四、实践案例——自定义MySQLSource案例
1、概述
实时监控MySQL，从MySQL中获取数据传输到HDFS或者其他存储框架，所以此时需要我们自己实现MySQLSource。
官方也提供了自定义source的接口：https://flume.apache.org/FlumeDeveloperGuide.html#source
2、自定义MySQLSource组成
3、自定义MySQLSource步骤
根据官方说明自定义mysqlsource需要继承AbstractSource类并实现Configurable和PollableSource接口。
实现相应方法：
getBackOffSleepIncrement() //暂不用
getMaxBackOffSleepInterval() //暂不用
configure(Context context) //初始化context
process() //获取数据（从mysql获取数据，业务处理比较复杂，所以定义一个专门的类——SQLSourceHelper来处理跟mysql的交互），封装成event并写入channel，这个方法被循环调用
stop() //关闭相关的资源
PollableSource：从source中提取数据，将其发送到channel。
Configurable：实现了Configurable的任何类都含有一个context，使用context获取配置信息。
4、代码实现
1）导入pom依赖
<dependencies>
<dependency>
<groupId>org.apache.flume</groupId>
<artifactId>flume-ng-core</artifactId>
<version>1.7.0</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.27</version>
</dependency>
</dependencies>
2）添加配置信息
在classpath下添加jdbc.properties和log4j.properties
jdbc.properties:
dbDriver=com.mysql.jdbc.Driver
dbUrl=jdbc:mysql://hadoop102:3306/mysqlsource?useUnicode=true&characterEncoding=utf-8
dbUser=root
dbPassword=000000
log4j.properties:
#--------console-----------
log4j.rootLogger=info,myconsole,myfile
log4j.appender.myconsole=org.apache.log4j.ConsoleAppender
log4j.appender.myconsole.layout=org.apache.log4j.SimpleLayout
#log4j.appender.myconsole.layout.ConversionPattern =%d [%t] %-5p [%c] - %m%n
#log4j.rootLogger=error,myfile
log4j.appender.myfile=org.apache.log4j.DailyRollingFileAppender
log4j.appender.myfile.File=/tmp/flume.log
log4j.appender.myfile.layout=org.apache.log4j.PatternLayout
log4j.appender.myfile.layout.ConversionPattern =%d [%t] %-5p [%c] - %m%n
3）SQLSourceHelper
属性说明：
方法说明：
代码实现：
package com.source;
import org.apache.flume.Context;
import org.apache.flume.conf.ConfigurationException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.sql.*;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
public class SQLSourceHelper {
private static final Logger LOG = LoggerFactory.getLogger(SQLSourceHelper.class);
private int runQueryDelay, //两次查询的时间间隔
startFrom, //开始id
currentIndex, //当前id
recordSixe = 0, //每次查询返回结果的条数
maxRow; //每次查询的最大条数
private String table, //要操作的表
columnsToSelect, //用户传入的查询的列
customQuery, //用户传入的查询语句
query, //构建的查询语句
defaultCharsetResultSet;//编码集
//上下文，用来获取配置文件
private Context context;
//为定义的变量赋值（默认值），可在flume任务的配置文件中修改
private static final int DEFAULT_QUERY_DELAY = 10000;
private static final int DEFAULT_START_VALUE = 0;
private static final int DEFAULT_MAX_ROWS = 2000;
private static final String DEFAULT_COLUMNS_SELECT = "*";
private static final String DEFAULT_CHARSET_RESULTSET = "UTF-8";
private static Connection conn = null;
private static PreparedStatement ps = null;
private static String connectionURL, connectionUserName, connectionPassword;
//加载静态资源
static {
Properties p = new Properties();
try {
p.load(SQLSourceHelper.class.getClassLoader().getResourceAsStream("jdbc.properties"));
connectionURL = p.getProperty("dbUrl");
connectionUserName = p.getProperty("dbUser");
connectionPassword = p.getProperty("dbPassword");
Class.forName(p.getProperty("dbDriver"));
} catch (IOException | ClassNotFoundException e) {
LOG.error(e.toString());
}
}
//获取JDBC连接
private static Connection InitConnection(String url, String user, String pw) {
try {
Connection conn = DriverManager.getConnection(url, user, pw);
if (conn == null)
throw new SQLException();
return conn;
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
//构造方法
SQLSourceHelper(Context context) throws ParseException {
