hadoop - Mapreduce for dummies - Stack Overflow
2012年1月13日 · Hadoop can be used for a wide variety of problems. Check this blog entry from atbrox. Also, there is a lot of information on the internet about Hadoop and MapReduce and it's easy to get lost. So, here is the consolidated list of resources on Hadoop. BTW, Hadoop - The Definitive Guide 3rd edition is due in May.
Chaining multiple MapReduce jobs in Hadoop - Stack Overflow
2010年3月23日 · In many real-life situations where you apply MapReduce, the final algorithms end up being several MapReduce steps. i.e. Map1 , Reduce1 , Map2 , Reduce2 , and so on. So you have the output from th...
mapreduce - Hadoop - get results from output files after reduce ...
2013年8月26日 · In mapreduce you specify an output folder, the only thing it will contain will be part-r files (which is the output of a reduce task) and a _SUCCESS file (which is empty). So i think if you want to do postprocessing you only need to set the output dir of …
hadoop - MapReduce job Output sort order - Stack Overflow
2015年11月3日 · Partioner is the class which divides the key space in mapreduce. The default partioner ( Hashpartioner ) evenly divides the key space into the number of reducers. Check out this example for writing a custom partioner.
Understanding MapReduce in Hadoop 1.x - Stack Overflow
2017年3月31日 · MapReduce is the programming model for data processing (in Hadoop). Its implementation in Hadoop-1.x is often referred as the Classic MapReduce Implementation (or MapReduce v1) which uses JobTracker and TaskTrackers of Hadoop for the execution of Jobs and its corresponding APIs (user-facing client-side features) for writing them.
hadoop - manipulating iterator in mapreduce - Stack Overflow
I am trying to find the sum of any given points using hadoop, The issue I am having is on getting all values from a given key in a single reducer. It looks like this. Reducer: public static class
hadoop - Setting the number of map tasks and reduce tasks
2011年7月31日 · In the newer version of Hadoop, there are much more granular mapreduce.job.running.map.limit and mapreduce.job.running.reduce.limit which allows you to set the mapper and reducer count irrespective of hdfs file split size. This is helpful if you are under constraint to not take up large resources in the cluster.
(Hadoop) MapReduce - Chain jobs - JobControl doesn't stop
Applications should implement Tool for the same. 12/09/11 19:06:25 INFO input.FileInputFormat: Total input paths to process : 1 12/09/11 19:06:25 INFO util.NativeCodeLoader: Loaded the native-hadoop library 12/09/11 19:06:25 WARN snappy.LoadSnappy: Snappy native library not loaded 12/09/11 19:07:00 WARN mapred.JobClient: Use ...
hadoop - Number of MapReduce tasks - Stack Overflow
2017年2月24日 · mapreduce.input.fileinputformat.split.maxsize are at their default, the input split size for a file will be approximately equal to its blocksize considering the file is splittable. The total number of map tasks will be equal to sum of number of input splits per file.
hadoop - Java Heap Space error while executing Mapreduce
2002年3月16日 · Check memory settings for YARN, Map and Reduce tasks as per this article.. Set memory parameters depending on your input data set size.