1. Sorting the values before they are send to the reducer stackoverflow.com
I'm thinking about building a small testing application in hadoop to get the hang of the system. The application I have in mind will be in the realm of doing statistics. I want ...
2. Hadoop: Do not re-schedule a failed reducer stackoverflow.com
This is how Hadoop currently works: If a reducer fails (throws a NullPointerException for example), Hadoop will reschedule another reducer to do the task of the reducer that failed. Is it possible ...
3. hadoop + Writable interface + readFields throws an exception in reducer stackoverflow.com
I have a simple map-reduce program in which my map and reduce primitives look like this
map(K,V) = (Text, OutputAggregator)
4. Hadoop reducer string manipulation doesn't work stackoverflow.com
Hi Text manipulation in Reduce phase seems not working correctly. I suspect problem could be in my code rather then hadoop itself but you never know... If you can spot any gotchas let ...
5. Accessing a mapper's counter from a reducer stackoverflow.com
I need to access the counters from my mapper in my reducer. Is this possible? If so how is it done? As an example: my mapper is: public class CounterMapper extends Mapper ...
6. Do something to the entire Reducer values list based on one element stackoverflow.com
I have an interesting problem that I'm struggling to fit in MapReduce. I have a bunch of log entries. What I need to do is something like this: Check if any entry ...
7. Hadoop, how to compress mapper output but not the reducer output stackoverflow.com
I have a mapreduce java program in which I try to only compress the mapper output but not the reducer output. I thought that this would be possible by setting ...
8. Hadoop: Mapper is getting executed but reducer is not stackoverflow.com
Basically I want to do following:
9. null buffer in ReadFields() in reducer for complex types stackoverflow.com
i am trying to pass a complex writable between mapper and reducer, more specifically ArrayWritable of ObjectWritables.
10. Hadoop streaming reducer doesn't produce any output when input is empty stackoverflow.com
The following hadoop streaming behavior seems unintuitive and undocumented, if not outright a bug: Mapper:
11. Hadoop Looping the Reducer stackoverflow.com
I am trying to find a way to "loop" my reducer, for example:
12. concatenating reducer outputs from SequenceFileOutputFormat stackoverflow.com
I've got a job that uses 100 reducers config'ed with setOutputFormat (SequenceFileOutputFormat.class); After the job runs, can I combine all of the part files via the following command and have things work correctly with the ...
13. Hadoop 0.20.2 reducer throws ArrayIndexOutOfBoundsException when iterating values stackoverflow.com
I am fairly new to hadoop, however, I've been reading "Hadoop: The definitive guide", so I think I have an understanding of the basic concepts. I used Hadoop 0.20.2 to run a ...
14. Hadoop Reducer unable to accumulate all values in one iteration stackoverflow.com
I have a basic scenario in Hadoop: All mappers send all values to the same key. Therefore all values end up on the same reducer. However, when I iterate the values in the ...