Stateful bulk processing for incremental analytics.

ABSTRACTThis work addresses the need for stateful dataflow programs that can rapidly sift through huge, evolving data sets. These data-intensive applications perform complex multi-step computations over successive generations of data inflows, such as weekly web crawls, daily image/video uploads, log files, and growing social networks. While programmers may simply re-run the entire dataflow when new data arrives, this is grossly inefficient, increasing result latency and squandering hardware resources and energy. Alternatively, programmers may use prior results to incrementally incorporate the changes. However, current large-scale data processing tools, such as Map-Reduce or Dryad, limit how programmers incorporate and use state in data-parallel programs. Straightforward approaches to incorporating state can result in custom, fragile code and disappointing performance. This work presents a generalized architecture for continuous bulk processing (CBP) that raises the level of abstraction for building incremental applications. At its core is a flexible, groupwise processing operator that takes state as an explicit input. Unifying stateful programming with a data-parallel operator affords several fundamental opportunities for minimizing the movement of data in the underlying processing system. As case studies, we show how one can use a small set of flexible dataflow primitives to perform web analytics and mine large-scale, evolving graphs in an incremental fashion. Experiments with our prototype using real-world data indicate significant data movement and running time reductions relative to current practice. For example, incrementally computing PageRank using CBP can reduce data movement by 46% and cut running time in half.