It’s up at github – installation is dead easy (assuming you’re on Rails 2.3+, of course) – just install the plugin, restart your app, and hit <your url>/stats/scrap in your browser. Bam, instant juicy memory goodness about your app at your fingertips. If you’d like an example of the output, good news! Check it out at http://tachyonsix.com/scrap.htm.

You can use it to troubleshoot heap leaks – just run a few requests, hit your Scrap URL, and see what your deltas look like. Seeing a huge growth in a certain type of object? Chances are pretty good that you have a heap leak, and can start tracking it down.

The request history can help you locate certain actions that might be causing spikes in memory usage. It’ll show the last N requests, along with memory and heap statistics before each request. If there’s a consistent memory usage leap after a certain action, chances are that it’s doing something naughty.

Want to get a bigger picture on what objects are hanging around? You can use the config/scrap.yml file to get Scrap to spit out more detailed reports on instances of a given class. There’s full documentation on it in the README.

Anyhow, give it a shot, let me know what you think.

It’s definitely worth a look, especially if you’re running in a complex environment, where new closures will be large and unwieldy. It’s very easy, too. Any time you use:

def note(text, options = {}, &block)
  options[:class] = ((options[:class] || "") + " form-note").strip
  content_tag(:div, text, options, &block)
end

Instead, don’t explicitly name the block parameter; just yield to it, and you prevent all the messiness of creating a new Proc object.

def note(text, options = {})
  options[:class] = ((options[:class] || "") + " form-note").strip
  content_tag(:div, text, options) {|*block_args| yield(*block_args) if block_given? }
end

I don’t have benchmarks just yet, but anecdotally it has definitely slowed instance memory consumption in my apps. It’s worth taking a look at!