[JAVA][DB]用MR(MapReduce)查询hbase数据(Mapper参数传递)－用到TableMapper和Scan


首先，可以设置scan的startRow, stopRow, filter等属性。于是两种方案：

1.设置scan的filter，然后执行mapper，再reducer成一份结果

2.不用filter过滤，将filter做的事传给mapper做

进行了测试，前者在执行较少量scan记录的时候效率较后者高，但是执行的scan数量多了，便容易导致超时无返回而退出的情况。而为了实现后者，学会了如何向mapper任务中传递参数，走了一点弯路。

最后的一点思考是，用后者效率仍然不高，即便可用前者时效率也不高，因为默认的tablemapper是将对一个region的scan任务放在了一个mapper里，而我一个region有2G多，而我查的数据只占七八个region。于是，想能不能不以region为单位算做mapper，如果不能改，那只有用MR直接操作HBase底层HDFS文件了，这个，…，待研究。

上代码（为了保密，将表名啊，列名列族名啊都改了一下，有改漏的，大家当做没看见啊，另：主要供大家参考下方法，即用mr来查询海量hbase数据，还有如何向mapper传参数）：

[java]
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package mapreduce.hbase;

import java.io.IOException;

import mapreduce.HDFS_File;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.filter.Filter;
import org.apache.hadoop.hbase.filter.FilterList;
import org.apache.hadoop.hbase.filter.SingleColumnValueFilter;
import org.apache.hadoop.hbase.filter.CompareFilter.CompareOp;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
import org.apache.hadoop.hbase.mapreduce.TableMapper;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper.Context;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

/**
* 用MR对HBase进行查找，给出Scan的条件诸如startkey endkey;以及filters用来过滤掉不符合条件的记录 LicenseTable
* 的 RowKey 201101010000000095\xE5\xAE\x81WDTLBZ
*
* @author Wallace
*
*/
@SuppressWarnings("unused")
public class MRSearchAuto {
private static final Log LOG = LogFactory.getLog(MRSearchAuto.class);

private static String TABLE_NAME = "tablename";
private static byte[] FAMILY_NAME = Bytes.toBytes("cfname");
private static byte[][] QUALIFIER_NAME = { Bytes.toBytes("col1"),
Bytes.toBytes("col2"), Bytes.toBytes("col3") };

public static class SearchMapper extends
TableMapper<ImmutableBytesWritable, Text> {
private int numOfFilter = 0;

private Text word = new Text();
String[] strConditionStrings = new String[]{"","",""}/* { "新C87310", "10", "2" } */;

/*
* private void init(Configuration conf) throws IOException,
* InterruptedException { strConditionStrings[0] =
* conf.get("search.license").trim(); strConditionStrings[1] =
* conf.get("search.carColor").trim(); strConditionStrings[2] =
* conf.get("search.direction").trim(); LOG.info("license: " +
* strConditionStrings[0]); }
*/
protected void setup(Context context) throws IOException,
InterruptedException {
strConditionStrings[0] = context.getConfiguration().get("search.license").trim();
strConditionStrings[1] = context.getConfiguration().get("search.color").trim();
strConditionStrings[2] = context.getConfiguration().get("search.direction").trim();
}

protected void map(ImmutableBytesWritable key, Result value,
Context context) throws InterruptedException, IOException {
String string = "";
String tempString;

/**/
for (int i = 0; i < 1; i++) {
// /在此map里进行filter的功能
tempString = Text.decode(value.getValue(FAMILY_NAME,
QUALIFIER_NAME[i]));
if (tempString.equals(/* strConditionStrings[i] */"新C87310")) {
LOG.info("新C87310. conf: " + strConditionStrings[0]);
if (tempString.equals(strConditionStrings[i])) {
string = string + tempString + " ";
} else {
return;
}
}

else {
return;
}
}

word.set(string);
context.write(null, word);
}
}

public void searchHBase(int numOfDays) throws IOException,
InterruptedException, ClassNotFoundException {
long startTime;
long endTime;

