FlinkCDC实践

CDC介绍

CDC 是 Change Data Capture（变更数据获取）的简称。核心思想是，监测并捕获数据库的变动（包括数据或数据表的插入、更新以及删除等），将这些变更按发生的顺序完整记录下来，写入到消息中间件中以供其他服务进行订阅及消费。

CDC种类

基于查询的CDC

例如：Sqoop、JDBC source等产品。
特点：基于批处理，不能捕获到所有数据的变化、高延迟、需要查询数据库，会增加数据库压力

基于binlog的CDC

例如：Maxwell、Canal、Debezium
特点：基于streaming模式、能捕捉所有数据的变化、低延迟、不会增加数据库压力。

Flink-CDC

Flink 社区开发了flink-cdc-connectors组件，这是一个可以直接从MySQL、PostgreSQL
等数据库直接读取全量数据和增量变更数据的source组件。目前已开源。
开源地址：https://github.com/ververica/flink-cdc-connectors

Flink-CDC实践案例

1.开启mysql binlog

查看mysql-binlog状态并开启mysql-binlog

上图是开始的状态。如果没有开始，则log_bin=off，log_bin_basename和log_bin_index值为空。开启方式如下：

vim vim /etc/my.cnf

在添加以下信息

#开启binglog
server-id=1
log-bin=/var/lib/mysql/mysql-bin

server-id表示单个结点的id，这里由于只有一个结点，所以可以把id随机指定为一个数，这里将id设置成1。若集群中有多个结点，则id不能相同
第二句是指定binlog日志文件的名字为mysql-bin，以及其存储路径。
添加完成后保存退出。

重启mysql服务

service mysqld restart

查看binlog

2.建立mysql测试表并初始化数据

3.编写Flink-CDC代码

导入jar包

	<dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-java</artifactId>
            <version>1.12.0</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-streaming-java_2.12</artifactId>
            <version>1.12.0</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-clients_2.12</artifactId>
            <version>1.12.0</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-client</artifactId>
            <version>3.1.3</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba.ververica</groupId>
            <artifactId>flink-connector-mysql-cdc</artifactId>
            <version>1.2.0</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.75</version>
        </dependency>

编写测试类

package com.meijs;

import com.alibaba.ververica.cdc.connectors.mysql.MySQLSource;
import com.alibaba.ververica.cdc.connectors.mysql.table.StartupOptions;
import com.alibaba.ververica.cdc.debezium.DebeziumSourceFunction;
import com.alibaba.ververica.cdc.debezium.StringDebeziumDeserializationSchema;
import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;

public class FlinkCDC {
    public static void main(String args[]) throws Exception {
        //获取执行环境
        StreamExecutionEnvironment executionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment();
        executionEnvironment.setParallelism(1);

        DebeziumSourceFunction<String> sourceFunction = MySQLSource.<String>builder()
                .hostname("192.168.154.130")
                .port(3306)
                .username("root")
                .password("123456")
                .databaseList("test")
                .tableList("test.flink_cdc_test")//监控对应的表，如果没有该参数，则是监控全表
                .deserializer(new StringDebeziumDeserializationSchema())
                .startupOptions(StartupOptions.initial())//initial对监控的表做一个初始化快照，earliest,latest等参数与kafka的的offset类似
                .build();
        DataStreamSource<String> streamSource = executionEnvironment.addSource(sourceFunction);

        streamSource.print();

