问题导读
1.hadoop mapreduce的通过哪两个类可以读取数据源?
2.如果没有mysql驱动包,一般会是什么问题?
3.如何添加包?
有时候我们在项目中会遇到输入结果集很大,但是输出结果很小,比如一些 pv、uv 数据,然后为了实时查询的需求,或者一些 OLAP 的需求,我们需要 mapreduce 与 mysql 进行数据的交互,而这些特性正是 hbase 或者 hive 目前亟待改进的地方。
好了言归正传,简单的说说背景、原理以及需要注意的地方:
1、为了方便 MapReduce 直接访问关系型数据库(Mysql,Oracle),Hadoop提供了DBInputFormat和DBOutputFormat两个类。通过DBInputFormat类把数据库表数据读入到HDFS,根据DBOutputFormat类把MapReduce产生的结果集导入到数据库表中。
2、由于0.20版本对DBInputFormat和DBOutputFormat支持不是很好,该例用了0.19版本来说明这两个类的用法。
至少在我的 0.20.203 中的 org.apache.hadoop.mapreduce.lib 下是没见到 db 包,所以本文也是以老版的 API 来为例说明的。
3、运行MapReduce时候报错:java.io.IOException: com.mysql.jdbc.Driver,一般是由于程序找不到mysql驱动包。解决方法是让每个tasktracker运行MapReduce程序时都可以找到该驱动包。
添加包有两种方式:
(1)在每个节点下的${HADOOP_HOME}/lib下添加该包。重启集群,一般是比较原始的方法。
(2)a)把包传到集群上: hadoop fs -put mysql-connector-java-5.1.0- bin.jar /hdfsPath/
b)在mr程序提交job前,添加语句:DistributedCache.addFileToClassPath(new Path(“/hdfsPath/mysql- connector-java- 5.1.0-bin.jar”), conf);
(3)虽然API用的是0.19的,但是使用0.20的API一样可用,只是会提示方法已过时而已。、
4、测试数据:
- CREATE TABLE `t` (
- `id` int DEFAULT NULL,
- `name` varchar(10) DEFAULT NULL
- ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-
- CREATE TABLE `t2` (
- `id` int DEFAULT NULL,
- `name` varchar(10) DEFAULT NULL
- ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-
- insert into t values (1,"june"),(2,"decli"),(3,"hello"),
- (4,"june"),(5,"decli"),(6,"hello"),(7,"june"),
- (8,"decli"),(9,"hello"),(10,"june"),
- (11,"june"),(12,"decli"),(13,"hello");
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5、代码:
- import java.io.DataInput;
- import java.io.DataOutput;
- import java.io.IOException;
- import java.sql.PreparedStatement;
- import java.sql.ResultSet;
- import java.sql.SQLException;
- import java.util.Iterator;
-
- import org.apache.hadoop.filecache.DistributedCache;
- import org.apache.hadoop.fs.Path;
- import org.apache.hadoop.io.LongWritable;
- import org.apache.hadoop.io.Text;
- import org.apache.hadoop.io.Writable;
- import org.apache.hadoop.mapred.JobClient;
- import org.apache.hadoop.mapred.JobConf;
- import org.apache.hadoop.mapred.MapReduceBase;
- import org.apache.hadoop.mapred.Mapper;
- import org.apache.hadoop.mapred.OutputCollector;
- import org.apache.hadoop.mapred.Reducer;
- import org.apache.hadoop.mapred.Reporter;
- import org.apache.hadoop.mapred.lib.IdentityReducer;
- import org.apache.hadoop.mapred.lib.db.DBConfiguration;
- import org.apache.hadoop.mapred.lib.db.DBInputFormat;
- import org.apache.hadoop.mapred.lib.db.DBOutputFormat;
- import org.apache.hadoop.mapred.lib.db.DBWritable;
-
- /**
- * Function: 测试 mr 与 mysql 的数据交互,此测试用例将一个表中的数据复制到另一张表中
- * 实际当中,可能只需要从 mysql 读,或者写到 mysql 中。
- * date: 2013-7-29 上午2:34:04 <br/>
- * @author june
- */
- public class Mysql2Mr {
- // DROP TABLE IF EXISTS `hadoop`.`studentinfo`;
- // CREATE TABLE studentinfo (
- // id INTEGER NOT NULL PRIMARY KEY,
- // name VARCHAR(32) NOT NULL);
-
- public static class StudentinfoRecord implements Writable, DBWritable {
- int id;
- String name;
-
