Hadoop Streaming原理及实践

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Hadoop Streaming原理及实践

shiyanjuncn 2016-04-14 10:37:51 浏览1628
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Hadoop Streaming提供了一个便于进行MapReduce编程的工具包,使用它可以基于一些可执行命令、脚本语言或其他编程语言来实现Mapper和 Reducer,从而充分利用Hadoop并行计算框架的优势和能力,来处理大数据。需要注意的是,Streaming方式是基于Unix系统的标准输入输出来进行MapReduce Job的运行,它区别与Pipes的地方主要是通信协议,Pipes使用的是Socket通信,是对使用C++语言来实现MapReduce Job并通过Socket通信来与Hadopp平台通信,完成Job的执行。任何支持标准输入输出特性的编程语言都可以使用Streaming方式来实现MapReduce Job,基本原理就是输入从Unix系统标准输入,输出使用Unix系统的标准输出。
Hadoop是使用Java语言编写的,所以最直接的方式的就是使用Java语言来实现Mapper和Reducer,然后配置MapReduce Job,提交到集群计算环境来完成计算。但是很多开发者可能对Java并不熟悉,而是对一些具有脚本特性的语言,如C++、Shell、Python、 Ruby、PHP、Perl有实际开发经验,Hadoop Streaming为这一类开发者提供了使用Hadoop集群来进行处理数据的工具,即工具包hadoop-streaming-.jar。
Hadoop Streaming使用了Unix的标准输入输出作为Hadoop和其他编程语言的开发接口,因此在其他的编程语言所写的程序中,只需要将标准输入作为程 序的输入,将标准输出作为程序的输出就可以了。在标准的输入输出中,Key和Value是以Tab作为分隔符,并且在Reducer的标准输入中,Hadoop框架保证了输入的数据是经过了按Key排序的。
如何使用Hadoop Streaming工具呢?我们可以查看该工具的使用方法,通过命令行来获取,如下所示:

01 xiaoxiang@ubuntu3:~/hadoop$ bin/hadoop jar ./contrib/streaming/hadoop-streaming-1.0.3.jar -info
02 Usage: $HADOOP_HOME/bin/hadoop jar $HADOOP_HOME/hadoop-streaming.jar [options]
03 Options:
04 -input <path> DFS input file(s) for the Map step
05 -output <path> DFS output directory for the Reduce step
06 -mapper <cmd|JavaClassName> The streaming command to run
07 -combiner <cmd|JavaClassName> The streaming command to run
08 -reducer <cmd|JavaClassName> The streaming command to run
09 -file <file> File/dir to be shipped in the Job jar file
10 -inputformat TextInputFormat(default)|SequenceFileAsTextInputFormat|JavaClassName Optional.
11 -outputformat TextOutputFormat(default)|JavaClassName Optional.
12 -partitioner JavaClassName Optional.
13 -numReduceTasks <num> Optional.
14 -inputreader <spec> Optional.
15 -cmdenv <n>=<v> Optional. Pass env.var to streaming commands
16 -mapdebug <path> Optional. To run this script when a map task fails
17 -reducedebug <path> Optional. To run this script when a reduce task fails
18 -io <identifier> Optional.
19 -verbose
20
21 Generic options supported are
22 -conf <configuration file> specify an application configuration file
23 -D <property=value> use value for given property
24 -fs <local|namenode:port> specify a namenode
25 -jt <local|jobtracker:port> specify a job tracker
26 -files <comma separated list of files> specify comma separated files to be copied to the map reduce cluster
27 -libjars <comma separated list of jars> specify comma separated jar files to include in the classpath.
28 -archives <comma separated list of archives> specify comma separated archives to be unarchived on the compute machines.
29
30 The general command line syntax is
31 bin/hadoop command [genericOptions] [commandOptions]
32
33
34 In -input: globbing on <path> is supported and can have multiple -input
35 Default Map input format: a line is a record in UTF-8
36 the key part ends at first TAB, the rest of the line is the value
37 Custom input format: -inputformat package.MyInputFormat
38 Map output format, reduce input/output format:
39 Format defined by what the mapper command outputs. Line-oriented
40
41 The files named in the -file argument[s] end up in the
42 working directory when the mapper and reducer are run.
43 The location of this working directory is unspecified.
44
45 To set the number of reduce tasks (num. of output files):
46 -D mapred.reduce.tasks=10
47 To skip the sort/combine/shuffle/sort/reduce step:
48 Use -numReduceTasks 0
49 A Task's Map output then becomes a 'side-effect output' rather than a reduce input
50 This speeds up processing, This also feels more like "in-place" processing
51 because the input filename and the map input order are preserved
52 This equivalent -reducer NONE
53
54 To speed up the last maps:
55 -D mapred.map.tasks.speculative.execution=true
56 To speed up the last reduces:
57 -D mapred.reduce.tasks.speculative.execution=true
58 To name the job (appears in the JobTracker Web UI):
59 -D mapred.job.name='My Job'
60 To change the local temp directory:
61 -D dfs.data.dir=/tmp/dfs
62 -D stream.tmpdir=/tmp/streaming
63 Additional local temp directories with -cluster local:
64 -D mapred.local.dir=/tmp/local
65 -D mapred.system.dir=/tmp/system
66 -D mapred.temp.dir=/tmp/temp
67 To treat tasks with non-zero exit status as SUCCEDED:
68 -D stream.non.zero.exit.is.failure=false
69 Use a custom hadoopStreaming build along a standard hadoop install:
70 $HADOOP_HOME/bin/hadoop jar /path/my-hadoop-streaming.jar [...]\
71 [...] -D stream.shipped.hadoopstreaming=/path/my-hadoop-streaming.jar
72 For more details about jobconf parameters see:
73
74 http://wiki.apache.org/hadoop/JobConfFile
75
76 To set an environement variable in a streaming command:
77 -cmdenv EXAMPLE_DIR=/home/example/dictionaries/
78
79 Shortcut:
80 setenv HSTREAMING "$HADOOP_HOME/bin/hadoop jar $HADOOP_HOME/hadoop-streaming.jar"
81
82 Example: $HSTREAMING -mapper "/usr/local/bin/perl5 filter.pl"
83 -file /local/filter.pl -input "/logs/0604*/*" [...]
84 Ships a script, invokes the non-shipped perl interpreter
85 Shipped files go to the working directory so filter.pl is found by perl
86 Input files are all the daily logs for days in month 2006-04