        executionEnvironment.execute("FlinkCDC");
    }
}

4.测试Flink-CDC

初始化执行后的打印结果如下：

SourceRecord{sourcePartition={server=mysql_binlog_source}, sourceOffset={file=mysql-bin.000005, pos=1353, row=1, snapshot=true}} ConnectRecord{topic='mysql_binlog_source.test.flink_cdc_test', kafkaPartition=null, key=Struct{id=1}, keySchema=Schema{mysql_binlog_source.test.flink_cdc_test.Key:STRUCT}, value=Struct{after=Struct{id=1,name=小米,log_url=www.xiaomi.com},source=Struct{version=1.4.1.Final,connector=mysql,name=mysql_binlog_source,ts_ms=0,snapshot=true,db=test,table=flink_cdc_test,server_id=0,file=mysql-bin.000005,pos=1353,row=0},op=c,ts_ms=1641905845597}, valueSchema=Schema{mysql_binlog_source.test.flink_cdc_test.Envelope:STRUCT}, timestamp=null, headers=ConnectHeaders(headers=)}
SourceRecord{sourcePartition={server=mysql_binlog_source}, sourceOffset={file=mysql-bin.000005, pos=1353, row=1, snapshot=true}} ConnectRecord{topic='mysql_binlog_source.test.flink_cdc_test', kafkaPartition=null, key=Struct{id=2}, keySchema=Schema{mysql_binlog_source.test.flink_cdc_test.Key:STRUCT}, value=Struct{after=Struct{id=2,name=华为,log_url=www.huawei.com},source=Struct{version=1.4.1.Final,connector=mysql,name=mysql_binlog_source,ts_ms=0,snapshot=true,db=test,table=flink_cdc_test,server_id=0,file=mysql-bin.000005,pos=1353,row=0},op=c,ts_ms=1641905845602}, valueSchema=Schema{mysql_binlog_source.test.flink_cdc_test.Envelope:STRUCT}, timestamp=null, headers=ConnectHeaders(headers=)}
SourceRecord{sourcePartition={server=mysql_binlog_source}, sourceOffset={file=mysql-bin.000005, pos=1353, row=1, snapshot=true}} ConnectRecord{topic='mysql_binlog_source.test.flink_cdc_test', kafkaPartition=null, key=Struct{id=3}, keySchema=Schema{mysql_binlog_source.test.flink_cdc_test.Key:STRUCT}, value=Struct{after=Struct{id=3,name=苹果,log_url=www.pingguo.com},source=Struct{version=1.4.1.Final,connector=mysql,name=mysql_binlog_source,ts_ms=0,snapshot=true,db=test,table=flink_cdc_test,server_id=0,file=mysql-bin.000005,pos=1353,row=0},op=c,ts_ms=1641905845602}, valueSchema=Schema{mysql_binlog_source.test.flink_cdc_test.Envelope:STRUCT}, timestamp=null, headers=ConnectHeaders(headers=)}
SourceRecord{sourcePartition={server=mysql_binlog_source}, sourceOffset={file=mysql-bin.000005, pos=1353}} ConnectRecord{topic='mysql_binlog_source.test.flink_cdc_test', kafkaPartition=null, key=Struct{id=4}, keySchema=Schema{mysql_binlog_source.test.flink_cdc_test.Key:STRUCT}, value=Struct{after=Struct{id=4,name=欧派,log_url=www.oppo.com},source=Struct{version=1.4.1.Final,connector=mysql,name=mysql_binlog_source,ts_ms=0,snapshot=last,db=test,table=flink_cdc_test,server_id=0,file=mysql-bin.000005,pos=1353,row=0},op=c,ts_ms=1641905845602}, valueSchema=Schema{mysql_binlog_source.test.flink_cdc_test.Envelope:STRUCT}, timestamp=null, headers=ConnectHeaders(headers=)}

op=c代表是创建，after为启动后当前的数据状态

更新一条数据观察打印结果

打印日志如下

SourceRecord{sourcePartition={server=mysql_binlog_source}, sourceOffset={ts_sec=1641906085, file=mysql-bin.000005, pos=1418, row=1, server_id=1, event=2}} ConnectRecord{topic='mysql_binlog_source.test.flink_cdc_test', kafkaPartition=null, key=Struct{id=4}, keySchema=Schema{mysql_binlog_source.test.flink_cdc_test.Key:STRUCT}, value=Struct{before=Struct{id=4,name=欧派,log_url=www.oppo.com},after=Struct{id=4,name=oppo,log_url=www.oppo.com},source=Struct{version=1.4.1.Final,connector=mysql,name=mysql_binlog_source,ts_ms=1641906085000,db=test,table=flink_cdc_test,server_id=1,file=mysql-bin.000005,pos=1553,row=0,thread=14},op=u,ts_ms=1641906085304}, valueSchema=Schema{mysql_binlog_source.test.flink_cdc_test.Envelope:STRUCT}, timestamp=null, headers=ConnectHeaders(headers=)}

op=u代表为update，before为修改更新前的数据，after更新后的数据状态

删除一条数据观察打印结果

SourceRecord{sourcePartition={server=mysql_binlog_source}, sourceOffset={ts_sec=1641906292, file=mysql-bin.000005, pos=1735, row=1, server_id=1, event=2}} ConnectRecord{topic='mysql_binlog_source.test.flink_cdc_test', kafkaPartition=null, key=Struct{id=3}, keySchema=Schema{mysql_binlog_source.test.flink_cdc_test.Key:STRUCT}, value=Struct{before=Struct{id=3,name=苹果,log_url=www.pingguo.com},source=Struct{version=1.4.1.Final,connector=mysql,name=mysql_binlog_source,ts_ms=1641906292000,db=test,table=flink_cdc_test,server_id=1,file=mysql-bin.000005,pos=1870,row=0,thread=14},op=d,ts_ms=1641906292636}, valueSchema=Schema{mysql_binlog_source.test.flink_cdc_test.Envelope:STRUCT}, timestamp=null, headers=ConnectHeaders(headers=)}

op=d代表为delete，before为修改更新前的数据，可以看到没after

在开启状态上增加一条数据观察打印结果

SourceRecord{sourcePartition={server=mysql_binlog_source}, sourceOffset={ts_sec=1641906490, file=mysql-bin.000005, pos=2030, row=1, server_id=1, event=2}} ConnectRecord{topic='mysql_binlog_source.test.flink_cdc_test', kafkaPartition=null, key=Struct{id=6}, keySchema=Schema{mysql_binlog_source.test.flink_cdc_test.Key:STRUCT}, value=Struct{after=Struct{id=6,name=kupai,log_url=www.kupai.com},source=Struct{version=1.4.1.Final,connector=mysql,name=mysql_binlog_source,ts_ms=1641906490000,db=test,table=flink_cdc_test,server_id=1,file=mysql-bin.000005,pos=2165,row=0,thread=14},op=c,ts_ms=1641906490308}, valueSchema=Schema{mysql_binlog_source.test.flink_cdc_test.Envelope:STRUCT}, timestamp=null, headers=ConnectHeaders(headers=)}

同时可以看出flink对bing-log的监控和mysql-binglog一致