- public StudentinfoRecord() {
-
- }
-
- public void readFields(DataInput in) throws IOException {
- this.id = in.readInt();
- this.name = Text.readString(in);
- }
-
- public String toString() {
- return new String(this.id + " " + this.name);
- }
-
- @Override
- public void write(PreparedStatement stmt) throws SQLException {
- stmt.setInt(1, this.id);
- stmt.setString(2, this.name);
- }
-
- @Override
- public void readFields(ResultSet result) throws SQLException {
- this.id = result.getInt(1);
- this.name = result.getString(2);
- }
-
- @Override
- public void write(DataOutput out) throws IOException {
- out.writeInt(this.id);
- Text.writeString(out, this.name);
- }
- }
-
- // 记住此处是静态内部类,要不然你自己实现无参构造器,或者等着抛异常:
- // Caused by: java.lang.NoSuchMethodException: DBInputMapper.<init>()
- // http://*.com/questions/7154125/custom-mapreduce-input-format-cant-find-constructor
- // 网上脑残式的转帖,没见到一个写对的。。。
- public static class DBInputMapper extends MapReduceBase implements
- Mapper<LongWritable, StudentinfoRecord, LongWritable, Text> {
- public void map(LongWritable key, StudentinfoRecord value,
- OutputCollector<LongWritable, Text> collector, Reporter reporter) throws IOException {
- collector.collect(new LongWritable(value.id), new Text(value.toString()));
- }
- }
-
- public static class MyReducer extends MapReduceBase implements
- Reducer<LongWritable, Text, StudentinfoRecord, Text> {
- @Override
- public void reduce(LongWritable key, Iterator<Text> values,
- OutputCollector<StudentinfoRecord, Text> output, Reporter reporter) throws IOException {
- String[] splits = values.next().toString().split(" ");
- StudentinfoRecord r = new StudentinfoRecord();
- r.id = Integer.parseInt(splits[0]);
- r.name = splits[1];
- output.collect(r, new Text(r.name));
- }
- }
-
- public static void main(String[] args) throws IOException {
- JobConf conf = new JobConf(Mysql2Mr.class);
- DistributedCache.addFileToClassPath(new Path("/tmp/mysql-connector-java-5.0.8-bin.jar"), conf);
-
- conf.setMapOutputKeyClass(LongWritable.class);
- conf.setMapOutputValueClass(Text.class);
- conf.setOutputKeyClass(LongWritable.class);
- conf.setOutputValueClass(Text.class);
-
- conf.setOutputFormat(DBOutputFormat.class);
- conf.setInputFormat(DBInputFormat.class);
- // // mysql to hdfs
- // conf.setReducerClass(IdentityReducer.class);
- // Path outPath = new Path("/tmp/1");
- // FileSystem.get(conf).delete(outPath, true);
- // FileOutputFormat.setOutputPath(conf, outPath);
-
- DBConfiguration.configureDB(conf, "com.mysql.jdbc.Driver", "jdbc:mysql://192.168.1.101:3306/test",
- "root", "root");
- String[] fields = { "id", "name" };
- // 从 t 表读数据
- DBInputFormat.setInput(conf, StudentinfoRecord.class, "t", null, "id", fields);
- // mapreduce 将数据输出到 t2 表
- DBOutputFormat.setOutput(conf, "t2", "id", "name");
- // conf.setMapperClass(org.apache.hadoop.mapred.lib.IdentityMapper.class);
- conf.setMapperClass(DBInputMapper.class);
- conf.setReducerClass(MyReducer.class);
-
