Predoop: Preempting Reduce Task for Job Execution Accelerations

Abstract

Map/Reduce is a popular parallel processing framework for data intensive computing. For overlapping the Map task’s execution phase and the Reduce task’s intermediate data fetching and merging phase, existing Map/Reduce schedulers always pre-launch the Reduce task at the specific threshold where its map tasks have been launched, and this pattern incurs the occupation of the consuming resources of the reduce task during its idle time on waiting for fetching the intermediate data from map tasks. To address this issue, we propose an extension version of Hadoop map/reduce framework, called Predoop, in this paper. The basic idea of Predoop is to preempt the reduce task during its idle time and allocate the released resource to the map tasks on schedule. To achieve this goal, first, we introduce the preemptive mechanism for reduce tasks and map tasks respectively to enable Map/Reduce tasks to be preempted or resumed with correct status; second, we adopt the preempting-resuming model for the reduce task with the consideration of the progress of Reduce task data fetching & merging and the Map task execution so as to determine the timing of Reduce task preemption and resuming; third, we introduce the preemption-aware task scheduling strategy to allocate the released resources to the on-schedule Map tasks with the consideration of data locality. Experimental result demonstrates that Predoop outperforms Hadoop on various workload and the average job turnaround time can be reduced by maximum of 66.57 %.