Hi, I am building a MapReduce application that constructs the adjacency list of a graph from an input edge list. I noticed that my Reduce phase always hangs (and timeout eventually) as it calls the function context.write(Key_x,Value_x) when the Value_x is a very large ArrayWritable (around 4M elements). I have increased both "mapred.task.timeout" and the Reducers memory but no luck; the reducer does not finish the job. Is there any other data format that supports large amount of data or should I use my own "OutputFormat" class to optimize writing the large amount of data?
Thank you. Zuhair Khayyat
