Q-Cop: Avoiding Bad Query Mixes to Minimize Client Timeouts Under Heavy Loads

In three-tiered web applications, some form of admission control is required to ensure that throughput and response times are not significantly harmed during periods of heavy load. We propose Q-Cop, a prototype system for improving admission control decisions that considers a combination of the load on the system, the number of simultaneous queries being executed, the actual mix of queries being executed, and the expected time a user may wait for a reply before they or their browser give up (i.e., time out). Using TPC-W queries, we show that the response times of different types of queries can vary significantly depending not just on the number of queries being processed but on the mix of other queries that are running simultaneously. We develop a model of expected query execution times that accounts for the mix of queries being executed and integrate this model into a three-tiered system to make admission control decisions. Our results show that this approach makes more informed decis...

• Type: Conference
• Year: 2010
• Where: ICDE
• Authors: Sean Tozer, Tim Brecht, Ashraf Aboulnaga
• Keywords: Admission Control Decisions, Database, ICDE 2010, Simultaneous Queries, TPC-W Queries