Middleware for profiling Rack-compatible apps using perftools.rb
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Middleware for profiling Rack-compatible apps using perftools.rb (github.com/tmm1/perftools.rb)


You'll need graphviz to generate call graphs using dot (for the GIF printer):

sudo port install graphviz     # OS X
brew install graphviz          # Homebrew
sudo apt-get install graphviz  # Debian/Ubuntu

You'll need ps2pdf to generate PDFs (On OS X, ps2pdf comes is installed as part of Ghostscript)

sudo port install ghostscript  # OSX
brew install ghostscript       # Homebrew
sudo apt-get install ps2pdf    # Debian/Ubuntu


Install the gem

gem install rack-perftools_profiler

Include the middleware

require 'rack/perftools_profiler'

For Rails, add the following to config/environment.rb

config.gem 'rack-perftools_profiler', :version => '~> 0.0.1', :lib => 'rack/perftools_profiler'
require 'rack/perftools_profiler'
config.middleware.use Rack::PerftoolsProfiler, :default_printer => 'gif'

For Sinatra, call 'use' inside a configure block, like so:

configure :profiling do
  use Rack::PerftoolsProfiler, :default_printer => 'gif'

For Rack::Builder, call 'use' inside the Builder constructor block

Rack::Builder.new do
  use Rack::PerftoolsProfiler, :default_printer => 'gif'


  • :bundler - run profiler binary from bundle if set to true

  • :gemfile_dir - directory with Gemfile

  • :default_printer - can be set to 'text', 'gif', or 'pdf'. Default is :text

  • :mode - can be set to 'cputime' or 'walltime'. Default is :cputime

  • :frequency - in :cputime mode, the number of times per second the app will be sampled. Default is 100 (times/sec)


There are two modes for the profiler

First, you can run in 'simple' mode. Just visit the url you want to profile, but add the 'profile' and (optionally) the 'times' GET params (which will rerun the action the specified number of times).


curl http://localhost:8080/foobar?profile=true&times=3

Note that this will change the status, body, and headers of the response (you'll get back the profiling data, NOT the original response).

The other mode is start/stop mode.


curl http://localhost:8080/__start__
curl http://localhost:8080/foobar
curl http://localhost:8080/foobaz
curl http://localhost:8080/__stop__
curl http://localhost:8080/__data__

In this mode, all responses are normal. You must visit __stop__ to complete profiling and then you can view the profiling data by visiting __data__

Profiling Data Options

In both simple and start/stop modes, you can add additional params to change how the data is displayed. In simple mode, these params are just added to the URL being profiled. In start/stop mode, they are added to the __data__ URL

  • printer - overrides the default_printer option (see above)

  • ignore - a regular expression of the area of code to ignore

  • focus - a regular expression of the area of code to solely focus on.

(for 'ignore' and 'focus', please see google-perftools.googlecode.com/svn/trunk/doc/cpuprofile.html#pprof for more details)


A huge thanks to Aman Gupta for the awesome perftools.rb gem.

The basic idea and initial implementation of the middleware was heavily influenced by Rack::Profiler from rack-contrib.

Note on Patches/Pull Requests

  • Fork the project.

  • Make your feature addition or bug fix.

  • Add tests for it. This is important so I don't break it in a future version unintentionally.

  • Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)

  • Send me a pull request. Bonus points for topic branches.


Copyright © 2010 Ben Brinckerhoff. See LICENSE for details.