In-switch approximate processing: Delayed tasks management for MapReduce applications

In MapReduce, the parallel processing performance is often limited by only a few compute nodes that delay to complete given tasks. Although various techniques have been invented to handle such stragglers, these techniques mostly impose a burden on master node to monitor the progress of all the compute nodes, resulting in a new bottleneck as the number of compute nodes increases. As an alternative approach, in this paper, we propose to move such straggler management burden from master node to network switch that connects the master and compute nodes, because all the information goes through the switch. More specifically, the proposed network switch monitors output packets from Map tasks to detect stragglers. When detected, the proposed switch generates a response instead of the straggler based on the outputs of the other normal Map tasks, so that Reduce tasks can be started without delay. We introduce some approximate techniques for the proxy computation and response at the switch; thus our switch is called "ApproxSW." We implement ApproxSW on NetFPGA-SUME board that has four 10Gbit Ethernet (10GbE) interfaces and a Virtex-7 FPGA. An experiment shows that the ApproxSW functions do not degrade the original 10GbE switch performance. We also analyze the accuracy of the proxy computation and response for stragglers and show that the proposed approximation based on task similarity achieves the best accuracy.