Flume-自定义 Source 读取 MySQL 数据

Posted 2020-11-16 江湖小小白

开源实现：https://github.com/keedio/flume-ng-sql-source

这里记录的是自己手动实现。

 

测试中要读取的表

CREATE TABLE `student` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) COLLATE utf8_bin DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 COLLATE=utf8_bin;

记录表（必须），告诉 Flume 每次从哪开始读取

CREATE TABLE `flume_meta` (
  `source_tab` varchar(255) COLLATE utf8_bin NOT NULL,
  `current_index` bigint(255) DEFAULT NULL,
  PRIMARY KEY (`source_tab`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;

 

一、编写自定义 Source

1.添加 pom 依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com</groupId>
    <artifactId>flume</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.apache.flume</groupId>
            <artifactId>flume-ng-core</artifactId>
            <version>1.9.0</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.27</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

2.编写类

MySQLSourceHelper，JDBC 工具类，主要是读取数据表和更新读取记录

package source;

import org.apache.flume.Context;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.math.BigInteger;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class MySQLSourceHelper {

    private static final Logger LOG = LoggerFactory.getLogger(MySQLSourceHelper.class);

    // 开始 id
    private String startFrom;
    private static final String DEFAULT_START_VALUE = "0";

    // 表名
    private String table;
    // 用户传入的查询的列
    private String columnsToSelect;
    private static final String DEFAULT_Columns_To_Select = "*";

    private static String dbUrl, dbUser, dbPassword, dbDriver;
    private static Connection conn = null;
    private static PreparedStatement ps = null;

    // 获取 JDBC 连接
    private static Connection getConnection() {
        try {
            Class.forName(dbDriver);
            return DriverManager.getConnection(dbUrl, dbUser, dbPassword);
        } catch (SQLException | ClassNotFoundException e) {
            e.printStackTrace();
        }
        return null;
    }

    // 构造方法
    MySQLSourceHelper(Context context) {
        // 有默认值参数：获取 flume 任务配置文件中的参数，读不到的采用默认值
        this.startFrom = context.getString("start.from", DEFAULT_START_VALUE);
        this.columnsToSelect = context.getString("columns.to.select", DEFAULT_Columns_To_Select);

        // 无默认值参数：获取 flume 任务配置文件中的参数
        this.table = context.getString("table");

        dbUrl = context.getString("db.url");
        dbUser = context.getString("db.user");
        dbPassword = context.getString("db.password");
        dbDriver = context.getString("db.driver");
        conn = getConnection();
    }

    // 构建 sql 语句，以 id 作为 offset
    private String buildQuery() {
        StringBuilder execSql = new StringBuilder("select " + columnsToSelect + " from " + table);
        return execSql.append(" where id ").append("> ").append(getStatusDBIndex(startFrom)).toString();
    }

    // 执行查询
    List<List<Object>> executeQuery() {
        try {
            // 每次执行查询时都要重新生成 sql，因为 id 不同
            String customQuery = buildQuery();
            // 存放结果的集合
            List<List<Object>> results = new ArrayList<>();

            ps = conn.prepareStatement(customQuery);
            ResultSet result = ps.executeQuery(customQuery);
            while (result.next()) {
                // 存放一条数据的集合（多个列）
                List<Object> row = new ArrayList<>();
                // 将返回结果放入集合
                for (int i = 1; i <= result.getMetaData().getColumnCount(); i++) {
                    row.add(result.getObject(i));
                }
                results.add(row);
            }
            LOG.info("execSql:" + customQuery + "\\tresultSize:" + results.size());
            return results;
        } catch (SQLException e) {
            LOG.error(e.toString());
            // 重新连接
            conn = getConnection();
        }
        return null;
    }

    // 将结果集转化为字符串，每一条数据是一个 list 集合，将每一个小的 list 集合转化为字符串
    List<String> getAllRows(List<List<Object>> queryResult) {
        List<String> allRows = new ArrayList<>();
        StringBuilder row = new StringBuilder();
        for (List<Object> rawRow : queryResult) {
            for (Object aRawRow : rawRow) {
                if (aRawRow == null) {
                    row.append(",");
                } else {
                    row.append(aRawRow.toString()).append(",");
                }
            }
            allRows.add(row.toString());
            row = new StringBuilder();
        }
        return allRows;
    }

