DotSlash: A Self-configuring and Scalable Rescue System for Handling Web Hotspots Effectively

Speaker:	Weibin Zhao
		Columbia University

Title:		"DotSlash: A Self-configuring and Scalable Rescue System for
		 Handling Web Hotspots Effectively"

Date:		Thursday, 21 April 2005

Time:		3:00 pm - 4:00 pm

Venue:		Room 2404 (via lift nos. 17/18)
		HKUST


ABSTRACT:

Handling web hotspots (also known as flash crowds or the Slashdot effect)
is a challenging issue in designing today's web server systems.
Over-provisioning a web site is not only uneconomical but also difficult
since the peak load is hard to predict. To handle web hotspots
effectively, I developed DotSlash, a self-configuring and scalable rescue
system.

DotSlash allows different web sites to form a mutual-aid community, and
use spare capacity in the community to relieve web hotspots experienced by
any individual site. As a rescue system, DotSlash intervenes when a web
site becomes heavily loaded, and is phased out once the workload returns
to normal. The whole rescue process is self-managing in that service
discovery is used to allow servers of different web sites to learn about
each other dynamically, rescue actions are triggered automatically based
on load conditions, and a rescue server can serve the content of its
origin serves on the fly without the need of any advance configuration. I
have implemented a prototype of DotSlash on top of Apache. Experiments
show that using DotSlash a web server can increase the request rate it
supported and the data rate it delivered to clients by an order of
magnitude.

I also designed an extended version of DotSlash for dynamic content web
sites, and evaluated it in the context of the widely used LAMP
configuration (Linux, Apache, MySQL, and PHP). By supporting dynamic
replication of scripts from an origin server to its rescue servers, a
dynamic content web site can completely remove its web server bottleneck,
and support a request rate constrained only by the capacity of its
database server.


************************
Biography:

Weibin Zhao is currently a Ph.D. candidate in the Department of Computer
Science at Columbia University. He received his M.E. and B.E. in Computer
Science from Tsinghua University, China. Before joining Columbia
University, he was a researcher at the National Research Center for
Intelligent Computing Systems of China. His research is in the area of
computer networking and distributed systems.