- JobClient.runJob(conf);
- }
- }
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6、结果:
执行两次后,你可以看到mysql结果:
- mysql> select * from t2;
- +------+-------+
- | id | name |
- +------+-------+
- | 1 | june |
- | 2 | decli |
- | 3 | hello |
- | 4 | june |
- | 5 | decli |
- | 6 | hello |
- | 7 | june |
- | 8 | decli |
- | 9 | hello |
- | 10 | june |
- | 11 | june |
- | 12 | decli |
- | 13 | hello |
- | 1 | june |
- | 2 | decli |
- | 3 | hello |
- | 4 | june |
- | 5 | decli |
- | 6 | hello |
- | 7 | june |
- | 8 | decli |
- | 9 | hello |
- | 10 | june |
- | 11 | june |
- | 12 | decli |
- | 13 | hello |
- +------+-------+
- 26 rows in set (0.00 sec)
-
- mysql>
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7、日志:
- 13/07/29 02:33:03 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
- 13/07/29 02:33:03 INFO filecache.TrackerDistributedCacheManager: Creating mysql-connector-java-5.0.8-bin.jar in /tmp/hadoop-june/mapred/local/archive/-8943686319031389138_-1232673160_640840668/192.168.1.101/tmp-work--8372797484204470322 with rwxr-xr-x
- 13/07/29 02:33:03 INFO filecache.TrackerDistributedCacheManager: Cached hdfs://192.168.1.101:9000/tmp/mysql-connector-java-5.0.8-bin.jar as /tmp/hadoop-june/mapred/local/archive/-8943686319031389138_-1232673160_640840668/192.168.1.101/tmp/mysql-connector-java-5.0.8-bin.jar
- 13/07/29 02:33:03 INFO filecache.TrackerDistributedCacheManager: Cached hdfs://192.168.1.101:9000/tmp/mysql-connector-java-5.0.8-bin.jar as /tmp/hadoop-june/mapred/local/archive/-8943686319031389138_-1232673160_640840668/192.168.1.101/tmp/mysql-connector-java-5.0.8-bin.jar
- 13/07/29 02:33:03 INFO mapred.JobClient: Running job: job_local_0001
- 13/07/29 02:33:03 INFO mapred.MapTask: numReduceTasks: 1
- 13/07/29 02:33:03 INFO mapred.MapTask: io.sort.mb = 100
- 13/07/29 02:33:03 INFO mapred.MapTask: data buffer = 79691776/99614720
- 13/07/29 02:33:03 INFO mapred.MapTask: record buffer = 262144/327680
- 13/07/29 02:33:03 INFO mapred.MapTask: Starting flush of map output
- 13/07/29 02:33:03 INFO mapred.MapTask: Finished spill 0
- 13/07/29 02:33:03 INFO mapred.Task: Task:attempt_local_0001_m_000000_0 is done. And is in the process of commiting
- 13/07/29 02:33:04 INFO mapred.JobClient: map 0% reduce 0%
- 13/07/29 02:33:06 INFO mapred.LocalJobRunner:
- 13/07/29 02:33:06 INFO mapred.Task: Task 'attempt_local_0001_m_000000_0' done.
- 13/07/29 02:33:06 INFO mapred.LocalJobRunner:
- 13/07/29 02:33:06 INFO mapred.Merger: Merging 1 sorted segments
- 13/07/29 02:33:06 INFO mapred.Merger: Down to the last merge-pass, with 1 segments left of total size: 235 bytes
- 13/07/29 02:33:06 INFO mapred.LocalJobRunner:
- 13/07/29 02:33:06 INFO mapred.Task: Task:attempt_local_0001_r_000000_0 is done. And is in the process of commiting
- 13/07/29 02:33:07 INFO mapred.JobClient: map 100% reduce 0%
- 13/07/29 02:33:09 INFO mapred.LocalJobRunner: reduce > reduce
- 13/07/29 02:33:09 INFO mapred.Task: Task 'attempt_local_0001_r_000000_0' done.
