Computational skewness is a significant challenge in multi-tenant data-parallel clusters that introduce dynamic heterogeneity of machine capacity in distributed data processing. Previous efforts to addressing skewness mostly focus on batch jobs based on the assumption that processing time is linearly dependent on the size of partitioned data. However, they are illsuited for iterative machine learning (ML) jobs, which (1) exhibit a non-linear relationship between the size of partitioned parameters and processing time within each iteration, and (2) show an explicit binding relationship between input data and parameters for parameter update. In this paper, we present FlexPara, a parameter partition approach that leverages the non-linear relationship and provisions adaptive tasks to match the distinct machine capacity so as to address the skewness in iterative ML jobs on data-parallel clusters. FlexPara first predicts task processing time based on a capacity model designed for iterative ML jobs without the linear assumption. It then partitions parameters to parallel tasks through proactive parameter reassignment. Such reassignment can significantly reduce network transmission cost incurred by input data movement due to the binding relationship. We implement FlexPara in Spark and evaluate it with various ML jobs. Experimental results show that compared to hash partition, FlexPara speeds up the execution by up to 54% and 43% in private and NSF Chameleon clusters, respectively.

The tremendous growth of cloud computing and large-scale data analytics highlight the importance of reducing datacenter power consumption and environmental impact of brown energy. While many Internet service operators have at least partially powered their datacenters by green energy, it is challenging to effectively utilize green energy due to the intermittency of renewable sources, such as solar or wind. We find that the geographical diversity of internet-scale services can be carefully scheduled to improve the efficiency of applying green energy in datacenters. In this paper, we propose a holistic heterogeneity-aware cloud workload management approach, sCloud, that aims to maximize the system goodput in distributed self-sustainable datacenters. sCloud adaptively places the transactional workload to distributed datacenters, allocates the available resource to heterogeneous workloads in each datacenter, and migrates batch jobs across datacenters, while taking into account the green power availability and QoS requirements. We formulate the transactional workload placement as a constrained optimization problem that can be solved by nonlinear programming. Then, we propose a batch job migration algorithm to further improve the system goodput when the green power supply varies widely at different locations. Finally, we extend sCloud by integrating a flexible batch job manager to dynamically control the job execution progress without violating the deadlines. We have implemented sCloud in a university cloud testbed with real-world weather conditions and workload traces. Experimental results demonstrate sCloud can achieve near-to-optimal system performance while being resilient to dynamic power availability. sCloud with the flexible batch job management approach outperforms a heterogeneity-oblivious approach by 37 percent in improving system goodput and 33 percent in reducing QoS violations.

Understanding and troubleshooting distributed systems in the cloud is considered a very difficult problem because the execution of a single user request is distributed to multiple machines. Further, the multi-tenancy nature of cloud environments further introduces interference that causes performance issues. Most existing troubleshooting tools either focus on log analysis or intrusive tracing methods, leaving resource usage monitoring unexplored.

While Hadoop ecosystems become increasingly important for practitioners of large-scale data analysis, they also incur tremendous energy cost. This trend is driving up the need for designing energy-efficient Hadoop clusters in order to reduce the operational costs and the carbon emission associated with its energy consumption. However, despite extensive studies of the problem, existing approaches for energy efficiency have not fully considered the heterogeneity of both workload and machine hardware found in production environments. In this paper, we find that heterogeneity-oblivious task assignment approaches are detrimental to both performance and energy efficiency of Hadoop clusters. Our observation shows that even heterogeneity-aware techniques that aim to reduce the job completion time do not guarantee a reduction in energy consumption of heterogeneous machines. We propose a heterogeneity-aware task assignment approach, E-Ant, that aims to improve the overall energy consumption in a heterogeneous Hadoop cluster without sacrificing job performance. It adaptively schedules heterogeneous workloads on energy-efficient machines, without a priori knowledge of the workload properties. E-Ant employs an ant colony optimization approach that generates task assignment solutions based on the feedback of each task's energy consumption reported by Hadoop TaskTrackers in an agile way. Furthermore, we integrate DVFS technique with E-Ant to further improve the energy efficiency of heterogeneous Hadoop clusters. It relies on a DVFS controller to dynamically scale the CPU frequency of each slave machine in response to time-varying resource demands. Experimental results on a heterogeneous cluster with varying hardware capabilities show that E-Ant with DVFS improves the overall energy savings for a synthetic workload from Microsoft by 23 and 17 percent compared to Fair Scheduler and Tarazu, respectively.