A Distributed Operating System for Web Servers JUSTIN LYNCH June 21, 2015June 21, 2015June 21, 2015 CPSC450/550 OPERATING SYSTEMS II DEPARTMENT OF PHYSICS, COMPUTER SCIENCE AND ENGINEERING CHRISTOPHER NEWPORT UNIVERSITY

Problem Description  The World Wide Web is more popular than ever and the demands on the content providers are higher than ever. Popular sites can now get a million of hits a day or more.  Sites can experience huge influxes in visits, smaller sites can especially be affected by surges in traffic by being mentioned by other larger sites.  When sites experience these huge influxes they are either forced to take down content or are effectively shutdown.

Aim & Objectives  As an avid user of internet I am often affected by many of these problems. One popular site I visit, is famous for knocking little sites offline.  While people are usually willing to co-host these sites, there is no system in place to ensure the author gets credit and that the sites remain unedited, not to mention its hard to mirror a site that is already down.  My objective is to show how distributed operating systems are well suited for spreading the loads placed on web servers.

Significance of points  Running a web server today requires most sites to keep extra hardware and bandwidth on hand even though most of the time this hardware is not needed. While it is true that internet usage is on the raise, many sites experience momentary surges in traffic when the larger sites mention them or they release new software.  Today’s website’s often incorporate server generated dynamic content – JSP and ASP - that proxy servers have trouble caching and even when pages do not have any it requires the proxy server to be setup by the users or isp’s of the users rather than the server administrators of the websites that need the help.  Distributed operating systems could be helpful in spreading the load across other providers that are not currently experiencing surges.

Significance of points continued  If a score-keeping service was created you could ensure that no one was abusing the service and you could prove to the bigger sites that they were not only taking on more of a load then they already have – as it is likely that they would be a source of bandwidth when a smaller suddenly has a surge of usage.  The Sprite Distributed Operating System could be modified to incorporate this service and is designed to work with powerful individual systems, giving the owners of those systems preference over work for remote users and to work without CPU pools and high-speed interconnects.  Everyone who downloads software or surfs the web would benefit from the pages being served from sites that are physically located closer.

Suggested Solutions  One way to relieve the problems of momentary surges in usage would be to switch the web servers over to a distributed operating system that connects many or all of the web servers on the internet together.  This would allow the sites to help one another when one gets a momentary spike in usage.  To ensure no one abuses the system, a score keeping system would have to be made.  Larger sites would want to join because requests for them would be filled by servers physically located closer to the web surfers.  Finally because the systems would be sharing a single system image even dynamic content, like JSP/ASPs, would be hosted across the system without worrying about having any problems that are sometimes associated with proxies.

Example of web request being fulfilled with normal web loads Located on east coast Located on west coast Surfer Located on east coast 1. User types in URL for a popular site 2. Popular site detects user is on east coast and points the user to a small site that is located on east coast 3. The small site fulfills all requests from the user for a block of time or until its traffic reaches 90% capacity

Example of smaller site getting a spike in requests Small east cost site Popular west coast site Popular east coast site Smaller site is serving web pages for itself and the popular west coast site to people in the east coast Readers of popular west coast site Readers of the smaller site Requests for the smaller site increase to 70% of smaller server’s capacity Smaller site ensures that other sites with the capacity to take on additional request have complete up to date copies of it in their caches Requests for the smaller site increase to 90% All requests for the popular west coast site are redirected to original host to be handled Requests for the smaller site increase to 95% of capacity All new requests for pages are now handed off to the closest server until levels drop to near normal levels Additional Readers of the small site on the west coast Additional east cost readers of smaller site

Suggested Methodology for the solution  I would recommend that the Sprite distributed operating system be modified to include the score keeper and a modern web server like Apache.  The sprite distributed operating system is the ideal distributed operating system because it was designed around the idea of connecting powerful machines together and giving priority to work being down on them by the owner of the machine. And it does this efficiently without high-speed interconnects.  The main downside of Sprite is that it is currently extremely out of date with work on it having been frozen in 94.  However, the Amoeba and Plan 9 operating systems were designed around having pools of CPUs interconnected with high-speed connections and this simply does not match how the web servers are setup.

Executive Summary  The World Wide Web continues to see increased traffic, especially from users overseas.  Many sites with smaller user bases experience surges in use, that often effectively disables the site until the surge is over.  I think the Sprite distributed operating system could help solve these problems.

References  Bosse. Stefan Fireball Software Distribution FSD-2002A. amoeba.sourceforge.net amoeba.sourceforge.nethttp://fsd- amoeba.sourceforge.net  Cox, Russ. Grosse, Eric. Pike, Rob. Presotto, Dave. Quinlan, Sean. Security in Plan  Douglis, Fred. Ousterhout, John K. Kaashoek, M. Frans. Tanenbaum, Andrew S. A  Comparison of Two Distributed Systems: Amoeba and Sprite. ftp://ftp.cs.berkeley.edu/ucb/sprite/papers/amoeba-sprite.ps ftp://ftp.cs.berkeley.edu/ucb/sprite/papers/amoeba-sprite.ps  Ousterhout, John. A Brief Retrospective on the Sprite Network Operating System.  Pike, Rob, Presotto, Dave. Dorward Sean. Flandrena Bob. Thompson, Ken. Trickey, Howard. Winterbottom, Phil. Plan 9 from Bell Labs.  Shirriff, Ken. The Sprite Operating System.