- 13/07/29 02:33:09 WARN mapred.FileOutputCommitter: Output path is null in cleanup
- 13/07/29 02:33:10 INFO mapred.JobClient: map 100% reduce 100%
- 13/07/29 02:33:10 INFO mapred.JobClient: Job complete: job_local_0001
- 13/07/29 02:33:10 INFO mapred.JobClient: Counters: 18
- 13/07/29 02:33:10 INFO mapred.JobClient: File Input Format Counters
- 13/07/29 02:33:10 INFO mapred.JobClient: Bytes Read=0
- 13/07/29 02:33:10 INFO mapred.JobClient: File Output Format Counters
- 13/07/29 02:33:10 INFO mapred.JobClient: Bytes Written=0
- 13/07/29 02:33:10 INFO mapred.JobClient: FileSystemCounters
- 13/07/29 02:33:10 INFO mapred.JobClient: FILE_BYTES_READ=1211691
- 13/07/29 02:33:10 INFO mapred.JobClient: HDFS_BYTES_READ=1081704
- 13/07/29 02:33:10 INFO mapred.JobClient: FILE_BYTES_WRITTEN=2392844
- 13/07/29 02:33:10 INFO mapred.JobClient: Map-Reduce Framework
- 13/07/29 02:33:10 INFO mapred.JobClient: Map output materialized bytes=239
- 13/07/29 02:33:10 INFO mapred.JobClient: Map input records=13
- 13/07/29 02:33:10 INFO mapred.JobClient: Reduce shuffle bytes=0
- 13/07/29 02:33:10 INFO mapred.JobClient: Spilled Records=26
- 13/07/29 02:33:10 INFO mapred.JobClient: Map output bytes=207
- 13/07/29 02:33:10 INFO mapred.JobClient: Map input bytes=13
- 13/07/29 02:33:10 INFO mapred.JobClient: SPLIT_RAW_BYTES=75
- 13/07/29 02:33:10 INFO mapred.JobClient: Combine input records=0
- 13/07/29 02:33:10 INFO mapred.JobClient: Reduce input records=13
- 13/07/29 02:33:10 INFO mapred.JobClient: Reduce input groups=13
- 13/07/29 02:33:10 INFO mapred.JobClient: Combine output records=0
- 13/07/29 02:33:10 INFO mapred.JobClient: Reduce output records=13
- 13/07/29 02:33:10 INFO mapred.JobClient: Map output records=13
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MapReduce直接连接Mysql获取数据
Mysql中数据:
- mysql> select * from lxw_tbls;
- +---------------------+----------------+
- | TBL_NAME | TBL_TYPE |
- +---------------------+----------------+
- | lxw_test_table | EXTERNAL_TABLE |
- | lxw_t | MANAGED_TABLE |
- | lxw_t1 | MANAGED_TABLE |
- | tt | MANAGED_TABLE |
- | tab_partition | MANAGED_TABLE |
- | lxw_hbase_table_1 | MANAGED_TABLE |
- | lxw_hbase_user_info | MANAGED_TABLE |
- | t | EXTERNAL_TABLE |
- | lxw_jobid | MANAGED_TABLE |
- +---------------------+----------------+
- 9 rows in set (0.01 sec)
-
- mysql> select * from lxw_tbls where TBL_NAME like 'lxw%' order by TBL_NAME;
- +---------------------+----------------+
- | TBL_NAME | TBL_TYPE |
- +---------------------+----------------+
- | lxw_hbase_table_1 | MANAGED_TABLE |
- | lxw_hbase_user_info | MANAGED_TABLE |
- | lxw_jobid | MANAGED_TABLE |
- | lxw_t | MANAGED_TABLE |
- | lxw_t1 | MANAGED_TABLE |
- | lxw_test_table | EXTERNAL_TABLE |
- +---------------------+----------------+
- 6 rows in set (0.00 sec)
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MapReduce程序代码,ConnMysql.java:
- package com.lxw.study;
-
- import java.io.DataInput;
- import java.io.DataOutput;
- import java.io.IOException;
- import java.net.URI;
- import java.sql.PreparedStatement;
- import java.sql.ResultSet;
- import java.sql.SQLException;
- import java.util.Iterator;
-
- import org.apache.hadoop.conf.Configuration;
- import org.apache.hadoop.filecache.DistributedCache;
- import org.apache.hadoop.fs.FileSystem;
- import org.apache.hadoop.fs.Path;
- import org.apache.hadoop.io.LongWritable;
- import org.apache.hadoop.io.Text;
- import org.apache.hadoop.io.Writable;
- import org.apache.hadoop.mapreduce.Job;
- import org.apache.hadoop.mapreduce.Mapper;
- import org.apache.hadoop.mapreduce.Reducer;
- import org.apache.hadoop.mapreduce.lib.db.DBConfiguration;
- import org.apache.hadoop.mapreduce.lib.db.DBInputFormat;
