Hi guys, I have a quick question regarding to fire scheduler of Hadoop, I am reading this article => http://blog.cloudera.com/blog/2008/11/job-scheduling-in-hadoop/, my question is from the following statements, "There is currently no support for preemption of long tasks, but this is being added in HADOOP-4665<https://issues.apache.org/jira/browse/HADOOP-4665>, which will allow you to set how long each pool will wait before preempting other jobs’ tasks to reach its guaranteed capacity.".
My questions are, 1. What means "preemption of long tasks"? Kill long running tasks, or pause long running tasks to give resources to other tasks, or it means something else? 2. I am also confused about "set how long each pool will wait before preempting other jobs’ tasks to reach its guaranteed capacity"., what means "reach its guaranteed capacity"? I think when using fair scheduler, each pool has predefined resources allocation settings (and the settings guarantees each pool has resources as configured), is that true? In what situations each pool will not have its guaranteed (or configured) capacity? regards, Lin