    // 更新 offset 元数据状态，每次返回结果集后调用。必须记录每次查询的 offset 值，为程序中断续跑数据时使用，以 id 为 offset
    void updateOffset2DB(BigInteger size) {
        try {
            // 以 source_tab 做为 KEY，如果不存在则插入，存在则更新（每个源表对应一条记录）
            String sql = "insert into flume_meta VALUES(\'" + table + "\',\'" + size + "\') on DUPLICATE key update current_index=\'" + size + "\'";
            LOG.info("updateStatus Sql:" + sql);
            ps = conn.prepareStatement(sql);
            ps.execute();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 从 flume_meta 表中查询出当前的 id 是多少
    private BigInteger getStatusDBIndex(String startFrom) {
        BigInteger dbIndex = new BigInteger(startFrom);
        try {
            ps = conn.prepareStatement("select current_index from flume_meta where source_tab=\'" + table + "\'");
            ResultSet result = ps.executeQuery();
            if (result.next()) {
                String id = result.getString(1);
                if (id != null) {
                    dbIndex = new BigInteger(id);
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        // 如果没有数据，则说明是第一次查询或者数据表中还没有存入数据，返回最初传入的值
        return dbIndex;
    }

    // 关闭相关资源
    void close() {
        try {
            ps.close();
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public String getTable() {
        return table;
    }
}

MySQLSource，自定义 Source 类

package source;

import org.apache.flume.Context;
import org.apache.flume.Event;
import org.apache.flume.EventDeliveryException;
import org.apache.flume.PollableSource;
import org.apache.flume.conf.Configurable;
import org.apache.flume.event.SimpleEvent;
import org.apache.flume.source.AbstractSource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class MySQLSource extends AbstractSource implements Configurable, PollableSource {

    // 打印日志
    private static final Logger LOG = LoggerFactory.getLogger(MySQLSource.class);

    // sqlHelper
    private MySQLSourceHelper sqlSourceHelper;

    // 两次查询的时间间隔
    private int queryDelay;
    private static final int DEFAULT_QUERY_DELAY = 10000;

    @Override
    public long getBackOffSleepIncrement() {
        return 0;
    }

    @Override
    public long getMaxBackOffSleepInterval() {
        return 0;
    }

    @Override
    public void configure(Context context) {
        // 初始化
        sqlSourceHelper = new MySQLSourceHelper(context);
        queryDelay = context.getInteger("query.delay", DEFAULT_QUERY_DELAY);
    }

    @Override
    public Status process() throws EventDeliveryException {
        try {
            // 存放 event 的集合
            List<Event> events = new ArrayList<>();
            // 存放 event 头集合
            HashMap<String, String> header = new HashMap<>();
            header.put("table", sqlSourceHelper.getTable());

            // 查询数据表
            List<List<Object>> result = sqlSourceHelper.executeQuery();
            // 如果有返回数据，则将数据封装为 event
            if (!result.isEmpty()) {
                List<String> allRows = sqlSourceHelper.getAllRows(result);
                Event event = null;
                for (String row : allRows) {
                    event = new SimpleEvent();
                    event.setHeaders(header);
                    event.setBody(row.getBytes());
                    events.add(event);
                }
                // 将 event 写入 channel
                getChannelProcessor().processEventBatch(events);
                // 更新数据表中的 offset 信息，取最后一条数据的第一列（id 列）
                sqlSourceHelper.updateOffset2DB(new BigInteger(result.get(result.size()-1).get(0).toString()));
            }
            // 等待时长
            Thread.sleep(queryDelay);
            return Status.READY;
        } catch (InterruptedException e) {
            LOG.error("Error procesing row", e);
            return Status.BACKOFF;
        }
    }

    @Override
    public synchronized void stop() {
        LOG.info("Stopping sql source {} ...", getName());
        try {
            sqlSourceHelper.close();
        } finally {
            super.stop();
        }
    }
}

 

二、打包测试

1.打包上传

记得把 pom 依赖中的 MySQL 的 jar 包也传上去。

参考：https://www.cnblogs.com/jhxxb/p/11582804.html

2.编写 flume 配置文件

mysql.conf

# Name the components on this agent
a1.sources = r1
a1.sinks = k1
a1.channels = c1

# Describe/configure the source
a1.sources.r1.type = source.MySQLSource
a1.sources.r1.db.driver = com.mysql.jdbc.Driver
a1.sources.r1.db.url = jdbc:mysql://192.168.8.136:3306/rbac0
a1.sources.r1.db.user = root
a1.sources.r1.db.password = root
a1.sources.r1.table = student
# a1.sources.r1.columns.to.select = *
# a1.sources.r1.start.from = 0

# Describe the sink
a1.sinks.k1.type = logger

# Describe the channel
a1.channels.c1.type = memory
a1.channels.c1.capacity = 1000
a1.channels.c1.transactionCapacity = 100

# Bind the source and sink to the channel
a1.sources.r1.channels = c1
a1.sinks.k1.channel = c1

启动

cd /opt/apache-flume-1.9.0-bin

bin/flume-ng agent --conf conf/ --name a1 --conf-file /tmp/flume-job/mysql.conf -Dflume.root.logger=INFO,console

向监控表插入数据

INSERT student VALUES(NULL,\'zhangsan\',18);

Flume 的控制台日志