如何在EMR上设置减速机数量

Question

我通过aws上的自定义jar步骤来运行一系列Mapper和Reducer任务。我只想通过一个reducer运行最后一个reducer任务。我该怎么办？

Answer 1

也许：

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来自：How do you force the number of reducers in a map reduce job to be higher? - Hortonworks

或者也许：

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发件人：hadoop - How does Hive choose the number of reducers for a job? - Stack Overflow

Answer 2

我已经通过将job.setNumReduceTasks（1）放入包含映射器和reducer的java文件的main方法中来解决了这个问题。