Scheduling of MapReduce jobs is an integral part of Hadoop and effective job scheduling has a direct impact on Hadoop performance. Data locality is one of the most important factors to be considered in order to improve efficiency, as it affects data transmission through the system. A number of researchers have suggested approaches for improving data locality, but few have considered cache locality. In this paper, we present a state-of-the-art job scheduler, CLQLMRS (Cache Locality with Q-Learning in MapReduce Scheduler) for improving both data locality and cache locality using reinforcement learning. The proposed algorithm is evaluated by various experiments in a heterogeneous environment. Experimental results show significantly decreased execution time compared with FIFO, Delay, and the Adaptive Cache Local scheduler.
Hadoop is an open-source framework that enables the parallel processing of large data sets across a cluster of machines. It faces several challenges that can lead to poor performance, such as I/O operations, network data transmission, and high data access time. In recent years, researchers have explored prefetching techniques to reduce the data access time as a potential solution to these problems. Nevertheless, several issues must be considered to optimize the prefetching mechanism. These include launching the prefetch at an appropriate time to avoid conflicts with other operations and minimize waiting time, determining the amount of prefetched data to avoid overload and underload, and placing the prefetched data in a location that can be accessed efficiently when required. In this paper, we propose a smart prefetch mechanism that consists of three phases designed to address these issues. First, we enhance the task progress rate to calculate the optimal time for triggering prefetch operations. Next, we utilize K-Nearest Neighbor (KNN) clustering to identify which data blocks should be prefetched in each round, employing the data locality feature to determine the placement of prefetched data. Our experimental results demonstrate that our proposed smart prefetch mechanism improves job execution time by an average of 28.33% by increasing the rate of local tasks.
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