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Profiler for your development and production Ruby rack apps.
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Middleware that displays speed badge for every html page. Designed to work both in production and in development.


  • Database profiling - Currently supports Mysql2, Postgres, Oracle (oracle_enhanced ~> 1.5.0) and Mongoid3 (with fallback support to ActiveRecord)
  • Call-stack profiling - Flame graphs showing time spent by gem
  • Memory profiling - Per-request memory usage, GC stats, and global allocation metrics

Learn more

rack-mini-profiler needs your help

We have decided to restructure our repository so there is a central UI repo and the various language implementations have their own.


If you feel like taking on any of this start an issue and update us on your progress.


Install/add to Gemfile in Ruby 2.3+

gem 'rack-mini-profiler'

NOTE: Be sure to require rack_mini_profiler below the pg and mysql gems in your Gemfile. rack_mini_profiler will identify these gems if they are loaded to insert instrumentation. If included too early no SQL will show up.

You can also include optional libraries to enable additional features.

# For memory profiling
gem 'memory_profiler'

# For call-stack profiling flamegraphs
gem 'flamegraph'
gem 'stackprof'


All you have to do is to include the Gem and you're good to go in development. See notes below for use in production.

Upgrading to version 2.0.0

Prior to version 2.0.0, Mini Profiler patched various Rails methods to get the information it needed such as template rendering time. Starting from version 2.0.0, Mini Profiler doesn't patch any Rails methods by default and relies on ActiveSupport::Notifications to get the information it needs from Rails. If you want Mini Profiler to keep using its patches in version 2.0.0 and later, change the gem line in your Gemfile to the following:

If you want to manually require Mini Profiler:

gem 'rack-mini-profiler', require: ['enable_rails_patches']

If you don't want to manually require Mini Profiler:

gem 'rack-mini-profiler', require: ['enable_rails_patches', 'rack-mini-profiler']

Rails and manual initialization

In case you need to make sure rack_mini_profiler is initialized after all other gems, or you want to execute some code before rack_mini_profiler required:

gem 'rack-mini-profiler', require: false

Note the require: false part - if omitted, it will cause the Railtie for the mini-profiler to be loaded outright, and an attempt to re-initialize it manually will raise an exception.

Then run the generator which will set up rack-mini-profiler in development:

bundle exec rails g rack_profiler:install

Rack Builder

require 'rack-mini-profiler'

home = lambda { |env|
  [200, {'Content-Type' => 'text/html'}, ["<html><body>hello!</body></html>"]]

builder = do
  use Rack::MiniProfiler
  map('/') { run home }

run builder


require 'rack-mini-profiler'
class MyApp < Sinatra::Base
  use Rack::MiniProfiler


For working with hanami, you need to use rack integration. Also, you need to add Hanami::View::Rendering::Partial#render method for profile:

require 'rack-mini-profiler'
Rack::MiniProfiler.profile_method(Hanami::View::Rendering::Partial, :render) { "Render partial #{@options[:partial]}" }

use Rack::MiniProfiler

Patching ActiveRecord

A typical web application spends a lot of time querying the database. rack_mini_profiler will detect the ORM that is available and apply patches to properly collect query statistics.

To make this work, declare the orm's gem before declaring rack-mini-profiler in the Gemfile:

gem 'pg'
gem 'mongoid'
gem 'rack-mini-profiler'

If you wish to override this behavior, the environment variable RACK_MINI_PROFILER_PATCH is available.

export RACK_MINI_PROFILER_PATCH="pg,mongoid"
# or
# initializers/rack_profiler.rb: SqlPatches.patch %w(mongo)


To generate flamegraphs:

  • add the flamegraph gem to your Gemfile
  • visit a page in your app with ?pp=flamegraph

Memory Profiling

Memory allocations can be measured (using the memory_profiler gem) which will show allocations broken down by gem, file location, and class and will also highlight String allocations.

Add ?pp=profile-memory to the URL of any request while Rack::MiniProfiler is enabled to generate the report.

Additional query parameters can be used to filter the results.

  • memory_profiler_allow_files - filename pattern to include (default is all files)
  • memory_profiler_ignore_files - filename pattern to exclude (default is no exclusions)
  • memory_profiler_top - number of results per section (defaults to 50)

The allow/ignore patterns will be treated as regular expressions.

Example: ?pp=profile-memory&memory_profiler_allow_files=active_record|app

There are two additional pp options that can be used to analyze memory which do not require the memory_profiler gem

  • Use ?pp=profile-gc to report on Garbage Collection statistics
  • Use ?pp=analyze-memory to report on ObjectSpace statistics

Access control in non-development environments

rack-mini-profiler is designed with production profiling in mind. To enable that run Rack::MiniProfiler.authorize_request once you know a request is allowed to profile.

