Hadoop简介
Hadoop是一个开源的分布式存储和计算框架,它可以在大量计算机集群上运行,提供高性能、高可用性和可扩展性的数据处理能力,Hadoop的核心组件包括HDFS(Hadoop Distributed FileSystem)和MapReduce,HDFS是一个分布式文件系统,用于存储大量的数据;MapReduce是一种编程模型,用于处理和生成大数据集。
PHP与Hadoop集成
PHP是一种广泛使用的服务器端脚本语言,可以通过Web服务与其他程序进行交互,要将PHP与Hadoop集成,可以使用PHP的Hadoop客户端库,如hadoop-php-client
,这个库提供了一个简单的API,可以方便地在PHP中执行Hadoop命令。
编写MapReduce程序
1、创建一个文本文件,包含一些单词,
hello world
hello php
hello mapreduce
2、编写一个Mapper类,继承自hadoop\mapreduce\Mapper
,并实现run()
方法,在run()
方法中,读取输入文件的每一行,然后使用str_word_count()
函数统计每个单词出现的次数,最后将结果输出到标准输出。
<?php namespace hadoop\mapreduce; use hadoop\mapreduceMapper; class WordCountMapper extends Mapper { public function run($input) { $lines = explode(" ", $input); foreach ($lines as $line) { $words = explode(" ", $line); foreach ($words as $word) { $this->emit(array($word => 1), 1); } } } } ?>
3、编写一个Reducer类,继承自hadoop\mapreduce\Reducer
,并实现run()
方法,在run()
方法中,接收Mapper输出的键值对,并对相同的键进行累加,最后将结果输出到标准输出。
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