4;

  控制台输出：

  ..."payload":{"before":{"id":4,"name":"n4"},"after":{"id":4,"name":"n4-upd"}..."op":"u"...

• 删除一条数据：

  delete from inventory.a where id = 1;

  控制台输出：

  ..."payload":{"before":{"id":1,"name":"n1"},"after":null..."op":"d"...

  三、总结

  本文以MySQL为例介绍了Debezium在代码中基本使用流程，对MySQL的数据进行常见的增删改操作，Debezium将捕获这些数据行的变化，并记录了数据行变化前后的数据，并对外提供事件流，外部可以获取并对事件进行相应处理。

参考：https://debezium.io/documentation/reference/1.8/index.html