python - Hadoop MapReduce Wordcount python执行错误

Question

我正在尝试执行一个 python MapReduce wordcount 程序

我取自 writing a Hadoop MapReduce program in python 只是想了解它是如何工作的，但问题始终是工作不成功!

我在 Cloudera VM 中使用这个库执行 mapper.py 和 reducer.py

/usr/lib/hadoop-0.20-mapreduce/contrib/streaming/hadoop-streaming-2.6.0-mr1-cdh5.12.0.jar

执行命令:

hadoop jar /usr/lib/hadoop-0.20-mapreduce/contrib/streaming/hadoop-streaming-2.6.0-mr1-cdh5.12.0.jar
-Dmaperd.reduce, tasks=1
-file wordcount/mapper.py 
-mapper mapper.py -file wordcount/reducer.py
-reducer reducer.py
-input myinput/test.txt
-output output

Answer 1

问题出在文件mapper.py和reducer.py必须来自本地的路径上

但输入文件必须来自hdfs路径

首先，必须在本地使用测试python代码

cat <input file> | python <path from>/mapper.py | python <path from local>/reducer.py

然后在hdfs上

hadoop jar /usr/lib/hadoop-0.20-mapreduce/contrib/streaming/hadoop-streaming-2.6.0-mr1-cdh5.12.0.jar 

-Dmaperd.reduce,tasks=1 -file <path of local>/mapper.py 

-mapper "python <path from local>/mapper.py" 

-file <path from local>/reducer.py -

reducer "python <path of local>/reducer.py" 

-input <path from hdfs>/myinput/test.txt 

-output output