面,我们分别选择几个可以使用Hadoop Streaming工具来进行计算的例子,比如对单词词频进行统计计算,即WordCount功能。
首先,我们准备测试使用的数据集,如下所示:

1 xiaoxiang@ubuntu3:~/hadoop$ bin/hadoop fs -lsr /user/xiaoxiang/dataset/join/
2 -rw-r--r-- 3 xiaoxiang supergroup 391103029 2013-03-26 12:19 /user/xiaoxiang/dataset/join/irc_basic_info.ds
3 -rw-r--r-- 3 xiaoxiang supergroup 11577164 2013-03-26 12:20 /user/xiaoxiang/dataset/join/irc_net_block.ds
4 -rw-r--r-- 3 xiaoxiang supergroup 8335235 2013-03-26 12:20 /user/xiaoxiang/dataset/join/irc_org_info.ds

一共有3个数据文件,大概将近400M大小。
下面,选择Python语言来实现MapReduce Job的运行。
使用Python实现Mapper,代码文件为word_count_mapper.py,代码如下所示:

1 #!/usr/bin/env python
2
3 import sys
4
5 for line in sys.stdin:
6 line = line.strip()
7 words = filter(lambda word: word, line.split())
8 for word in words:
9 print '%s\t%s' % (word, 1)

使用Python实现Reducer,代码文件为word_count_reducer.py,代码如下所示:

01 #!/usr/bin/env python
02
03 import sys
04 from operator import itemgetter
05
06 wc_dict = {}
07
08 for line in sys.stdin:
09 line = line.strip()
10 word, count = line.split()
11 try:
12 count = int(count)
13 wc_dict[word] = wc_dict.get(word, 0) + count
14 except ValueError:
15 pass
16
17 sorted_dict = sorted(wc_dict.items(), key=itemgetter(0))
18 for word, count in sorted_dict:
19 print '%s\t%s' % (word, count)

运行Python实现的MapReduce程序,如下所示:

