Flink写出数据到 MySql 控制事务，保证Exactly_Once

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一、MySql Sink

要想使用TwoPhaseCommitSinkFunction，存储系统必须支持事务

Mysql Sink继承TwoPhaseCommitSinkFunction抽象类，分两个阶段提交Sink，保证Exactly_Once：

• ①做checkpoint
• ② 提交事务

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二、控制事务代码

1、主线代码

参数详解：

• ① 输入的类型
• ② connection数据库连接对象
• ③ 什么都不指定，为了泛型，写void

public class MySqlTwoPhaseCommitSink extends TwoPhaseCommitSinkFunction<Tuple2<String, Integer>,MySqlTwoPhaseCommitSink.ConnectionState, Void> {// 定义可用的构造函数public MySqlTwoPhaseCommitSink() {super(new KryoSerializer<>(MySqlTwoPhaseCommitSink.ConnectionState.class, new ExecutionConfig()),VoidSerializer.INSTANCE);}@Overrideprotected ConnectionState beginTransaction() throws Exception {System.out.println("=====> beginTransaction... ");//使用连接池，不使用单个连接//Class.forName("com.mysql.jdbc.Driver");//Connection conn = DriverManager.getConnection("jdbc:mysql://172.16.200// .101:3306/bigdata?characterEncoding=UTF-8", "root", "123456");Connection connection = DruidConnectionPool.getConnection();connection.setAutoCommit(false);//设定不自动提交return new ConnectionState(connection);}@Overrideprotected void invoke(ConnectionState transaction, Tuple2<String, Integer> value, Context context) throws Exception {Connection connection = transaction.connection;PreparedStatement pstm = connection.prepareStatement("INSERT INTO t_wordcount (word, counts) VALUES (?, ?) ON" +" DUPLICATE KEY UPDATE counts = ?");pstm.setString(1, value.f0);pstm.setInt(2, value.f1);pstm.setInt(3, value.f1);pstm.executeUpdate();pstm.close();}// 先不做处理@Overrideprotected void preCommit(ConnectionState transaction) throws Exception {System.out.println("=====> preCommit... " + transaction);}//提交事务@Overrideprotected void commit(ConnectionState transaction) {System.out.println("=====> commit... ");Connection connection = transaction.connection;try {connection.commit();connection.close();} catch (SQLException e) {throw new RuntimeException("提交事物异常");}}//回滚事务@Overrideprotected void abort(ConnectionState transaction) {System.out.println("=====> abort... ");Connection connection = transaction.connection;try {connection.rollback();connection.close();} catch (SQLException e) {throw new RuntimeException("回滚事物异常");}}//定义建立数据库连接的方法public static class ConnectionState {private final transient Connection connection;public ConnectionState(Connection connection) {this.connection = connection;}}
}

2、Druid 数据库连接池类

为什么要用连接池？

• 因为每个数据库连接都要控制事务

import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;public class DruidConnectionPool {private transient static DataSource dataSource = null;private transient static Properties props = new Properties();// 静态代码块static {props.put("driverClassName", "com.mysql.jdbc.Driver");props.put("url", "jdbc:mysql://localhost:3306/day01?characterEncoding=utf8");props.put("username", "root");props.put("password", "123456");try {dataSource = DruidDataSourceFactory.createDataSource(props);} catch (Exception e) {e.printStackTrace();}}private DruidConnectionPool() {}public static Connection getConnection() throws SQLException {return dataSource.getConnection();}
}

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