Configuration conf = HBaseConfiguration.create();
conf.set("hbase.zookeeper.quorum", "node2,node3,node4");
conf.set("fs.default.name", "hdfs://node1");
conf.set("mapred.job.tracker", "node1:54311");
/*
* 传递参数给map
*/
conf.set("search.license", "新C87310");
conf.set("search.color", "10");
conf.set("search.direction", "2");

Job job = new Job(conf, "MRSearchHBase");
System.out.println("search.license: " + conf.get("search.license"));
job.setNumReduceTasks(0);
job.setJarByClass(MRSearchAuto.class);
Scan scan = new Scan();
scan.addFamily(FAMILY_NAME);
byte[] startRow = Bytes.toBytes("2011010100000");
byte[] stopRow;
switch (numOfDays) {
case 1:
stopRow = Bytes.toBytes("2011010200000");
break;
case 10:
stopRow = Bytes.toBytes("2011011100000");
break;
case 30:
stopRow = Bytes.toBytes("2011020100000");
break;
case 365:
stopRow = Bytes.toBytes("2012010100000");
break;
default:
stopRow = Bytes.toBytes("2011010101000");
}
// 设置开始和结束key
scan.setStartRow(startRow);
scan.setStopRow(stopRow);

TableMapReduceUtil.initTableMapperJob(TABLE_NAME, scan,
SearchMapper.class, ImmutableBytesWritable.class, Text.class,
job);
Path outPath = new Path("searchresult");
HDFS_File file = new HDFS_File();
file.DelFile(conf, outPath.getName(), true); // 若已存在，则先删除
FileOutputFormat.setOutputPath(job, outPath);// 输出结果

startTime = System.currentTimeMillis();
job.waitForCompletion(true);
endTime = System.currentTimeMillis();
System.out.println("Time used: " + (endTime - startTime));
System.out.println("startRow:" + Text.decode(startRow));
System.out.println("stopRow: " + Text.decode(stopRow));
}

public static void main(String args[]) throws IOException,
InterruptedException, ClassNotFoundException {
MRSearchAuto mrSearchAuto = new MRSearchAuto();
int numOfDays = 1;
if (args.length == 1)
numOfDays = Integer.valueOf(args[0]);
System.out.println("Num of days: " + numOfDays);
mrSearchAuto.searchHBase(numOfDays);
}
}

package mapreduce.hbase;

import java.io.IOException;

import mapreduce.HDFS_File;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.filter.Filter;
import org.apache.hadoop.hbase.filter.FilterList;
import org.apache.hadoop.hbase.filter.SingleColumnValueFilter;
import org.apache.hadoop.hbase.filter.CompareFilter.CompareOp;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
import org.apache.hadoop.hbase.mapreduce.TableMapper;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper.Context;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

/**
* 用MR对HBase进行查找，给出Scan的条件诸如startkey endkey;以及filters用来过滤掉不符合条件的记录 LicenseTable
* 的 RowKey 201101010000000095\xE5\xAE\x81WDTLBZ
*
* @author Wallace
*
*/
@SuppressWarnings("unused")
public class MRSearchAuto {
private static final Log LOG = LogFactory.getLog(MRSearchAuto.class);

private static String TABLE_NAME = "tablename";
private static byte[] FAMILY_NAME = Bytes.toBytes("cfname");
private static byte[][] QUALIFIER_NAME = { Bytes.toBytes("col1"),
Bytes.toBytes("col2"), Bytes.toBytes("col3") };

public static class SearchMapper extends
TableMapper<ImmutableBytesWritable, Text> {
private int numOfFilter = 0;

private Text word = new Text();
String[] strConditionStrings = new String[]{"","",""}/* { "新C87310", "10", "2" } */;

