Self Adapting Web Servers Based on Hosted Applications by Hussain Alsaeed 10/12/2009

Outline Introduction Background Related Work Methodology Testbed Results and Analysis Conclusion Questions

Introduction The problem: The overloading of a web server when a hosted application is accessed heavily by clients The goal: To find a mechanism that will balance the load coming to a single web server based on the characteristics of the load (based on the hosted applications)

General Description of the Solution Use divide and conquer approach Classify hosted applications into different classes Determine the system’s resources that could become potential bottlenecks for each class Manage the system’s resources to handle overloading situations Use an admission control mechanism to avoid performance degradation

Motivation To use different configurations for instances in a distributed system To have a proactive approach in administering web servers.

Background Chandra et al. (2006)

Related Work Chandra et al. (2006), An observation-based approach towards self-managing web servers Chen et al. (2003), ACES: An efficient admission control scheme for QoS-aware web servers Chang et al. (2000),Adaptive-level memory caches on World Wide Web servers [3]

Methodology

CPU Adaptation: 2.6 Kernel Scheduler Dynamic Supports load balancing for Symmetric Multiprocessing (SMP) systems Operates in constant time O(1) Jones (2006)

Admission Control: Traffic Control Command (tc) prio: Priority Queue Discipline sfq: Stochastic Fairness Queueing tpf: Token Bucket Filter =iptables

Classifier: iptables command=tc command=tc Class of applicationSource IP address Static web requests High priority (1:1) Dynamic web requests Low priority (1:2)

Hardware of Testbed Server Operating SystemLinux Processing powerIntel Core Due of 2 GHz speed Memory3 GB of RAM Client 1 Operating SystemWindows Vista Processing powerIntel Core Due of 2 GHz speed Memory4 GB of RAM Client 2 Operating SystemWindows Vista Processing powerIntel Centrino of 1.7 GHz speed Memory2 GB of RAM

Software of Testbed Installed and configured Apache web server in the server machine Used Gnome-System-Monitor to find potential bottlenecks. library.gnome.org /users/gnome- system-monitor/ Installed and configure Jmeter in client 1 to generate http requests of static web pages. http: //jakarta.apache.org/jmeter/ http: //jakarta.apache.org/jmeter/ Used client 2 to generate requests of dynamic web pages (cgi)

Results & Analysis Class of applicationsCPU avg. load before the new system CPU avg. load after using the new system static web requests15% dynamic web requests55%54% static & dynamic web requests 80%56%

Conclusion The suggested solution can become a base for future work Other classes of applications Other techniques Other system’s resources

References [1]A. Chandra, P. Pradhan, R. Tawari, S. Sahu, and P. Shenoy, “An observation-based approach towards self-managing web servers,” Computer Communications, vol. 29, 2006, pp. 1174–1188. [2] X. Chen, H. Chen, and P. Mohapatra, "ACES: An efficent admission control scheme for QoS-aware web servers,” Computer Communications, vol. 26, 2003, pp. 1581–1593. [3]D.W. Chang, H.R. Ke, and R.C. Chang, “Adaptive-level memory caches on World Wide Web servers,” Computer Networks, vol. 32, 2000, pp [4]P. Goyal, X. Guo, and H. Vin, A hierarchical CPU scheduler for multimedia operating systems in: Proc. the Symp. Operating Systems Design and Implementation (OSDI 96), Oct. 1996, pp [5]T. Voigt, R. Tewari, D. Freimuth, and A. Mehra, Kernel mechanisms for service differentiation in overloaded web servers in: Proc. of the Usenix Annual Technical Conference 2001.

Thanks Q & A