Technovangelism

Why won’t Apple make a tablet that is just like a bigger iPod Touch? Ask Steve Ballmer. The experience for developing for the iPhone is so awesome compared to other phones because there is only one screen size and resolution. Removing that part of the equation will place the iPhone on par with its Android and Blackberry competitors. One screen size across every device isn’t the only competitive advantage the iPhone and iPod Touch have, but is it worth it to find out exactly how important it is?

At JavaOne this year, a new design tool (similar to Expression Blend) for JavaFX was demoed and the developer showed off how easily you could change the view to match several different cell phone or desktop resolutions. I could feel the groaning as other developers in the room began to imagine themselves trying to develop like this. It looked like one of the most painful experiences possible (yes, even worse than making your site look perfect in IE6). I’m sure Apple could come up with some fantastic design tool that would be the best multi-resolution design tool in the market. It might even make life easier, or should I say “less difficult,” but it won’t fix the underlying problem.

Don’t expect to see the rumored tablet unless it runs normal OS X. Apple has made enough poor decisions already (with the App Store at least), that it doesn’t need to make any more and ruin a great development experience.

I have wanted to add a “Who’s Online” feature to my forum site for quite some time. Users are more likely to stay and post if they know someone else is there to read what they write. In the first implementation of the site, back in the Rails 1.2 days, sessions were most easily stored in the database with the ActiveRecord SessionStore. This made fetching who is currently using the site easy as all of the necessary information was stored in the database.

Once Rails 2.0 came out, the default session store was using browser cookies. Now it was not so trivial to determine who is on the site. One option was to add a new column to the User model and update it every time the user accessed a page. While this would work, it would mean an extra SQL read and update for every page accessed. The server would have no trouble handling the extra load, but I decided to wait for a better option.

Having not seen a better option in the latest releases of Rails, I implemented my own solution and got my first experience with memcached along the way.

First things first, get memcached installed and running in verbose mode for development:

sudo port install memcached
memcached -vv

Next, set the Rails development environment (in development.rb) to use caching and memcached as the cache store:

config.action_controller.perform_caching = true
config.cache_store = :mem_cache_store

The real work is done by a method in application_controller.rb

before_filter :set_online_users

def set_online_users
  return unless logged_in?

  current_user.last_seen = Time.now
  users = Rails.cache.fetch("online_users") { [current_user] }
  @online_users = users.collect do |user|
    user if user.last_seen > 5.minutes.ago
  end.compact
  unless @online_users.include?(current_user)
    @online_users << current_user
  end
  Rails.cache.write("online_users", @online_users)
end

The final solution is a fast (not verified by benchmarking) solution with zero extra database access. Some readers might notice this is not a thread-safe solution. All lines between the fetch and the write call should be wrapped with a mutex of some sort, but I will leave that for another time.

If you the looking for extra reading, especially about memcached, Railslab: Epsiode 8 is an excellent resource for getting started with memcached and Rails.

The full web interface for HappierHour has been improving from month to month, but with the summer came significantly more “usability testing” from mobile phones. From the start, we tested on phones to ensure the interface would be mostly usable, but it is time to make a first-class mobile interface.

Look for a release in the coming weeks that will include the new interface. If anything looks off or you want to request a mobile-specific feature, leave a comment.