//初始化上下文
this.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.columnsToSelect = context.getString("columns.to.select", DEFAULT_COLUMNS_SELECT);
this.runQueryDelay = context.getInteger("run.query.delay", DEFAULT_QUERY_DELAY);
this.startFrom = context.getInteger("start.from", DEFAULT_START_VALUE);
this.defaultCharsetResultSet = context.getString("default.charset.resultset", DEFAULT_CHARSET_RESULTSET);
//无默认值参数：获取flume任务配置文件中的参数
this.table = context.getString("table");
this.customQuery = context.getString("custom.query");
connectionURL = context.getString("connection.url");
connectionUserName = context.getString("connection.user");
connectionPassword = context.getString("connection.password");
conn = InitConnection(connectionURL, connectionUserName, connectionPassword);
//校验相应的配置信息，如果没有默认值的参数也没赋值，抛出异常
checkMandatoryProperties();
//获取当前的id
currentIndex = getStatusDBIndex(startFrom);
//构建查询语句
query = buildQuery();
}
//校验相应的配置信息（表，查询语句以及数据库连接的参数）
private void checkMandatoryProperties() {
if (table == null) {
throw new ConfigurationException("property table not set");
}
if (connectionURL == null) {
throw new ConfigurationException("connection.url property not set");
}
if (connectionUserName == null) {
throw new ConfigurationException("connection.user property not set");
}
if (connectionPassword == null) {
throw new ConfigurationException("connection.password property not set");
}
}
//构建sql语句
private String buildQuery() {
String sql = "";
//获取当前id
currentIndex = getStatusDBIndex(startFrom);
LOG.info(currentIndex + "");
if (customQuery == null) {
sql = "SELECT " + columnsToSelect + " FROM " + table;
} else {
sql = customQuery;
}
StringBuilder execSql = new StringBuilder(sql);
//以id作为offset
if (!sql.contains("where")) {
execSql.append(" where ");
execSql.append("id").append(">").append(currentIndex);
return execSql.toString();
} else {
int length = execSql.toString().length();
return execSql.toString().substring(0, length - String.valueOf(currentIndex).length()) + currentIndex;
}
}
//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
customQuery = buildQuery();
//存放结果的集合
List<List<Object>> results = new ArrayList<>();
if (ps == null) {
//
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 + "\nresultSize:" + results.size());
return results;
} catch (SQLException e) {
LOG.error(e.toString());
// 重新连接
conn = InitConnection(connectionURL, connectionUserName, connectionPassword);
}
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<>();
if (queryResult == null || queryResult.isEmpty())
return allRows;
StringBuilder row = new StringBuilder();
for (List<Object> rawRow : queryResult) {
Object value = null;
for (Object aRawRow : rawRow) {
value = aRawRow;
if (value == 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(int size) {
//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(source_tab,currentIndex) VALUES('"
+ this.table
+ "','" + (recordSixe += size)
+ "') on DUPLICATE key update source_tab=values(source_tab),currentIndex=values(currentIndex)";
LOG.info("updateStatus Sql:" + sql);
execSql(sql);
}
//执行sql语句
private void execSql(String sql) {
try {
ps = conn.prepareStatement(sql);
LOG.info("exec::" + sql);
ps.execute();
} catch (SQLException e) {
e.printStackTrace();
}
}
//获取当前id的offset
private Integer getStatusDBIndex(int startFrom) {
//从flume_meta表中查询出当前的id是多少
String dbIndex = queryOne("select currentIndex from flume_meta where source_tab='" + table + "'");
if (dbIndex != null) {
return Integer.parseInt(dbIndex);
}