/*
* private void init(Configuration conf) throws IOException,
* InterruptedException { strConditionStrings[0] =
* conf.get("search.license").trim(); strConditionStrings[1] =
* conf.get("search.carColor").trim(); strConditionStrings[2] =
* conf.get("search.direction").trim(); LOG.info("license: " +
* strConditionStrings[0]); }
*/
protected void setup(Context context) throws IOException,
InterruptedException {
strConditionStrings[0] = context.getConfiguration().get("search.license").trim();
strConditionStrings[1] = context.getConfiguration().get("search.color").trim();
strConditionStrings[2] = context.getConfiguration().get("search.direction").trim();
}

protected void map(ImmutableBytesWritable key, Result value,
Context context) throws InterruptedException, IOException {
String string = "";
String tempString;

/**/
for (int i = 0; i < 1; i++) {
// /在此map里进行filter的功能
tempString = Text.decode(value.getValue(FAMILY_NAME,
QUALIFIER_NAME[i]));
if (tempString.equals(/* strConditionStrings[i] */"新C87310")) {
LOG.info("新C87310. conf: " + strConditionStrings[0]);
if (tempString.equals(strConditionStrings[i])) {
string = string + tempString + " ";
} else {
return;
}
}

else {
return;
}
}

word.set(string);
context.write(null, word);
}
}

public void searchHBase(int numOfDays) throws IOException,
InterruptedException, ClassNotFoundException {
long startTime;
long endTime;

Configuration conf = HBaseConfiguration.create();
conf.set("hbase.zookeeper.quorum", "node2,node3,node4");
conf.set("fs.default.name", "hdfs://node1");
conf.set("mapred.job.tracker", "node1:54311");
/*
* 传递参数给map
*/
conf.set("search.license", "新C87310");
conf.set("search.color", "10");
conf.set("search.direction", "2");

Job job = new Job(conf, "MRSearchHBase");
System.out.println("search.license: " + conf.get("search.license"));
job.setNumReduceTasks(0);
job.setJarByClass(MRSearchAuto.class);
Scan scan = new Scan();
scan.addFamily(FAMILY_NAME);
byte[] startRow = Bytes.toBytes("2011010100000");
byte[] stopRow;
switch (numOfDays) {
case 1:
stopRow = Bytes.toBytes("2011010200000");
break;
case 10:
stopRow = Bytes.toBytes("2011011100000");
break;
case 30:
stopRow = Bytes.toBytes("2011020100000");
break;
case 365:
stopRow = Bytes.toBytes("2012010100000");
break;
default:
stopRow = Bytes.toBytes("2011010101000");
}
// 设置开始和结束key
scan.setStartRow(startRow);
scan.setStopRow(stopRow);

TableMapReduceUtil.initTableMapperJob(TABLE_NAME, scan,
SearchMapper.class, ImmutableBytesWritable.class, Text.class,
job);
Path outPath = new Path("searchresult");
HDFS_File file = new HDFS_File();
file.DelFile(conf, outPath.getName(), true); // 若已存在，则先删除
FileOutputFormat.setOutputPath(job, outPath);// 输出结果

startTime = System.currentTimeMillis();
job.waitForCompletion(true);
endTime = System.currentTimeMillis();
System.out.println("Time used: " + (endTime - startTime));
System.out.println("startRow:" + Text.decode(startRow));
System.out.println("stopRow: " + Text.decode(stopRow));
}

public static void main(String args[]) throws IOException,
InterruptedException, ClassNotFoundException {
MRSearchAuto mrSearchAuto = new MRSearchAuto();
int numOfDays = 1;
if (args.length == 1)
numOfDays = Integer.valueOf(args[0]);
System.out.println("Num of days: " + numOfDays);
mrSearchAuto.searchHBase(numOfDays);
}
}

开始时，我是在外面conf.set了传入的参数，而在mapper的init(Configuration)里get参数并赋给mapper对象。

将参数传给map运行时结果不对

for (int i = 0; i < 1; i++) {

// /在此map里进行filter的功能

tempString = Text.decode(value.getValue(FAMILY_NAME,

QUALIFIER_NAME[i]));

if (tempString.equals(/*strConditionStrings[i]*/"新C87310"))

string = string + tempString + " ";

else {

return;

