I am new in mapreduce and hadoop (hadoop 3.2.3 and java 8). I am trying to separate some lines based on a symbol in a line. Example: “q1,a,q0,” should be return (‘a’,”q1,a,q0,”) as (key, value). My dataset contains ten(10) lines , five(5) for key ‘a’ and five fo…
Tag: mapreduce
MapReduce filtering to get customers not in order list?
Currently learning on MapReduce and trying to figure out how to code this into Java. Two input files, called customers.txt and car_orders.txt: customers.txt =================== 12345 Peter 12346 …
Unable to submit concurrent Hadoop jobs
I am running Hadoop 2.7 on my local machine, along with HBase 1.4 and Phoenix 4.15. I have written an application which submits map reduce jobs that delete data in HBase through Phoenix. Each job is run by an individual thread of a ThreadPoolExecutor and looks like this: Everything is fine if there is only 1 …
Reducer doesn’t call reduce method when using my own class as output value MapReduce Hadoop
I was trying to use my own Class object as the output value of my Mapper and use them inside the Reducer but the reduce() method isn’t called and my app was going to be terminated if I remove the default constructor of DateIncome class. I wrote my codes as follows: Driver: Mapper: Reducer: DateIncome: I…
How to copy/assign a CompositeKey into another CompositeKey in hadoop?
I try running a map reduce on some data on a cluster and get the following output. This is my reducer From what I understand the problem is that hadoop treats lastCK and key as the same object and this condition will always be true This is my CompositeKey class I tried changing setters to something along this…
/bin/bash: /bin/java: No such file or directory error in Yarn apps in MacOS
I was trying to run a simple wordcount MapReduce Program using Java 1.7 SDK and Hadoop2.7.1 on Mac OS X EL Captain 10.11 and I am getting the following error message in my container log “stderr” /bin/bash: /bin/java: No such file or directory Application Log- Command I am Running My ENV variable a…
Map Reduce flow in Hadoop
I’m learning Hadoop using the book Hadoop in Practice, and while reading chapter 1 i came across this diagram: From the Hadoop docs:(http://hadoop.apache.org/docs/current2/api/org/apache/hadoop/mapred/Reducer.html) 1.Shuffle Reducer is input the grouped output of a Mapper. In the phase the framework, fo…
How to build OpenCV with Java under Linux using command line?(Gonna use it in MapReduce)
Recently I’m trying OpenCV out for my graduation project. I’ve had some success under Windows enviroment. And because with Windows package of OpenCV it comes with pre-built libraries, so I don’t have to worry about how to build them. But since the project is suppose to run on a cluster with …