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wordcount_hadoop.py
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wordcount_hadoop.py
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# -*- coding: utf-8 -*-
#
# Copyright 2012-2015 Spotify AB
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
import luigi
import luigi.hadoop
import luigi.hdfs
# To make this run, you probably want to edit /etc/luigi/client.cfg and add something like:
#
# [hadoop]
# jar: /usr/lib/hadoop-xyz/hadoop-streaming-xyz-123.jar
class InputText(luigi.ExternalTask):
"""
This task is a :py:class:`luigi.task.ExternalTask` which means it doesn't generate the
:py:meth:`~.InputText.output` target on its own instead relying on the execution something outside of Luigi
to produce it.
"""
date = luigi.DateParameter()
def output(self):
"""
Returns the target output for this task.
In this case, it expects a file to be present in HDFS.
:return: the target output for this task.
:rtype: object (:py:class:`luigi.target.Target`)
"""
return luigi.hdfs.HdfsTarget(self.date.strftime('/tmp/text/%Y-%m-%d.txt'))
class WordCount(luigi.hadoop.JobTask):
"""
This task runs a :py:class:`luigi.contrib.hadoop.JobTask`
over the target data returned by :py:meth:`~/.InputText.output` and
writes the result into its :py:meth:`~.WordCount.output` target.
This class uses :py:meth:`luigi.contrib.hadoop.JobTask.run`.
"""
date_interval = luigi.DateIntervalParameter()
def requires(self):
"""
This task's dependencies:
* :py:class:`~.InputText`
:return: list of object (:py:class:`luigi.task.Task`)
"""
return [InputText(date) for date in self.date_interval.dates()]
def output(self):
"""
Returns the target output for this task.
In this case, a successful execution of this task will create a file in HDFS.
:return: the target output for this task.
:rtype: object (:py:class:`luigi.target.Target`)
"""
return luigi.hdfs.HdfsTarget('/tmp/text-count/%s' % self.date_interval)
def mapper(self, line):
for word in line.strip().split():
yield word, 1
def reducer(self, key, values):
yield key, sum(values)
if __name__ == '__main__':
luigi.run()