01 xiaoxiang@ubuntu3:~/hadoop$ bin/hadoop jar ./contrib/streaming/hadoop-streaming-1.0.3.jar -input /user/xiaoxiang/dataset/join/ -output /user/xiaoxiang/output/streaming/python -mapper word_count_mapper.py -reducer word_count_reducer.py -numReduceTasks 2 -file *.py
02 packageJobJar: [word_count_mapper.py, word_count_reducer.py, /opt/stone/cloud/storage/tmp/hadoop-xiaoxiang/hadoop-unjar4066863202997744310/] [] /tmp/streamjob2336302975421423718.jar tmpDir=null
03 13/04/18 17:50:17 INFO util.NativeCodeLoader: Loaded the native-hadoop library
04 13/04/18 17:50:17 WARN snappy.LoadSnappy: Snappy native library not loaded
05 13/04/18 17:50:17 INFO mapred.FileInputFormat: Total input paths to process : 3
06 13/04/18 17:50:17 INFO streaming.StreamJob: getLocalDirs(): [/opt/stone/cloud/storage/mapred/local]
07 13/04/18 17:50:17 INFO streaming.StreamJob: Running job: job_201303302227_0047
08 13/04/18 17:50:17 INFO streaming.StreamJob: To kill this job, run:
09 13/04/18 17:50:17 INFO streaming.StreamJob: /opt/stone/cloud/hadoop-1.0.3/libexec/../bin/hadoop job -Dmapred.job.tracker=hdfs://ubuntu3:9001/ -killjob_201303302227_0047
10 13/04/18 17:50:17 INFO streaming.StreamJob: Tracking URL:http://ubuntu3:50030/jobdetails.jsp?jobid=job_201303302227_0047
11 13/04/18 17:50:18 INFO streaming.StreamJob: map 0% reduce 0%
12 13/04/18 17:50:33 INFO streaming.StreamJob: map 7% reduce 0%
13 13/04/18 17:50:36 INFO streaming.StreamJob: map 11% reduce 0%
14 13/04/18 17:50:39 INFO streaming.StreamJob: map 15% reduce 0%
15 13/04/18 17:50:42 INFO streaming.StreamJob: map 19% reduce 0%
16 13/04/18 17:50:45 INFO streaming.StreamJob: map 23% reduce 0%
17 13/04/18 17:50:48 INFO streaming.StreamJob: map 25% reduce 0%
18 13/04/18 17:51:09 INFO streaming.StreamJob: map 32% reduce 2%
19 13/04/18 17:51:12 INFO streaming.StreamJob: map 36% reduce 4%
20 13/04/18 17:51:15 INFO streaming.StreamJob: map 40% reduce 8%
21 13/04/18 17:51:18 INFO streaming.StreamJob: map 44% reduce 8%
22 13/04/18 17:51:21 INFO streaming.StreamJob: map 47% reduce 8%
23 13/04/18 17:51:24 INFO streaming.StreamJob: map 50% reduce 8%
24 13/04/18 17:51:45 INFO streaming.StreamJob: map 54% reduce 10%
25 13/04/18 17:51:48 INFO streaming.StreamJob: map 60% reduce 15%
26 13/04/18 17:51:51 INFO streaming.StreamJob: map 65% reduce 17%
27 13/04/18 17:51:55 INFO streaming.StreamJob: map 66% reduce 17%
28 13/04/18 17:51:58 INFO streaming.StreamJob: map 68% reduce 17%
29 13/04/18 17:52:01 INFO streaming.StreamJob: map 72% reduce 17%
30 13/04/18 17:52:04 INFO streaming.StreamJob: map 75% reduce 17%
31 13/04/18 17:52:19 INFO streaming.StreamJob: map 75% reduce 19%
32 13/04/18 17:52:22 INFO streaming.StreamJob: map 87% reduce 21%
33 13/04/18 17:52:25 INFO streaming.StreamJob: map 100% reduce 23%
34 13/04/18 17:52:28 INFO streaming.StreamJob: map 100% reduce 27%
35 13/04/18 17:52:31 INFO streaming.StreamJob: map 100% reduce 29%
36 13/04/18 17:52:37 INFO streaming.StreamJob: map 100% reduce 49%
37 13/04/18 17:52:40 INFO streaming.StreamJob: map 100% reduce 69%
38 13/04/18 17:52:43 INFO streaming.StreamJob: map 100% reduce 72%
39 13/04/18 17:52:46 INFO streaming.StreamJob: map 100% reduce 74%
40 13/04/18 17:52:49 INFO streaming.StreamJob: map 100% reduce 76%
41 13/04/18 17:52:52 INFO streaming.StreamJob: map 100% reduce 78%
42 13/04/18 17:52:55 INFO streaming.StreamJob: map 100% reduce 79%
43 13/04/18 17:52:58 INFO streaming.StreamJob: map 100% reduce 81%
44 13/04/18 17:53:01 INFO streaming.StreamJob: map 100% reduce 84%
45 13/04/18 17:53:04 INFO streaming.StreamJob: map 100% reduce 87%
46 13/04/18 17:53:07 INFO streaming.StreamJob: map 100% reduce 90%
47 13/04/18 17:53:10 INFO streaming.StreamJob: map 100% reduce 93%
48 13/04/18 17:53:13 INFO streaming.StreamJob: map 100% reduce 96%
49 13/04/18 17:53:16 INFO streaming.StreamJob: map 100% reduce 98%
50 13/04/18 17:53:19 INFO streaming.StreamJob: map 100% reduce 99%
51 13/04/18 17:53:22 INFO streaming.StreamJob: map 100% reduce 100%
52 13/04/18 17:54:10 INFO streaming.StreamJob: Job complete: job_201303302227_0047
53 13/04/18 17:54:10 INFO streaming.StreamJob: Output: /user/xiaoxiang/output/streaming/python

