Managing the Response Time for Multi-tiered Web Applications

We present a system for managing the response time of web applications. This system allows service providers to group web application requests into different classes and assign response time goals to these classes of requests. We manage response times by using mechanisms that control the
amount of server resources allocated to each class of web requests.We show how our platform can manage complex multitiered applications where each request uses multiple resources distributed over multiple tiers. We consider the case of a data center that supports multiple web applications, with each web application deployed and replicated on different but overlapping subsets of machines. We also show how our system can produce resource request signals that can guide another system that dynamically adjusts the application deployments. We also show how our system can manage heterogeneous requests by taking into account the amount of resources that each request consumes at each tier. To manage the response times of web requests we introduce an additional tier, the Proxy tier. The proxy adds layer-7 mechanisms that divide and control the flow of requests into the application tiers. We use a feedback control loop that periodically adjusts the resources allocated to each class. The feedback controller uses an approximate first-principles model of the system, with parameters derived from continuous monitoring. We discuss our prototype implementation and report experimental results that show the dynamic behavior of the system.