The document provides an introduction to the Merb web framework, which is similar to Ruby on Rails but aims to be lighter, more extensible, and faster. It discusses Merb's ideology of keeping the core small and code simple. Key components like routing, views, and plugins are described. Performance tests show Merb using less memory than Rails but slower response times. The author concludes Merb may be worth considering for small tools or limited memory apps, but issues remain with speed on JRuby.

1. Merb, not rails? !
A practical introduction to a new framework.

2. Intro to merb

3. What is merb?
• MVC Framework.
• Similar to Rails.
• Lightweight, extensible, fast.

4. Merb Ideology
• Hacker-friendly.
• Core should be small, plugins bountiful.
• Code should be as simple as possible.
• Code should not be “magical.”

5. Merb is like rails
• Application structure is very similar
• Can use ActiveRecord

6. What does merb-core include?
• rack-based request handling
• session handling
• before / after filters
• layouts / views with erb
• routing

7. What does merb-core include?
• gem-based plugins
• mailers
• partials
• exceptions
• generator for controllers, and models
(integrates with your chosen ORM).

8. What is elsewhere?
• an ORM (can use ActiveRecord,
DataMapper, Sequel)
• form helpers such as form_for
(merb_helper)
• ActiveSupport and all those little ruby
extensions (extlib?)

9. What is elsewhere?
• flash (merb_has_flash and
redirect :message)
• redirect(quot;/posts/34quot;, :message =>
{ :notice => 'Post updated successfully!' })
• scaffolding
• caching (merb-cache)
• ajax library (merb_jquery)

10. DataMapper
• Thread-safe.
• Supports data stores you don’t manage.
• Optimizations in eager-loading, lazy-loading,
etc.

11. What do we need
helper functions for?
• Why not just use HTML for templating
instead of all those helper functions?
• Why not just use JQuery for AJAX instead
of all those AJAX helper functions?

12. Thread-safety
• Merb is thread-safe now.
• Rails will be thread-safe in 2.2.
• What does that mean? http://
blog.headius.com/2008/08/qa-what-thread-
safe-rails-means.html

13. Considerations
• Does your app block?
• File uploads
• Remote HTTP calls
• Facebook app: 1-2s wait time?
• Do you have native threads?
• JRuby / C ruby differences

14. Instances Required
Merb Rails
C MRI, one core, no blocking 1 1
C MRI, one core, 80% blocking 1 5
C MRI, two cores, no blocking 2 2
C MRI, two core, 80% blocking 2 10
Jruby, one core, no blocking 1 1
Jruby, one core, 80% blocking 1 5
Jruby, two cores, no blocking 1 2
Jruby, two core, 80% blocking 1 10
Jruby, 16 cores, 80% blocking 1 80

16. Case study

17. The Project
• CMS for Faculty.
• Keeps track of courses, education,
biography info, etc.
• Deployed to Tomcat.

18. Requirements
• 2500 faculty websites.
• 5 concurrent backend users.
• 500 users per day on the public facing
pages.

19. Can Rails handle that?
• One process per file upload?
• RAM requirements?

20. Why merb?
• Thread-safe.
• Low memory footprint.
• ???

21. Why JRuby?
• Authentication integration using JRadius
• Java platform lowers IT stress level.

22. What is development
like?
• There are no books... yet.
• The codebase is changing.
• Smaller userbase than rails.
• If you are doing anything weird, be prepared
to corepatch!

23. Problems
• File upload broken in Tomcat deploy.
• Partial behavior is totally weird.
• Render syntax changed / broke export
code.
• Activerecord-jdbc mysql quote error.
• String concurrency problem??

24. Other Issues
• acts_as_list had to be extracted from
ActiveRecord files and manually included in
init.rb.

25. Post-mortem

26. Speed Comparison
• Test with simple merb / rails apps using ActiveRecord
• Tests using ab -n 10000
• Testing serially, not concurrently.
• Tested on this MacBook Pro

27. C MRI Mongrel
• Merb: 170 requests / second
• Rails: 32 requests / second

28. JRuby Tomcat
• Merb: 69 requests / second
• Rails : 121 requests / second

29. JRuby Mongrel
• Merb: 104 requests / second
• Rails: 29 requests / second

30. JRuby Glassfish
• Merb: 106 requests / second
• Rails : 125 requests / second

31. What is the deal?
• JRuby thread pool, instead of thread
instantiation?
• Default session handling?
• Overspinning threads in app server?
• Incorrect JIT compilation?

32. Tomcat Memory Usage
• Merb: ~30 MB for all threads
• Rails: ~60 MB+ additional memory per
process
• (Tested on Tomcat)

33. Was it worth it?
• Thread-safety is a minor advantage when it
comes to file uploads.
• Merb uses less memory.
• Merb is slower than rails.
• Merb may die on string thread-safe bug
until JRuby / Merb team fix it.

34. Conclusion

35. Consider merb if...
• you’re writing a small tool.
• you have limited memory requirements.
• you like trying new ORMs.
• you need fast performance (and you’ve
figured out why it runs so slow on JRuby).
• you like hacking about in frameworks.

36. Upcoming
• Merb 1.0 is released Oct 11-12.
• MerbCamp is in San Diego Oct 11-12.
• Merb in Action book (2009?).

37. Available
• I’m available for contracts again. Talk to me
here, at 408-646-2240 or
paulboone@mindbucket.com.
• http://www.mindbucket.com/