验证结果,如下所示:

01 xiaoxiang@ubuntu3:~/hadoop$ bin/hadoop fs -lsr /user/xiaoxiang/output/streaming/python
02 -rw-r--r-- 3 xiaoxiang supergroup 0 2013-04-18 17:54 /user/xiaoxiang/output/streaming/python/_SUCCESS
03 drwxr-xr-x - xiaoxiang supergroup 0 2013-04-18 17:50 /user/xiaoxiang/output/streaming/python/_logs
04 drwxr-xr-x - xiaoxiang supergroup 0 2013-04-18 17:50 /user/xiaoxiang/output/streaming/python/_logs/history
05 -rw-r--r-- 3 xiaoxiang supergroup 37646 2013-04-18 17:50 /user/xiaoxiang/output/streaming/python/_logs/history/job_201303302227_0047_1366278617842_xiaoxiang_streamjob2336302975421423718.jar
06 -rw-r--r-- 3 xiaoxiang supergroup 21656 2013-04-18 17:50 /user/xiaoxiang/output/streaming/python/_logs/history/job_201303302227_0047_conf.xml
07 -rw-r--r-- 3 xiaoxiang supergroup 91367389 2013-04-18 17:52 /user/xiaoxiang/output/streaming/python/part-00000
08 -rw-r--r-- 3 xiaoxiang supergroup 91268074 2013-04-18 17:52 /user/xiaoxiang/output/streaming/python/part-00001
09 xiaoxiang@ubuntu3:~/hadoop$ bin/hadoop fs -cat/user/xiaoxiang/output/streaming/python/part-00000 | head -5
10 ! 2
11 # 36
12 #039 1
13 #1059) 1
14 #1098 1

相关问题

在使用Python实现MapReduce时,总是执行失败?
可以查看TaskTracker结点运行日志,可以看到,总是找不到对应的Python脚本文件,错误示例如下:

01 xiaoxiang@ubuntu1:/opt/stone/cloud/storage/logs/hadoop/userlogs/job_201303302227_0045/attempt_201303302227_0045_m_000001_0$cat stderr
02 java.io.IOException: Cannot run program"/user/xiaoxiang/streaming/python/word_count_mapper.py": java.io.IOException: error=2, No such file or directory
03 at java.lang.ProcessBuilder.start(ProcessBuilder.java:460)
04 at org.apache.hadoop.streaming.PipeMapRed.configure(PipeMapRed.java:214)
05 at org.apache.hadoop.streaming.PipeMapper.configure(PipeMapper.java:66)
06 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
07 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
08 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
09 at java.lang.reflect.Method.invoke(Method.java:597)
10 at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:88)
11 at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:64)
12 at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:117)
13 at org.apache.hadoop.mapred.MapRunner.configure(MapRunner.java:34)
14 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
15 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
16 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
17 at java.lang.reflect.Method.invoke(Method.java:597)
18 at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:88)
19 at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:64)
20 at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:117)
21 at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:432)
22 at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372)
23 at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
24 at java.security.AccessController.doPrivileged(Native Method)
25 at javax.security.auth.Subject.doAs(Subject.java:396)
26 at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1121)
27 at org.apache.hadoop.mapred.Child.main(Child.java:249)
28 Caused by: java.io.IOException: java.io.IOException: error=2, No such file or directory
29 at java.lang.UNIXProcess.<init>(UNIXProcess.java:148)
30 at java.lang.ProcessImpl.start(ProcessImpl.java:65)
31 at java.lang.ProcessBuilder.start(ProcessBuilder.java:453)
32 ... 24 more

可以使用Streaming的-file选项指定脚本文件加入到Job的Jar文件中,即使用上面运行的命令行中指定的“-file *.py”, 而实现的2个Python脚本文件就在当前运行Job的结点当前目录下。

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