asemanfar - a blog about programming

The CodeRack Contest recently came to a close and RackProctitle came in 3rd place.

RackProctitle allows you to see what request a given web server process is handling. By running "watch -n 0.1 ‘ps aux | grep “USER\|rack” ’ you can see all your rack processes, what request each is currently handling and for how long (or if they’re idle), what their last request was and how long it took, how many requests have been handled in the life of this process, and the requests in queue (if it's receiving more than 1 request at a time).

It ends up being really useful to diagnose problems. Example output [screenshot]:

   1  rack/14a0b0 [1/682]: handling 0.0s /users/6014086

You can set a prefix, which will replace “rack” in the line above, and you can set an APPLICATION_VERSION constant which will be after the prefix. You can use this to distinguish between different rack processes if you run multiple applications on the same machine. In the example above, APPLICATION_VERSION is set to the first six characters of the git commit hash.

It's a gem:

   1  sudo gem install rack_proctitle

In some file somewhere in your application (optional):

   1  APPLICATION_VERSION = File.read(File.join(RAILS_ROOT, “REVISION”))[0,6] # if you use Capistrano, which creates a REVISION file for you.

In your rackup file (prefix is optional):

   1  use RackProctitle, :prefix => “application_name”

We use watch to get a continuously updating status of our rack processes:

   1  watch -n 0.1 ‘ps aux | grep “USER\|application_name” | grep -v grep ; uptime; hostname’

The watch linux utility is one of those things that is hard to Google, so here's the link if it's not installed or not in your package manager: http://procps.sourceforge.net/

Concept and output formatting is based on Alexander Staubo’s mongrel_proctitle but has more features, is thread safe, and is Rack compatible. For more information on why mongrel_proctitle is not thread safe, read this post.

As always, feature requests and bug reports always welcome.