大數據-業務數據採集-FlinkCDC

CDC

CDC 是 Change Data Capture(變更數據獲取)的簡稱。核心思想是，監測並捕獲資料庫的變動（包括數據或數據表的插入、更新以及刪除等），將這些變更按發生的順序完整記錄下來，寫入到消息中間件中以供其他服務進行訂閱及消費。

CDC 的種類

CDC 主要分為基於查詢和基於 Binlog 兩種方式，我們主要瞭解一下這兩種之間的區別：

FlinkCDC

Flink 社區開發了 flink-cdc-connectors 組件，這是一個可以直接從 MySQL、PostgreSQL 等資料庫直接讀取【全量數據】和【增量變更數據】的 source 組件。而不需要使用類似 Kafka 之類的中間件中轉數據
目前也已開源，開源地址：https://github.com/ververica/flink-cdc-connectors

DataStream:

• 優點： 多庫多表
• 缺點： 需要自定義反序列化器（但靈活）
  FlinkSQL:
• 優點： 不需要自定義反序列化器
• 缺點： 單表

Demo

註意開啟 binlog_format=ROW
my.ini

log-bin=mysql-bin
#binlog_format="STATEMENT"
binlog_format="ROW"
#binlog_format="MIXED"
#service-id=1

POM

  <dependencies>
        <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>

        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-table-planner-blink_2.12</artifactId>
            <version>1.12.0</version>
        </dependency>
    </dependencies>

基於 DataStream

CustomerDeserialization.java

package com.vipsoft;

import com.alibaba.fastjson.JSONObject;
import com.alibaba.ververica.cdc.debezium.DebeziumDeserializationSchema;
import io.debezium.data.Envelope;
import org.apache.flink.api.common.typeinfo.BasicTypeInfo;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.util.Collector;
import org.apache.kafka.connect.data.Field;
import org.apache.kafka.connect.data.Schema;
import org.apache.kafka.connect.data.Struct;
import org.apache.kafka.connect.source.SourceRecord;

import java.util.List;

public class CustomerDeserialization implements DebeziumDeserializationSchema<String> {

    /**
     * 封裝的數據格式
     * {
     * "database":"",
     * "tableName":"",
     * "before":{"id":"","tm_name":""....},
     * "after":{"id":"","tm_name":""....},
     * "type":"c u d",
     * //"ts":156456135615
     * }
     */
    @Override
    public void deserialize(SourceRecord sourceRecord, Collector<String> collector) throws Exception {

        //1.創建JSON對象用於存儲最終數據
        JSONObject result = new JSONObject();

        //2.獲取庫名&表名
        String topic = sourceRecord.topic();
        String[] fields = topic.split("\\.");
        String database = fields[1];
        String tableName = fields[2];

        Struct value = (Struct) sourceRecord.value();
        //3.獲取"before"數據
        Struct before = value.getStruct("before");
        JSONObject beforeJson = new JSONObject();
        if (before != null) {
            Schema beforeSchema = before.schema();
            List<Field> beforeFields = beforeSchema.fields();
            for (Field field : beforeFields) {
                Object beforeValue = before.get(field);
                beforeJson.put(field.name(), beforeValue);
            }
        }

        //4.獲取"after"數據
        Struct after = value.getStruct("after");
        JSONObject afterJson = new JSONObject();
        if (after != null) {
            Schema afterSchema = after.schema();
            List<Field> afterFields = afterSchema.fields();
            for (Field field : afterFields) {
                Object afterValue = after.get(field);
                afterJson.put(field.name(), afterValue);
            }
        }

        //5.獲取操作類型  CREATE UPDATE DELETE
        Envelope.Operation operation = Envelope.operationFor(sourceRecord);
        String type = operation.toString().toLowerCase();
        if ("create".equals(type)) {
            type = "insert";
        }

        //6.將欄位寫入JSON對象
        result.put("database", database);
        result.put("tableName", tableName);
        result.put("before", beforeJson);
        result.put("after", afterJson);
        result.put("type", type);

        //7.輸出數據
        collector.collect(result.toJSONString());

    }

    @Override
    public TypeInformation<String> getProducedType() {
        return BasicTypeInfo.STRING_TYPE_INFO;
    }
}

FlinkCDC.java

package com.vipsoft;

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 {

        //1.獲取執行環境
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        env.setParallelism(1);

        //2.通過FlinkCDC構建SourceFunction並讀取數據
        DebeziumSourceFunction<String> sourceFunction = MySQLSource.<String>builder()
                .hostname("localhost")
                .serverTimeZone("GMT+8")  //時區報錯增加這個設置
                .port(3306)
                .username("root")
                .password("110")
                .databaseList("springboot")
                .tableList("springboot.sys_user")   //如果不添加該參數,則消費指定資料庫中所有表的數據.如果指定,指定方式為db.table
                //.deserializer(new StringDebeziumDeserializationSchema())
                .deserializer(new CustomerDeserialization()) //使用自定義反序列化器
                .startupOptions(StartupOptions.initial())
                .build();
        DataStreamSource<String> streamSource = env.addSource(sourceFunction);

        //3.列印數據
        streamSource.print();

        //4.啟動任務
        env.execute("FlinkCDC");

    }
}

運行效果

• 預設 StringDebeziumDeserializationSchema
  
• 自定義反序列化器
  

FlinkSQL

package com.vipsoft;

import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.table.api.Table;
import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
import org.apache.flink.types.Row;

public class FlinkCDCWithSQL {

    public static void main(String[] args) throws Exception {

        //1.獲取執行環境
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        env.setParallelism(1);
        StreamTableEnvironment tableEnv = StreamTableEnvironment.create(env);

        //2.DDL方式建表
        tableEnv.executeSql("CREATE TABLE mysql_binlog ( " +
                " id STRING NOT NULL, " +
                " username STRING, " +
                " nick_name STRING " +
                ") WITH ( " +
                " 'connector' = 'mysql-cdc', " +
                " 'hostname' = 'localhost', " +
                " 'port' = '3306', " +
                " 'username' = 'root', " +
                " 'password' = '110', " +
                " 'database-name' = 'springboot', " +
                " 'table-name' = 'sys_user' " +
                ")");

        //3.查詢數據
        Table table = tableEnv.sqlQuery("select * from mysql_binlog");

        //4.將動態表轉換為流
        DataStream<Tuple2<Boolean, Row>> retractStream = tableEnv.toRetractStream(table, Row.class);
        retractStream.print();

        //5.啟動任務
        env.execute("FlinkCDCWithSQL");
    }
}

運行效果

對比

通過對比，FlinkCDC 最舒服

插入對比

插入兩條數據

INSER INTO z_user_info VALUES(30,'zhang3','13800000000'),(31,'li4','13999999999')

FlinkCDC 每條變化都會產生一條 json

Maxwell 每條變化都會產生一條 json

Canal 一次性執行的SQL，會產生一條JSON（兩條數據組合在一起）【不方便，需要炸開解析】

更新對比

UPDATE z_user_info SET user_name='wang5' WHERE id IN(30,31)

FlinkCDC 包括了修改前的 before 數據

Maxwell 不包括修改前的數據

Canal 仍然是一條json

刪除對比

DELETE FROM z_user_info WHERE id IN(30,31)

FlinkCDC 兩條刪除的 json 數據

Maxwell

Canal

【尚矽谷】Flink數據倉庫視頻教程