  # inside your ApplicationController

  before_action do
    if current_user && current_user.is_admin?

If your production application is running on more than one server (or more than one dyno) you will need to configure rack mini profiler's storage to use Redis or Memcache. See storage for information on changing the storage backend.


Out-of-the-box we will initialize the authorization_mode to :whitelist in production. However, in some cases we may not be able to do it:

  • If you are running in development or test we will not enable whitelist mode
  • If you use require: false on rack_mini_profiler we are unlikely to be able to run the railtie
  • If you are running outside of rails we will not run the railtie

In those cases use:

Rack::MiniProfiler.config.authorization_mode = :whitelist

When deciding to fully profile a page mini profiler consults with the authorization_mode

By default in production we attempt to set the authorization mode to :whitelist meaning that end user will only be able to see requests where somewhere Rack::MiniProfiler.authorize_request is invoked.

In development we run in the :allow_all authorization mode meaning every request is profiled and displayed to the end user.


Various aspects of rack-mini-profiler's behavior can be configured when your app boots. For example in a Rails app, this should be done in an initializer: config/initializers/mini_profiler.rb

Caching behavior

To fix some nasty bugs with rack-mini-profiler showing the wrong data, the middleware will remove headers relating to caching (Date & Etag on responses, If-Modified-Since & If-None-Match on requests). This probably won't ever break your application, but it can cause some unexpected behavior. For example, in a Rails app, calls to stale? will always return true.

To disable this behavior, use the following config setting:

# Do not let rack-mini-profiler disable caching
Rack::MiniProfiler.config.disable_caching = false # defaults to true


rack-mini-profiler stores its results so they can be shared later and aren't lost at the end of the request.

There are 4 storage options: MemoryStore, RedisStore, MemcacheStore, and FileStore.

FileStore is the default in Rails environments and will write files to tmp/miniprofiler/*. MemoryStore is the default otherwise.

# set MemoryStore = Rack::MiniProfiler::MemoryStore

# set RedisStore
if Rails.env.production?
  Rack::MiniProfiler.config.storage_options = { url: ENV["REDIS_SERVER_URL"] } = Rack::MiniProfiler::RedisStore

MemoryStore stores results in a processes heap - something that does not work well in a multi process environment. FileStore stores results in the file system - something that may not work well in a multi machine environment. RedisStore/MemcacheStore work in multi process and multi machine environments (RedisStore only saves results for up to 24 hours so it won't continue to fill up Redis). You will need to add gem redis/gem dalli respectively to your Gemfile to use these stores.

Additionally you may implement an AbstractStore for your own provider.

User result segregation

MiniProfiler will attempt to keep all user results isolated, out-of-the-box the user provider uses the ip address:

Rack::MiniProfiler.config.user_provider ={|env|}

You can override (something that is very important in a multi-machine production setup):

Rack::MiniProfiler.config.user_provider ={ |env| CurrentUser.get(env) }

The string this function returns should be unique for each user on the system (for anonymous you may need to fall back to ip address)

Profiling specific methods

You can increase the granularity of profiling by measuring the performance of specific methods. Add methods of interest to an initializer.

Rails.application.config.to_prepare do
  ::Rack::MiniProfiler.profile_singleton_method(User, :non_admins) { |a| "executing all_non_admins" }
  ::Rack::MiniProfiler.profile_method(User, :favorite_post) { |a| "executing favorite_post" }

Profiling arbitrary block of code

It is also possible to profile any arbitrary block of code by passing a block to Rack::MiniProfiler.step(name, opts=nil).

Rack::MiniProfiler.step('Adding two elements') do
  result = 1 + 2

Using in SPA applications

Single page applications built using Ember, Angular or other frameworks need some special care, as routes often change without a full page load.

On route transition always call:


This method will remove profiling information that was related to previous page and clear aggregate statistics.

MiniProfiler's speed badge on pages that are not generated via Rails

You need to inject the following in your SPA to load MiniProfiler's speed badge (extra details surrounding this script):

 <script async type="text/javascript" id="mini-profiler" src="/mini-profiler-resources/includes.js?v=12b4b45a3c42e6e15503d7a03810ff33" data-version="12b4b45a3c42e6e15503d7a03810ff33" data-path="/mini-profiler-resources/" data-current-id="redo66j4g1077kto8uh3" data-ids="redo66j4g1077kto8uh3" data-horizontal-position="left" data-vertical-position="top" data-trivial="false" data-children="false" data-max-traces="10" data-controls="false" data-authorized="true" data-toggle-shortcut="Alt+P" data-start-hidden="false" data-collapse-results="true"></script>

Note: The GUID (data-version and the ?v= parameter on the src) will change with each release of rack_mini_profiler. The MiniProfiler's speed badge will continue to work, although you will have to change the GUID to expire the script to fetch the most recent version.

