Debugging toolbar for Rack applications implemented as middleware
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Rack::Insight began life as an fork of Logical::Insight by LRDesign.

  • I started a fork because:
    • LogicalInsight was namespaced as "Insight"
      • Causing namespace collisions everywhere I have an Insight model. I had to re-namespace all the code.
    • I also needed to build a few extension gems with additional panels, which didn't fully work in LI
      • Added the Config class to allow for custom panel load paths and many other extensions that don't work in the use Middleware declaration.

It should be even easier to extend than LogicalInsight was, because extension gems can access the Config class and truly bolt-on cleanly.

Having made really significant architectural changes, I'll be keeping Rack::Insight a separate project for the foreseeable future.


Rack::Insight adds a diagnostics toolbar to Rack apps. When enabled, it injects a floating div allowing exploration of logging, database queries, template rendering times, etc. Rack::Insight stores debugging info over many requests, incuding AJAX requests.


  • Password-based security
  • IP-based security
  • Rack::Insight instrumentation/reporting is broken up into panels.
    • Panels in default configuration:
      • Rails Info
      • Timer
      • Request Variables
      • Cache
      • Templates
      • Log (can configure which loggers to watch!)
      • Memory
      • SQL (Failing specs, and I don't use it, someone please pull me a fix!)
      • Active Record (Failing specs, and I don't use it, someone please pull me a fix!)
    • Other bundled panels:
      • Redis
      • Speedtracer
    • Retired panels - if needed they could come back quickly:
      • Sphinx
      • Mongo
    • The API for adding your own panels is simple and very powerful
      • Consistent interface to instrument application code
      • Consistent timing across panels
      • Easy to add sub-applications for more detailed reports (c.f. SQLPanel)
      • Ask me (pboling) if you need help with this.

Rails quick start

Add this to your Gemfile gem "rack-insight"

In config/environments/development.rb, add:

config.middleware.use "Rack::Insight::App",
  :secret_key => "someverylongandveryhardtoguesspreferablyrandomstring"

Any environment with Rack::Insight loaded will have a link to "Rack::Insight" added to as the last child of BODY to normal responses. Clicking that link will load the toolbar. It's set with an id of "rack-insight-enabler", so it can be styled to go somewhere more noticeable. E.g. "position: absolute; top: 0; left: 0"

Using with non-Rails Rack apps

Just 'use Rack::Insight' as any other middleware. See the SampleApp in the spec/fixtures folder for an example Sinatra app.

If you wish to use the logger panel define the LOGGER constant that is a ruby Logger or ActiveSupport::BufferedLogger

Configure Rack::Insight


Rack::Insight::Config.configure do |config|
  config[:option] = value


:logger - Can be set to any Ruby-esque Logger, examples include the Rails Logger, or the Ruby Logger (default).
        If you do not set logger Rack::Insight defaults to the Ruby Logger.
        You can configure it with additional options:
        :log_file - The logdev parameter for the Ruby Logger (a file path, an IO, like STDOUT, or STDERR, etc)
        :log_level - The maximum severity at which things should be logged.

:rails_log_copy - If you are setting :logger to the Rails Logger, you should set this to false (default is true).

:verbosity - true is default .
           true is equivalent to relying soley on the logger's log level to determine if a message is logged.
           Other potential values are:
              anything falsey => no logging at all
              Rack::Insight::Logging::VERBOSITY[*level*] where *level* is one of:
                :debug, :high, :med, :low, :silent

:panel_load_paths => [File::join('rack', 'insight', 'panels')] (default)
                     See *Configuring custom panels* section for example usage

:panel_configs => This is a nested config, se below:

  Panel level configuration options for all panels, including extension gems.
  Currently this is implemented in the log_panel, and configured as:

    Rack::Insight::Config.configure do |config|
      # The following two lines have the same result
      config[:panel_configs][:log] = {:probes => {'Logger' => [:instance, :add]}}
      config[:panel_configs][:log] = {:probes => ['Logger', :instance, :add]}

  Example:  If you want all of your log statements in Rails to be traced twice by Rack::Insight,
            this will do that because ActiveSupport::BufferedLogger utilizes Logger under the hood:

    config[:panel_configs][:log_panel] = {:probes => {
            "ActiveSupport::BufferedLogger" => [:instance, :add],
            "Logger" => [:instance, :add]

:database => a hash.  Keys :raise_encoding_errors, and :raise_decoding_errors are self explanatory
                 When set to true, if there is an encoding error (unlikely)
                 it will cause a 500 error on your site.  !!!WARNING!!!
                 The bundled panels should work fine with :raise_decoding_errors set to true or false
                 but custom panel implementations may prefer one over the other
                 The bundled panels will capture these errors and perform admirably.
                 Site won't go down unless a custom panel is not handling the errors well.