}

}

如果用下面的mapper的init获取conf传来的参数，然后在上面map函数里进行调用，结果便不对了。

直接指定值时和参数传过来相同的值时，其output的结果分别为1条和0条。

private void init(Configuration conf) throws IOException,

InterruptedException {

strConditionStrings[0] = conf.get("search.licenseNumber").trim();

strConditionStrings[1] = conf.get("search.carColor").trim();

strConditionStrings[2] = conf.get("search.direction").trim();

}

加了个日志写

private static final Log LOG = LogFactory.getLog(MRSearchAuto.class);

init()函数里：

LOG.info("license: " + strConditionStrings[0]);

map里

if (tempString.equals(/* strConditionStrings[i] */"新C87310")) {

LOG.info("新C87310. conf: " + strConditionStrings[0]);

然后在网页 namenode:50030上看任务，最终定位到哪台机器执行了那个map，然后看日志

mapreduce.hbase.TestMRHBase: 新C87310. conf: null

在conf.set之后我也写了下，那时正常，但是在map里却是null了，而在map类的init函数打印的却没有打印。

因此，问题应该是：

map类的init()函数没有执行到！

于是init()的获取conf中参数值并赋给map里变量的操作便未执行，同时打印日志也未执行。

OK！看怎么解决

放在setup里获取

protected void setup(Context context) throws IOException,

InterruptedException {

// strConditionStrings[0] = context.getConfiguration().get("search.license").trim();

// strConditionStrings[1] = context.getConfiguration().get("search.color").trim();

// strConditionStrings[2] = context.getConfiguration().get("search.direction").trim();

}

报错

12/01/12 11:21:56 INFO mapred.JobClient: map 0% reduce 0%

12/01/12 11:22:03 INFO mapred.JobClient: Task Id : attempt_201201100941_0071_m_000000_0, Status : FAILED

java.lang.NullPointerException

at mapreduce.hbase.MRSearchAuto$SearchMapper.setup(MRSearchAuto.java:66)

at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:142)

at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:656)

at org.apache.hadoop.mapred.MapTask.run(MapTask.java:325)

at org.apache.hadoop.mapred.Child$4.run(Child.java:270)

at java.security.AccessController.doPrivileged(Native Method)

at javax.security.auth.Subject.doAs(Subject.java:396)

at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1127)

at org.apache.hadoop.mapred.Child.main(Child.java:264)

attempt_201201100941_0071_m_000000_0: log4j:WARN No appenders could be found for logger (org.apache.hadoop.hdfs.DFSClient).

attempt_201201100941_0071_m_000000_0: log4j:WARN Please initialize the log4j system properly.

12/01/12 11:22:09 INFO mapred.JobClient: Task Id : attempt_201201100941_0071_m_000000_1, Status : FAILED

java.lang.NullPointerException

at mapreduce.hbase.MRSearchAuto$SearchMapper.setup(MRSearchAuto.java:66)

at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:142)

at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:656)

at org.apache.hadoop.mapred.MapTask.run(MapTask.java:325)

at org.apache.hadoop.mapred.Child$4.run(Child.java:270)

at java.security.AccessController.doPrivileged(Native Method)

at javax.security.auth.Subject.doAs(Subject.java:396)

at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1127)

at org.apache.hadoop.mapred.Child.main(Child.java:264)

然后将setup里的东西注释掉，无错，错误应该在context上，进一步确认，在里面不用context，直接赋值，有结果，好！

说明是context的事了，NullPointerException,应该是context.getConfiguration().get("search.license")这些中有一个是null的。

突然想起来，改了下get时候的属性，而set时候没改，于是不对应，于是context.getConfiguration().get("search.color")及下面的一项都是null，null.trim()报的异常。

conf.set("search.license", "新C87310");

conf.set("search.color", "10");

conf.set("search.direction", "2");

修改后，问题解决。

实现了向map中传参数

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原帖：/article/8666365.html

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