- import org.apache.hadoop.mapreduce.lib.db.DBWritable;
- import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
-
- public class ConnMysql {
-
- private static Configuration conf = new Configuration();
-
- static {
- conf.addResource(new Path("F:/lxw-hadoop/hdfs-site.xml"));
- conf.addResource(new Path("F:/lxw-hadoop/mapred-site.xml"));
- conf.addResource(new Path("F:/lxw-hadoop/core-site.xml"));
- conf.set("mapred.job.tracker", "10.133.103.21:50021");
- }
-
- public static class TblsRecord implements Writable, DBWritable {
- String tbl_name;
- String tbl_type;
-
- public TblsRecord() {
-
- }
-
- @Override
- public void write(PreparedStatement statement) throws SQLException {
- // TODO Auto-generated method stub
- statement.setString(1, this.tbl_name);
- statement.setString(2, this.tbl_type);
- }
-
- @Override
- public void readFields(ResultSet resultSet) throws SQLException {
- // TODO Auto-generated method stub
- this.tbl_name = resultSet.getString(1);
- this.tbl_type = resultSet.getString(2);
- }
-
- @Override
- public void write(DataOutput out) throws IOException {
- // TODO Auto-generated method stub
- Text.writeString(out, this.tbl_name);
- Text.writeString(out, this.tbl_type);
- }
-
- @Override
- public void readFields(DataInput in) throws IOException {
- // TODO Auto-generated method stub
- this.tbl_name = Text.readString(in);
- this.tbl_type = Text.readString(in);
- }
-
- public String toString() {
- return new String(this.tbl_name + " " + this.tbl_type);
- }
-
- }
-
- public static class ConnMysqlMapper extends Mapper<LongWritable,TblsRecord,Text,Text> {
- public void map(LongWritable key,TblsRecord values,Context context)
- throws IOException,InterruptedException {
- context.write(new Text(values.tbl_name), new Text(values.tbl_type));
- }
- }
-
- public static class ConnMysqlReducer extends Reducer<Text,Text,Text,Text> {
- public void reduce(Text key,Iterable<Text> values,Context context)
- throws IOException,InterruptedException {
- for(Iterator<Text> itr = values.iterator();itr.hasNext();) {
- context.write(key, itr.next());
- }
- }
- }
-
- public static void main(String[] args) throws Exception {
- Path output = new Path("/user/lxw/output/");
-
- FileSystem fs = FileSystem.get(URI.create(output.toString()), conf);
- if (fs.exists(output)) {
- fs.delete(output);
- }
-
- //mysql的jdbc驱动
- DistributedCache.addFileToClassPath(new Path(
- "hdfs://hd022-test.nh.sdo.com/user/liuxiaowen/mysql-connector-java-5.1.13-bin.jar"), conf);
-
- DBConfiguration.configureDB(conf, "com.mysql.jdbc.Driver",
- "jdbc:mysql://10.133.103.22:3306/hive", "hive", "hive");
-
- Job job = new Job(conf,"test mysql connection");
- job.setJarByClass(ConnMysql.class);
-
- job.setMapperClass(ConnMysqlMapper.class);
- job.setReducerClass(ConnMysqlReducer.class);
-
- job.setOutputKeyClass(Text.class);
- job.setOutputValueClass(Text.class);
-
- job.setInputFormatClass(DBInputFormat.class);
- FileOutputFormat.setOutputPath(job, output);
-
- //列名
- String[] fields = { "TBL_NAME", "TBL_TYPE" };
- //六个参数分别为:
- //1.Job;2.Class<? extends DBWritable>
- //3.表名;4.where条件
- //5.order by语句;6.列名
- DBInputFormat.setInput(job, TblsRecord.class,
- "lxw_tbls", "TBL_NAME like 'lxw%'", "TBL_NAME", fields);
-
- System.exit(job.waitForCompletion(true) ? 0 : 1);
- }
-
- }
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运行结果:
- [lxw@hd025-test ~]$ hadoop fs -cat /user/lxw/output/part-r-00000
- lxw_hbase_table_1 MANAGED_TABLE
- lxw_hbase_user_info MANAGED_TABLE
- lxw_jobid MANAGED_TABLE
- lxw_t MANAGED_TABLE
- lxw_t1 MANAGED_TABLE
- lxw_test_table EXTERNAL_TABLE
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http://www.aboutyun.com/forum.php?highlight=MapReduce+MySQL&mod=viewthread&tid=7405