Configure Middleware

Specify the set of panels you want, in the order you want them to appear:

require "rack-insight"

ActionController::Dispatcher.middleware.use "Rack::Insight::App",
  :secret_key => "someverylongandveryhardtoguesspreferablyrandomstring",
  :panel_files => %w[

By default panel files are looked up by prepending "rack/insight/panels/" and requiring them. Subclasses of Rack::Insight::Panel are loaded and added to the toolbar. This makes it easier to work with the configuration and extend Rack::Insight with plugin gems.

If you need to customize the load paths where Rack::Insight will look for panels you can configure the load paths in an initializer, or in your gem prior to requiring your panels. Example config/initializers/rack_insight.rb:

Rack::Insight::Config.configure do |config|

  # Note: The parent directory of the 'special' directory must already be in Ruby's load path.
  config[:panel_load_paths] = File.join('special','path')

  # Example 1: Do not load any of the regular Rack::Insight panels:
  config[:panel_load_paths] = File.join('my','custom','panel','directory')

  # Example 2: Add your custom path to the existing load paths, to have your panels join the party!
  config[:panel_load_paths] << 'custom/panels'


When you create custom panels use the render_template method and pass it the path to the view to be rendered relative to the panel load path you added above:

# with Example #2 from above, will try to render 'custom/panels/thunder_panel/views/thor.html.erb'
render_template 'thunder_panel/views/thor'

Running Rack::Insight in staging or production

We have have found that Rack::Insight is fast enough to run in production for specific troubleshooting efforts.


Add the middleware configuration to an initializer or the appropriate environment files, taking the rest of this section into consideration.


Restrict access to particular IP addresses:

require "ipaddr"

ActionController::Dispatcher.middleware.use "Rack::Insight::App"
  :secret_key => "someverylongandveryhardtoguesspreferablyrandomstring",
  :ip_masks   => ["")]

Restrict access using a password:

ActionController::Dispatcher.middleware.use "Rack::Insight::App",
  :secret_key => "someverylongandveryhardtoguesspreferablyrandomstring",
  :ip_masks   => false # Default is
  :password   => "yourpassword"

custom file path for the request recording database

Logical Rack::Insight uses SQLite to store data from requests, and outputs a database file in the root directory. If you need the file to be created at another location (i.e. Heroku), you can pass a custom file path.

ActionController::Dispatcher.middleware.use "Rack::Insight::App"
  :secret_key => "someverylongandveryhardtoguesspreferablyrandomstring",
  :database_path => "tmp/my_insight_db.sqlite"

Magic Panels

You can now create a fully functional new panel with a simple class definition:

module Rack::Insight
  class FooBarPanel < Panel
    self.is_magic = true

Setup the probes for the magic panel in a before_initialize block in your application.rb as follows:

# Assuming there is a FooBra class with instance methods: foo, bar, cheese, and ducks
Rack::Insight::Config.configure do |config|
  # Not :foo_bar_panel or 'FooBarPanel'... :foo_bar
  config[:panel_configs][:foo_bar] = {:probes => {'FooBra' => [:instance, :foo, :bar, :cheese, :ducks]}}

Custom Panels

See Magic Panels above, remove teh is_magic declaration, and add your own methods. Look at the panels bundled with this gem for pointers. Here are some important methods to watch for:

  • initialize
  • after_detect
  • content_for_request(number)


  • Maintained by Peter Boling
  • Based on LogicalInsight by Judson Lester
    • Contributions from Luke Melia, Joey Aghion, Tim Connor, and more
    • Which in turn was based on Rack::Bug by Bryan Helmkamp


Rack::Insight owes a lot to both LogicalInsight and Rack::Bug, as the basis projects. There's a lot of smart in there. Many thanks to Evan, Judson, and Bryan for building them.

Inspiration for Rack::Bug is primarily from the Django debug toolbar. Additional ideas from Rails footnotes, Rack's ShowException middleware, Oink, and Rack::Cache


MIT. See LICENSE in this directory.


Legacy files: would like to re-include them, but they need work



This one is mostly just a curiosity lib/rack/insight/panels/speedtracer_panel/profiling.rb