Major Description
when Nutch is running on Hadoop , based on map-reduce concept, each map task do some thing on it's owned data, so, each fetcher map-task work with it's Queues and do not know any thing about other Queus. so, enforce delay between successive requests and maximum concurrent requests policies on it's Queues. but with a simple test we found that it's not good piliteness mechanism when we have multiple map tasks.