Hadoop The Definitive Guide 4th Editon

最新推荐文章于 2017-07-02 23:42:56 发布

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最新推荐文章于 2017-07-02 23:42:56 发布

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本文深入探讨了Hadoop MapReduce的基本原理与操作流程，包括如何将输入数据划分成固定大小的切片，以及如何通过map和reduce任务进行数据处理。此外，还介绍了如何通过设置combiner函数来减少map与reduce之间的数据传输。

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Hadoop The Definitive Guide 4th Editon

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I.[Hadoop Fundamentals]

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1.Meet Hadoop

2.MapReduce

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Hadoop provides its own set of basic types that are optimized for network serialization

Hadoop divides the input to a MapReduce job into fixed-size pieces called input splits, or just splits. Hadoop creates one map task for each split, which runs the user-defined map function for each record in the split.

To minimize the data transferred between map and reduce tasks. Hadoop allows the user to specify a combiner function to be run on the map output, and the combiner function’s output forms the input to the reduce function.

Sample 问题：

1.脚本获取NCDC数据

2.hadoop获取

调用load_ncds.sh 获取NCDC数据时出现PipeMapRed.waitOutputThreads(): subprocess failed with code 127，错误码参考：http://blog.youkuaiyun.com/oDaiLiDong/article/details/46803603

增加对was的支持,由于找不到aws的 accesskey ，此方法暂未解决。

For some reason, the jar hadoop-aws-[version].jar which contains the implementation to NativeS3FileSystem is not present in the classpath of hadoop by default in the version 2.6 & 2.7. So, try and add it to the classpath by adding the following line in hadoop-env.sh which is located in $HADOOP_HOME/etc/hadoop/ hadoop-env.sh:

export HADOOP_CLASSPATH=$HADOOP_CLASSPATH:$HADOOP_HOME/share/hadoop/tools/lib/*

Assuming you are using Apache Hadoop 2.6 or 2.7

http://stackoverflow.com/questions/28029134/how-can-i-access-s3-s3n-from-a-local-hadoop-2-6-installation