Would you like to know how to build an application server from scratch? This talk would provide an insight to the thought process and the key decisions made while building WebROaR from grounds up using C & Ruby. What enables this server to deliver high performance and also offer a rich bouquet of integrated features like Analytics, Exception Notifications etc? If gaining knowledge about design of a good software product interests you, do join us for this interactive session.

1. Let’s build a
Ruby Application Server
Team WebROaR
vineet.tyagi@webroar.in

2. How do ‘you’ visualize an ‘Application Server’?

4. Or it could be like this …

6. Let’s define the specs

7. Rack Compliant
Run all Ruby Web Applications

8. And also ..
 Provide run time performance numbers of
the deployed applications
 Report exceptions

9. Love to have …
 Maximum performance
 Simplicity

10. Let’s start building it …

12. What does the server need to do?
Accept client connection
Parse HTTP request
Hand it over to the ruby web framework
Send its response back to the client

13. Network Server Design
Evented vs Threaded

14. Event Based I/O Libraries
 libev (Written in C)
 EventMachine (Ruby Module + Extension
Library written in C++)

15. HTTP Parser
Mongrel’s Ragel Based Parser (written in C)
is ‘awesome’

16. Server Tasks Options
Accept client connection libev/EventMachine
Parse HTTP request Mongrel’s Ragel based Parser
Hand it over to the ruby web ?
framework
Send its response back to the libev/EventMachine
client

17. More awesomeness - Libebb
 Lightweight HTTP Library for C
 libev + Mongrel’s Ragel based Parser
 Implements HTTP/1.1 Grammar
 Supports persistent, pipelined & chunked requests
 Rejects invalid and malicious requests

18. Server Tasks Options
Accept client connection libebb
Parse HTTP request libebb
Hand it over to the ruby web ?
framework
Send its response back to the libebb
client

19. Embedded Ruby Interpreter
#include <ruby.h>
int main(int argc, char **argv) {
int state = 0;
ruby_init();
ruby_script("c-executable-name");
ruby_init_loadpath();
//Can use rb_gv_set() or rb_iv_set() methods to pass parameters to ruby land
rb_protect(RUBY_METHOD_FUNC(rb_require), (VALUE)"path-to-ruby-script",
&state);
if(state != 0) {
// Exception Handling Code
return -1;
}
//Can use rub_funcall() to invoke methods in the ruby land
return 0;
}

20. Server Tasks Options
Accept client connection libebb
Parse HTTP request libebb
Hand it over to the ruby web Embedded Ruby Interpreter
framework
Send its response back to the libebb
client

21. Hola, we got a basic application server ready!

23. The Server – First Cut
HTTP Request
Rack Web Application
libebb
Ruby Interpreter
Response

24. But it only processes one request at a time ..

25. Let’s split up the server code and create more
ruby processing instances & static file
renderers (‘workers’)

26. The more powerful server version …
Rack Web Application
libev
Asynchronous
Ruby Interpreter
Non-blocking I/O
Worker #1
HTTP Request
Rack Web Application
SCGI libev
libebb libev
Ruby Interpreter
Response
Worker #2
Head
libev Static Files Renderer
Worker #n

28. Server can handle (very) high load with this
architecture

30. Let’s capture data for each request being
processed …

31. The Server – Current Architecture
Message Queue
Analyzer
Admin Panel Daemon
DB Request Analytics Data &
Exception Notifications
Conf File
HTTP Request Worker #1
Head
Worker #n
Response

32. Hurray, we can write all the new advanced
features in our favorite language .. 

33. Ruby makes life easier for …
 Instrumentation
 Messaging
 Analyzer
 Interacting with the Database
 Admin Panel (It’s a Rails Application!)

36. Takeaways
 Use the best tool for the job
 C – Network I/O, Ruby – Advanced Features
 Do not reinvent the wheel. Use tried and
tested libraries

37. Check it out
WebROaR – http://webroar.in

39. Photo Credits
All photographs used in this presentation are
licensed under Creative Commons
 Slide 3 – Stone House By Jsome1
 Slide 5, 34 – Our House By Lee Coursey
 Slide 11 – Willow Lane Construction By Lee Coursey
 Slide 22 – Construction of our House – Framing By
Lee Coursey
 Slide 27 – Dead Lift By scarndp
 Slide 29 – Willow Lane Construction By Lee Coursey
 Slide 35 – Very Happy By Chris Winters
 Slide 38 – Lion By auburnxc

40. More Questions?