//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 startFrom;
}
//查询一条数据的执行语句(当前id)
private String queryOne(String sql) {
ResultSet result = null;
try {
ps = conn.prepareStatement(sql);
result = ps.executeQuery();
while (result.next()) {
return result.getString(1);
}
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
//关闭相关资源
void close() {
try {
ps.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
int getCurrentIndex() {
return currentIndex;
}
void setCurrentIndex(int newValue) {
currentIndex = newValue;
}
int getRunQueryDelay() {
return runQueryDelay;
}
String getQuery() {
return query;
}
String getConnectionURL() {
return connectionURL;
}
private boolean isCustomQuerySet() {
return (customQuery != null);
}
Context getContext() {
return context;
}
public String getConnectionUserName() {
return connectionUserName;
}
public String getConnectionPassword() {
return connectionPassword;
}
String getDefaultCharsetResultSet() {
return defaultCharsetResultSet;
}
}
4）MySQLSource
package com.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.text.ParseException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class SQLSource extends AbstractSource implements Configurable, PollableSource {
//打印日志
private static final Logger LOG = LoggerFactory.getLogger(SQLSource.class);
//定义sqlHelper
private SQLSourceHelper sqlSourceHelper;
public long getBackOffSleepIncrement() {
return 0;
}
public long getMaxBackOffSleepInterval() {
return 0;
}
public void configure(Context context) {
try {
//初始化
sqlSourceHelper = new SQLSourceHelper(context);
} catch (ParseException e) {
e.printStackTrace();
}
}
public Status process() throws EventDeliveryException {
try {
//查询数据表
List<List<Object>> result = sqlSourceHelper.executeQuery();
//存放event的集合
List<Event> events = new ArrayList<>();
//存放event头集合
HashMap<String, String> header = new HashMap<>();
//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.setBody(row.getBytes());
event.setHeaders(header);
events.add(event);
}
//将event写入channel
this.getChannelProcessor().processEventBatch(events);
//更新数据表中的offset信息
sqlSourceHelper.updateOffset2DB(result.size());
}
//等待时长
Thread.sleep(sqlSourceHelper.getRunQueryDelay());
return Status.READY;
} catch (InterruptedException e) {
LOG.error("Error procesing row", e);
return Status.BACKOFF;
}
}
public synchronized void stop() {
LOG.info("Stopping sql source {} ...", getName());
try {
//关闭资源
sqlSourceHelper.close();
} finally {
super.stop();
}
}
}
5、测试
1）jar包准备
（1）将mysql驱动包放入flume的lib目录下
（2）打包项目并将jar包放入flume的lib目录下
2）配置文件准备
创建配置文件mysql.canf
# Name the components on this agent
a1.sources = r1
a1.sinks = k1
a1.channels = c1
# Describe/configure the source
a1.sources.r1.type = com.atguigu.source.SQLSource
a1.sources.r1.connection.url = jdbc:mysql://192.168.1.102:3306/mysqlsource
a1.sources.r1.connection.user = root
a1.sources.r1.connection.password = 000000
a1.sources.r1.table = student
a1.sources.r1.columns.to.select = *
a1.sources.r1.run.query.delay=5000
# 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
3）MySQL表准备
（1）创建mysqlsource数据库
CREATE DATABASE mysqlsource；
（2）在mysqlsource数据库下创建数据表student和元数据表flume_meta
CREATE TABLE `student` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
);
CREATE TABLE `flume_meta` (
`source_tab` varchar(255) NOT NULL,
`currentIndex` varchar(255) NOT NULL,
PRIMARY KEY (`source_tab`)
);
（3）向数据表中添加数据
1 zhangsan
2 lisi
3 wangwu
4 zhaoliu
（4）测试
bin/flume-ng agent --conf conf/ --name a1 --conf-file job/mysql.conf -Dflume.root.logger=INFO,console
