Cottage: Coordinated Time Budget Assignment for Latency, Quality and Power Optimization in Web Search

Most CPU power management techniques for web search assume that the time budget for a query is given a priori. However, determining the time budget on a per query granularity is challenging, because a difficult trade-off between the search latency, quality and power consumption has to be made. In this paper, we present Cottage, a coordinated time budget assignment framework between the aggregator and Index Serving Nodes (ISNs), which employs two distinct distributed search latency and quality predictors. The prediction results are integrated at a centralized optimizer for selecting the proper search time budget, while cutting off slow and low quality ISNs. Cottage also accelerates slow ISNs that have a high quality contribution, thus improving search quality. The implementation results on the Solr search engine show that Cottage outperforms state-of-the-art approaches with a 54% latency reduction and 41.3% less consumed power. In addition, the P@10 search quality with Cottage can still be as good as 0.947.