我在Python中创建了一个简单的map reduce，只是为了测试os.environ['mapreduce_map_input_file']调用，如下所示：
地图.py
#!/usr/bin/python
import sys
# input comes from STDIN (stream data that goes to the program)
for line in sys.stdin:
l = line.strip().split()
for word in l:
# output goes to STDOUT (stream data that the program writes)
print "%st%d" %( word, 1 )
减少.py
#!/usr/bin/python
import sys
import os
current_word = None
current_sum = 0
# input comes from STDIN (stream data that goes to the program)
for line in sys.stdin:
word, count = line.strip().split("t", 1)
try:
count = int(count)
except ValueError:
continue
if word == current_word:
current_sum += count
else:
if current_word:
# output goes to STDOUT (stream data that the program writes)
print "%st%d" %( current_word, current_sum )
print (os.environ['mapreduce_map_input_file'])
current_word = word
current_sum = count
错误消息：
Traceback (most recent call last):
File "/Users/brunomacedo/Desktop/Big-Data/./reduce.py", line 25, in <module>
print (os.environ['mapreduce_map_input_file'])
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/UserDict.py", line 23, in __getitem__
raise KeyError(key)
KeyError: 'mapreduce_map_input_file'
15/03/06 17:50:26 INFO streaming.PipeMapRed: Records R/W=16127/1
15/03/06 17:50:26 INFO streaming.PipeMapRed: MRErrorThread done
15/03/06 17:50:26 WARN streaming.PipeMapRed: java.io.IOException: Stream closed
15/03/06 17:50:26 INFO streaming.PipeMapRed: PipeMapRed failed!
java.lang.RuntimeException: PipeMapRed.waitOutputThreads(): subprocess failed with code 1
at org.apache.hadoop.streaming.PipeMapRed.waitOutputThreads(PipeMapRed.java:322)
at org.apache.hadoop.streaming.PipeMapRed.mapRedFinished(PipeMapRed.java:535)
at org.apache.hadoop.streaming.PipeReducer.reduce(PipeReducer.java:128)
at org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:444)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:392)
at org.apache.hadoop.mapred.LocalJobRunner$Job$ReduceTaskRunnable.run(LocalJobRunner.java:319)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
15/03/06 17:50:26 WARN streaming.PipeMapRed: java.io.IOException: Stream closed
15/03/06 17:50:26 INFO streaming.PipeMapRed: PipeMapRed failed!
java.lang.RuntimeException: PipeMapRed.waitOutputThreads(): subprocess failed with code 1
at org.apache.hadoop.streaming.PipeMapRed.waitOutputThreads(PipeMapRed.java:322)
at org.apache.hadoop.streaming.PipeMapRed.mapRedFinished(PipeMapRed.java:535)
at org.apache.hadoop.streaming.PipeReducer.close(PipeReducer.java:134)
at org.apache.hadoop.io.IOUtils.cleanup(IOUtils.java:237)
at org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:459)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:392)
at org.apache.hadoop.mapred.LocalJobRunner$Job$ReduceTaskRunnable.run(LocalJobRunner.java:319)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
15/03/06 17:50:26 INFO mapred.LocalJobRunner: reduce task executor complete.
15/03/06 17:50:26 WARN mapred.LocalJobRunner: job_local1265836882_0001
java.lang.Exception: java.lang.RuntimeException: PipeMapRed.waitOutputThreads(): subprocess failed with code 1
at org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462)
at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:529)
Caused by: java.lang.RuntimeException: PipeMapRed.waitOutputThreads(): subprocess failed with code 1
at org.apache.hadoop.streaming.PipeMapRed.waitOutputThreads(PipeMapRed.java:322)
at org.apache.hadoop.streaming.PipeMapRed.mapRedFinished(PipeMapRed.java:535)
at org.apache.hadoop.streaming.PipeReducer.close(PipeReducer.java:134)
at org.apache.hadoop.io.IOUtils.cleanup(IOUtils.java:237)
at org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:459)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:392)
at org.apache.hadoop.mapred.LocalJobRunner$Job$ReduceTaskRunnable.run(LocalJobRunner.java:319)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
15/03/06 17:50:27 INFO mapreduce.Job: Job job_local1265836882_0001 failed with state FAILED due to: NA
15/03/06 17:50:27 INFO mapreduce.Job: Counters: 35
File System Counters
FILE: Number of bytes read=181735210
FILE: Number of bytes written=292351104
FILE: Number of read operations=0
FILE: Number of large read operations=0
FILE: Number of write operations=0
HDFS: Number of bytes read=0
HDFS: Number of bytes written=0
HDFS: Number of read operations=0
HDFS: Number of large read operations=0
HDFS: Number of write operations=0
Map-Reduce Framework
Map input records=100
Map output records=334328
Map output bytes=2758691
Map output materialized bytes=3427947
Input split bytes=14100
Combine input records=0
Combine output records=0
Reduce input groups=0
Reduce shuffle bytes=3427947
Reduce input records=0
Reduce output records=0
Spilled Records=334328
Shuffled Maps =100
Failed Shuffles=0
Merged Map outputs=100
GC time elapsed (ms)=1224
Total committed heap usage (bytes)=49956257792
Shuffle Errors
BAD_ID=0
CONNECTION=0
IO_ERROR=0
WRONG_LENGTH=0
WRONG_MAP=0
WRONG_REDUCE=0
File Input Format Counters
Bytes Read=2090035
File Output Format Counters
Bytes Written=0
15/03/06 17:50:27 ERROR streaming.StreamJob: Job not successful!
Streaming Command Failed!
我用来运行它的命令：
hadoop jar /usr/local/Cellar/hadoop/2.6.0/libexec/share/hadoop/tools/lib/hadoop-streaming-2.6.0.jar
-D mapreduce.job.reduces=1
-file map.py
-mapper map.py
-file reduce.py
-reducer reduce.py
-input file:///Users/brunomacedo/Desktop/Big-Data/articles
-output file:///Users/brunomacedo/Desktop/Big-Data/output
如果我去掉print (os.environ['mapreduce_map_input_file'])这条线，它就能完美地工作。此行的目的是打印字数来源的输入文件的名称。无论如何，我这样做只是为了测试这个命令，因为我需要在更复杂的项目中使用它。
有人能帮我这个电话怎么了吗？非常感谢！
编辑：
我使用的是Hadoop2.6.0
当我在reduce文件中调用os.environ['mapreduce_map_input_file']或os.environ['map_input_file']时，它不起作用。但它在map文件中有效。这是有道理的，因为reducer无法知道mapper输出来自哪个输入文件（除非您直接从mapper发送该信息）。
我无法直接运行os.environ['mapreduce_map_input_file']或os.environ['map_input_file']。但在映射器中使用这个似乎一直有效：
try:
input_file = os.environ['mapreduce_map_input_file']
except KeyError:
input_file = os.environ['map_input_file']