Using MiniProfiler's built in route for apps without HTML responses

MiniProfiler also ships with a /rack-mini-profiler/requests route that displays the speed badge on a blank HTML page. This can be useful when profiling an application that does not render HTML.

Configuration Options

You can set configuration options using the configuration accessor on Rack::MiniProfiler. For example:

Rack::MiniProfiler.config.position = 'bottom-right'
Rack::MiniProfiler.config.start_hidden = true

The available configuration options are:

Option Default Description
pre_authorize_cb Rails: dev only
Rack: always on
A lambda callback that returns true to make mini_profiler visible on a given request.
position 'top-left' Display mini_profiler on 'top-right', 'top-left', 'bottom-right' or 'bottom-left'.
skip_paths [] Paths that skip profiling.
skip_schema_queries Rails dev: 'true'
Othwerwise: 'false'
'true' to log schema queries.
auto_inject true true to inject the miniprofiler script in the page.
backtrace_ignores [] Regexes of lines to be removed from backtraces.
backtrace_includes Rails: [/^\/?(app|config|lib|test)/]
Rack: []
Regexes of lines to keep in backtraces.
backtrace_remove rails: Rails.root
Rack: nil
A string or regex to remove part of each line in the backtrace.
toggle_shortcut Alt+P Keyboard shortcut to toggle the mini_profiler's visibility. See jquery.hotkeys.
start_hidden false false to make mini_profiler visible on page load.
backtrace_threshold_ms 0 Minimum SQL query elapsed time before a backtrace is recorded.
flamegraph_sample_rate 0.5 How often to capture stack traces for flamegraphs in milliseconds.
base_url_path '/mini-profiler-resources/' Path for assets; added as a prefix when naming assets and sought when responding to requests.
collapse_results true If multiple timing results exist in a single page, collapse them till clicked.
max_traces_to_show 20 Maximum number of mini profiler timing blocks to show on one page
html_container body The HTML container (as a jQuery selector) to inject the mini_profiler UI into
show_total_sql_count false Displays the total number of SQL executions.
enable_advanced_debugging_tools false Enables sensitive debugging tools that can be used via the UI. In production we recommend keeping this disabled as memory and environment debugging tools can expose contents of memory that may contain passwords.

Custom middleware ordering (required if using Rack::Deflate with Rails)

If you are using Rack::Deflate with rails and rack-mini-profiler in its default configuration, Rack::MiniProfiler will be injected (as always) at position 0 in the middleware stack. This will result in it attempting to inject html into the already-compressed response body. To fix this, the middleware ordering must be overriden.

To do this, first add , require: false to the gemfile entry for rack-mini-profiler. This will prevent the railtie from running. Then, customize the initialization in the initializer like so:

require 'rack-mini-profiler'


Rails.application.middleware.insert_after(Rack::Deflater, Rack::MiniProfiler)

Deleting the middleware and then reinserting it is a bit inelegant, but a sufficient and costless solution. It is possible that rack-mini-profiler might support this scenario more directly if it is found that there is significant need for this confriguration or that the above recipe causes problems.

Special query strings

If you include the query string pp=help at the end of your request you will see the various options available. You can use these options to extend or contract the amount of diagnostics rack-mini-profiler gathers.

Rails 2.X support

To get MiniProfiler working with Rails 2.3.X you need to do the initialization manually as well as monkey patch away an incompatibility between activesupport and json_pure.

Add the following code to your environment.rb (or just in a specific environment such as development.rb) for initialization and configuration of MiniProfiler.

# configure and initialize MiniProfiler
require 'rack-mini-profiler'
c = ::Rack::MiniProfiler.config
c.pre_authorize_cb = lambda { |env|
  Rails.env.development? || Rails.env.production?
tmp = Rails.root.to_s + "/tmp/miniprofiler"
FileUtils.mkdir_p(tmp) unless File.exist?(tmp)
c.storage_options = {:path => tmp} = ::Rack::MiniProfiler::FileStore
::Rack::MiniProfiler.profile_method(ActionController::Base, :process) {|action| "Executing action: #{action}"}
::Rack::MiniProfiler.profile_method(ActionView::Template, :render) {|x,y| "Rendering: #{path_without_format_and_extension}"}

# monkey patch away an activesupport and json_pure incompatability
if JSON.const_defined?(:Pure)
  class JSON::Pure::Generator::State
    include ActiveSupport::CoreExtensions::Hash::Except

Running the Specs

$ rake build
$ rake spec

Additionally you can also run autotest if you like.


The MIT License (MIT)

Copyright (c) 2013 Sam Saffron

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.


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