Python 如何使用Hadoop流在本地Hadoop集群中运行MRJob？

我目前正在学习一门大数据课程，我的一个项目是在本地设置的Hadoop集群上运行我的Mapper/Reducer

我一直在使用Python和类的MRJob库

下面是我目前为Mapper/Reducer编写的Python代码

from mrjob.job import MRJob
from mrjob.step import MRStep
import re
import os

WORD_RE = re.compile(r"[\w']+")
choice = ""

class MRPrepositionsFinder(MRJob):

def steps(self):
    return [
        MRStep(mapper=self.mapper_get_words),
        MRStep(reducer=self.reducer_find_prep_word)
    ]

def mapper_get_words(self, _, line):
    # set word_list to indicators, convert to lowercase, and strip whitespace
    word_list = set(line.lower().strip() for line in open("/hdfs/user/user/indicators.txt"))

    # set filename to map_input_file
    fileName = os.environ['map_input_file']
    # itterate through each word in line
    for word in WORD_RE.findall(line):
        # if word is in indicators, yield chocie as filename
        if word.lower() in word_list:
            choice = fileName.split('/')[5]
            yield (choice, 1)

def reducer_find_prep_word(self, choice, counts):
    # each item of choice is (choice, count),
    # so yielding results in value=choice, key=count
    yield (choice, sum(counts))


if __name__ == '__main__':
MRPrepositionsFinder.run()

当我尝试在Hadoop集群上运行代码时，我使用了以下命令：

python hrc_discover.py /hdfs/user/user/HRCmail/* -r hadoop --hadoop-bin /usr/bin/hadoop > /hdfs/user/user/output 不幸的是，每次运行该命令时，都会出现以下错误：

No configs found; falling back on auto-configuration STDERR: Error: JAVA_HOME is not set and could not be found. Traceback (most recent call last): File "hrc_discover.py", line 37, in MRPrepositionsFinder.run() File "/usr/lib/python3.5/site-packages/mrjob-0.6.0.dev0-py3.5.egg/mrjob/job.py", line 432, in run mr_job.execute() File "/usr/lib/python3.5/site-packages/mrjob-0.6.0.dev0-py3.5.egg/mrjob/job.py", line 453, in execute super(MRJob, self).execute() File "/usr/lib/python3.5/site-packages/mrjob-0.6.0.dev0-py3.5.egg/mrjob/launch.py", line 161, in execute self.run_job() File "/usr/lib/python3.5/site-packages/mrjob-0.6.0.dev0-py3.5.egg/mrjob/launch.py", line 231, in run_job runner.run() File "/usr/lib/python3.5/site-packages/mrjob-0.6.0.dev0-py3.5.egg/mrjob/runner.py", line 437, in run self._run() File "/usr/lib/python3.5/site-packages/mrjob-0.6.0.dev0-py3.5.egg/mrjob/hadoop.py", line 346, in _run self._find_binaries_and_jars() File "/usr/lib/python3.5/site-packages/mrjob-0.6.0.dev0-py3.5.egg/mrjob/hadoop.py", line 361, in _find_binaries_and_jars self.get_hadoop_version() File "/usr/lib/python3.5/site-packages/mrjob-0.6.0.dev0-py3.5.egg/mrjob/hadoop.py", line 198, in get_hadoop_version return self.fs.get_hadoop_version() File "/usr/lib/python3.5/site-packages/mrjob-0.6.0.dev0-py3.5.egg/mrjob/fs/hadoop.py", line 117, in get_hadoop_version stdout = self.invoke_hadoop(['version'], return_stdout=True) File "/usr/lib/python3.5/site-packages/mrjob-0.6.0.dev0-py3.5.egg/mrjob/fs/hadoop.py", line 172, in invoke_hadoop raise CalledProcessError(proc.returncode, args) subprocess.CalledProcessError: Command '['/usr/bin/hadoop', 'version']' returned non-zero exit status 1 我环顾了一下互联网，发现我需要导出我的JAVA_HOME变量——但我不想设置任何可能破坏我的设置的东西

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在此方面的任何帮助都将不胜感激，谢谢

问题似乎出现在etc/hadoop/hadoop-env.sh脚本文件中

JAVA_HOME环境变量配置为：

export JAVA_HOME=$(JAVA_HOME)

因此，我继续将其更改为以下内容：

export JAVA_HOME=/usr/lib/jvm/java-8-openjdk

python hrc_discover.py /hdfs/user/user/HRCmail/* -r hadoop --hadoop-streaming-jar /usr/lib/hadoop/share/hadoop/tools/lib/hadoop-streaming-2.7.3.jar --hadoop-bin /usr/bin/hadoop > /hdfs/user/user/output

我尝试再次运行以下命令，希望它能正常工作：

python hrc_discover.py /hdfs/user/user/HRCmail/* -r hadoop --hadoop-bin /usr/bin/hadoop > /hdfs/user/user/output

谢天谢地，MRJob在JAVA_HOME环境中获得了以下输出：

No configs found; falling back on auto-configuration
Using Hadoop version 2.7.3
Looking for Hadoop streaming jar in /home/hadoop/contrib...
Looking for Hadoop streaming jar in /usr/lib/hadoop-mapreduce...
Hadoop streaming jar not found. Use --hadoop-streaming-jar
Creating temp directory /tmp/hrc_discover.user.20170306.022649.449218
Copying local files to hdfs:///user/user/tmp/mrjob/hrc_discover.user.20170306.022649.449218/files/...
.. 

为了解决Hadoop streaming jar的问题，我在命令中添加了以下开关：

--hadoop-streaming-jar /usr/lib/hadoop/share/hadoop/tools/lib/hadoop-streaming-2.7.3.jar

完整命令如下所示：

export JAVA_HOME=/usr/lib/jvm/java-8-openjdk

python hrc_discover.py /hdfs/user/user/HRCmail/* -r hadoop --hadoop-streaming-jar /usr/lib/hadoop/share/hadoop/tools/lib/hadoop-streaming-2.7.3.jar --hadoop-bin /usr/bin/hadoop > /hdfs/user/user/output

其结果为以下输出：

No configs found; falling back on auto-configuration
Using Hadoop version 2.7.3
Creating temp directory /tmp/hrc_discover.user.20170306.022649.449218
Copying local files to hdfs:///user/user/tmp/mrjob/hrc_discover.user.20170306.022649.449218/files/...

---

问题似乎已经解决，Hadoop应该处理我的工作。

如果我将机器设置为以伪分布式模式运行，并将本地数据文件放入hdfs中，这会有所帮助。