Siddharth Vijayakrishnan discusses how web servers work and compares Apache to other web servers like Lighttpd. He explains that while Apache is popular, its multi-process model does not scale well under heavy loads. Lighttpd uses an event-driven model and single process design that allows it to outperform Apache in benchmarks. It has gained popularity as a faster alternative to Apache for serving dynamic content. The document also outlines future areas of improvement for Lighttpd.

1. Beyond Apache: Faster Web
Servers
Siddharth Vijayakrishnan
mail@bluefireworks.net
Beyond Apache: Faster Web Servers – p.1/11

2. About me
• Application developer with Oracle India
• Work on web servers in my free time
• Contributor to Lighttpd
Beyond Apache: Faster Web Servers – p.2/11

3. Executive summary
• How does a web server work?
• How can it made to work faster
• Apache
• Other web servers
• Lighttpd
• The road ahead
Beyond Apache: Faster Web Servers – p.3/11

4. Let’s write a web server
• First try:socket(), bind(), listen(),
accept(),sendresponse(), close()
• Second try: socket(), bind(),listen(), accept(),
fork() etc
• Second try better than the first since it can handle
multiple connections
• A lot of web servers do just this and work just fine
Beyond Apache: Faster Web Servers – p.4/11

5. What’s wrong then?
• This model does not scale well
• Model breaks down completely under overload
conditions
• Slashdot effect / "Thundering Herd" problem
• Distributed Denial of Service attacks
Beyond Apache: Faster Web Servers – p.5/11

6. Threads v/s Event Driven
• Threads:-
• Kernel schedulers are getting better at their
job
• Scales well on SMP systems
• Throughput degrades drastically under heavy
load
Beyond Apache: Faster Web Servers – p.6/11

7. Threads v/s Event Driven
• Event Driven:-
• Avoids the nasty beasties - synchronization,
dead lock, adaptive process spawning etc
• Scales nicely under overload
• A single process event driven design cannot
take advantage of SMP
• Blocking I/O can degrade performance of the
event driven model
Beyond Apache: Faster Web Servers – p.7/11

8. The Apache Web Server
• Poster child of the OSS revolution
• Feature rich
• Module API allows extensions to server
functionality
• Apache2 supports multiple processing models
• prefork
• worker
• experimental event driven mode
Beyond Apache: Faster Web Servers – p.8/11

9. What Ails Apache?
• Slow adoption of Apache2 (some stats here)
• Apache 1.3 (the most popular version) suffers
from generic multi process server scalability
issues
• Rich feature set can sometimes be a problem e.g
• httpd.conf / rewrite / virtual hosting are not
the easiest to get right
• Support for .htaccess slows down processing
Beyond Apache: Faster Web Servers – p.9/11

10. Others in the fray
• thttpd
• Really fast at serving static content
• Not much support for anything else
• zeus
• Fast but not open source
• Others:
• gatling, cherokee, boa, nginx, mathopd
• Matrix showing features present and lacking
Beyond Apache: Faster Web Servers – p.10/11

11. Experimental Efforts
• Tux (kernelspace httpd), Flash
• Inspired by the Mindcraft survey that showed
IIS to be faster than Apache
• Tux was a nice experiment till sendfile()
arrived
• Flash
• has an excellent specWEB 99 score
• Hybrid design model - Asymmetric
Multiprocess Event Driven
• Judicious use of threads to get around the
flaws in the event driven model
• Lazy Asynchronous I/O
Beyond Apache: Faster Web Servers – p.11/11

12. Lighttpd: A Viable Alternative
• Began as an experiment to prove that a web
server running as a single process could
withstand the thundering herds
• Stuff to be added here
Beyond Apache: Faster Web Servers – p.12/11

13. Lighttpd: Features
• Standard Set
• HTTP/1.1 support, SSL,
FastCGI,CGI,WebDAV, IPv6
• Module API available
• Unique Features
• Works with different event handlers
• Memcache integration
• Workarounds for most of the problems that
event driven servers face
• Really simple configuration
Beyond Apache: Faster Web Servers – p.13/11

14. Lighttpd: Currently
• 19,000 installations as per the last Netcraft survey
• Phenomenal growth rate in the number of servers
running lighty
• Release 1.4.7 is out
• Release early, Release often -> A release
every two or three weeks
• Enthusiastic response from the ’frameworks’
crowd
• RoR users form the most vocal support group
• Some popular sites running Lighttpd
• www.nexopia.com
• wikipedia image/download servers
• Textdrive Beyond Apache: Faster Web Servers – p.14/11

15. Lighttpd: How Does It Compare
• benchmark data goes here
Beyond Apache: Faster Web Servers – p.15/11

16. Lighttpd: Future
• Filters
• Windows port (if someone gets the time)
• Get the server into all major distributions
• More and more modules (contributions will be
gratefully accepted)
Beyond Apache: Faster Web Servers – p.16/11