title: Unusual Hadoop error - tasks get killed on their own
body: <p>When I run my hadoop job I get the following error:</p>
  
  <p><strong>Request received to kill task 'attempt_201202230353_23186_r_000004_0' by user
  Task has been KILLED_UNCLEAN by the user</strong></p>
  
  <p>The logs appear to be clean. I run 28 reducers, and this doesnt happen for all the reducers. It happens for a selected few and the reducer starts again. I fail to understand this. Also other thing I have noticed is that for a small dataset, I rarely see this error!</p>