[MAPREDUCE-2512] wait(5000) and notify() mechanism can be implemented instead of sleep(5000) in reduce task when there are no copies in progress and no new copies to schedule

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 0.20.2
• Component/s: task
• Assignee: Unassigned
• Reporter: Devaraj Kavali
• Created: 18/May/11 15:48
• Updated: 19/Apr/12 05:07
• Resolved: 19/Apr/12 05:07

Description

ReduceTask.java

 
       try { 
            if (numInFlight == 0 && numScheduled == 0) { 
              // we should indicate progress as we don't want TT to think 
              // we're stuck and kill us 
              reporter.progress(); 
              Thread.sleep(5000); 
            } 
          } catch (InterruptedException e) { } // IGNORE 

Here if we have no copies in flight and we can't schedule anything new, it is going to wait for 5000 millis. Instead of waiting for 5000 millis, this thread can wait with timeout and GetMapEventsThread can notify it if gets new map completion events earlier than 5000 millis time.