Abstract
Unpredictability in query runtimes can arise in a shared cluster as a result of resource contentions caused by inter-query interactions. iQCAR - inter Query Contention AnalyzeR is a system that formally models these interferences between concurrent queries and provides a framework to attribute blame for contentions. iQCAR leverages a multi-level directed acyclic graph called iQC-Graph to diagnose the aberrations in query schedules that lead to these resource contentions. The demonstration will enable users to perform a step-wise deep exploration of such resource contentions faced by a query at various stages of its execution. The interface will allow users to identify top-k victims and sources of contentions, diagnose high-contention nodes and resources in the cluster, and rank their impacts on the performance of a query. Users will also be able to navigate through a set of rules recommended by iQCAR to compare how application of each rule by the cluster scheduler resolves the contentions in subsequent executions.