I have a Yarn MR (with two ec2 instances to mapreduce) job on a dataset of approximately a thousand avro records, and the map phase is behaving erratically. See the progress below. Of course i checked the logs on resourcemanager and nodemanagers and saw nothing suspicious, but these logs are too verbose What is going on there ? hive> select * from nikon where qs_cs_s_aid='VIEW' limit 10; Total MapReduce jobs = 1 Launching Job 1 out of 1 Number of reduce tasks is set to 0 since there's no reduce operator Starting Job = job_1352281315350_0020, Tracking URL = http://blabla.ec2.internal:8088/proxy/application_1352281315350_0020/ Kill Command = /usr/lib/hadoop/bin/hadoop job -Dmapred.job.tracker=blabla.com:8032 -kill job_1352281315350_0020 Hadoop job information for Stage-1: number of mappers: 4; number of reducers: 0 2012-11-07 11:14:40,976 Stage-1 map = 0%, reduce = 0% 2012-11-07 11:15:06,136 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 10.38 sec 2012-11-07 11:15:07,253 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 12.18 sec 2012-11-07 11:15:08,371 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 12.18 sec 2012-11-07 11:15:09,491 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 12.18 sec 2012-11-07 11:15:10,643 Stage-1 map = 2%, reduce = 0%, Cumulative CPU 15.42 sec (...) 2012-11-07 11:15:35,441 Stage-1 map = 28%, reduce = 0%, Cumulative CPU 37.77 sec 2012-11-07 11:15:36,486 Stage-1 map = 28%, reduce = 0%, Cumulative CPU 37.77 sec here restart at 16% ? 2012-11-07 11:15:37,692 Stage-1 map = 16%, reduce = 0%, Cumulative CPU 21.15 sec 2012-11-07 11:15:38,815 Stage-1 map = 16%, reduce = 0%, Cumulative CPU 21.15 sec 2012-11-07 11:15:39,865 Stage-1 map = 16%, reduce = 0%, Cumulative CPU 21.15 sec 2012-11-07 11:15:41,064 Stage-1 map = 18%, reduce = 0%, Cumulative CPU 22.4 sec 2012-11-07 11:15:42,181 Stage-1 map = 18%, reduce = 0%, Cumulative CPU 22.4 sec 2012-11-07 11:15:43,299 Stage-1 map = 18%, reduce = 0%, Cumulative CPU 22.4 sec here restart at 0% ? 2012-11-07 11:15:44,418 Stage-1 map = 0%, reduce = 0% 2012-11-07 11:16:02,076 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 6.86 sec 2012-11-07 11:16:03,193 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 6.86 sec 2012-11-07 11:16:04,259 Stage-1 map = 2%, reduce = 0%, Cumulative CPU 8.45 sec (...) 2012-11-07 11:16:31,291 Stage-1 map = 22%, reduce = 0%, Cumulative CPU 35.34 sec 2012-11-07 11:16:32,414 Stage-1 map = 26%, reduce = 0%, Cumulative CPU 37.93 sec here restart at 11% ? 2012-11-07 11:16:33,459 Stage-1 map = 11%, reduce = 0%, Cumulative CPU 19.53 sec 2012-11-07 11:16:34,507 Stage-1 map = 11%, reduce = 0%, Cumulative CPU 19.53 sec 2012-11-07 11:16:35,731 Stage-1 map = 13%, reduce = 0%, Cumulative CPU 21.47 sec (...) 2012-11-07 11:16:46,839 Stage-1 map = 17%, reduce = 0%, Cumulative CPU 24.14 sec here restart at 0% ? 2012-11-07 11:16:47,939 Stage-1 map = 0%, reduce = 0% 2012-11-07 11:16:56,653 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 7.54 sec 2012-11-07 11:16:57,814 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 7.54 sec (...) Needless to say the job crashes after some time with an Error: java.io.IOException: java.io.IOException: java.lang.ArrayIndexOutOfBoundsException: -56