# Bullet

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The Bullet gem is designed to help you increase your application's performance by reducing the number of queries it makes. It will watch your queries while you develop your application and notify you when you should add eager loading (N+1 queries), when you're using eager loading that isn't necessary and when you should use counter cache.

Best practice is to use Bullet in development mode or custom mode (staging, profile, etc.). The last thing you want is your clients getting alerts about how lazy you are.

Bullet gem now supports **activerecord** >= 4.0 and **mongoid** >= 4.0.

If you use activerecord 2.x, please use bullet <= 4.5.0

If you use activerecord 3.x, please use bullet < 5.5.0

## External Introduction

* [https://rubyonrails.org/2009/10/22/community-highlights](https://rubyonrails.org/2009/10/22/community-highlights)
* [https://www.shakacode.com/blog/eliminate-N-1-queries-with-bullet/](https://www.shakacode.com/blog/eliminate-N-1-queries-with-bullet/)
* [https://reinteractive.com/articles/ruby-on-rails-community/elevating-your-code-quality-bullet-gem-and-query-prevention-in-testing](https://reinteractive.com/articles/ruby-on-rails-community/elevating-your-code-quality-bullet-gem-and-query-prevention-in-testing)

## Install

You can install it as a gem:

```
gem install bullet
```

or add it into a Gemfile (Bundler):


```ruby
gem 'bullet', group: 'development'
```

enable the Bullet gem with generate command

```ruby
bundle exec rails g bullet:install
```
The generate command will auto generate the default configuration and may ask to include in the test environment as well. See below for custom configuration.

**Note**: make sure `bullet` gem is added after activerecord (rails) and
mongoid.

## Configuration

Bullet won't enable any notification systems unless you tell it to explicitly. Append to
`config/environments/development.rb` initializer with the following code:

```ruby
config.after_initialize do
  Bullet.enable = true
  Bullet.sentry = true
  Bullet.alert = true
  Bullet.bullet_logger = true
  Bullet.console = true
  Bullet.xmpp = { :account  => 'bullets_account@jabber.org',
                  :password => 'bullets_password_for_jabber',
                  :receiver => 'your_account@jabber.org',
                  :show_online_status => true }
  Bullet.rails_logger = true
  Bullet.honeybadger = true
  Bullet.bugsnag = true
  Bullet.appsignal = true
  Bullet.airbrake = true
  Bullet.rollbar = true
  Bullet.add_footer = true
  Bullet.skip_html_injection = false
  Bullet.skip_http_headers = false
  Bullet.stacktrace_includes = [ 'your_gem', 'your_middleware' ]
  Bullet.stacktrace_excludes = [ 'their_gem', 'their_middleware', ['my_file.rb', 'my_method'], ['my_file.rb', 16..20] ]
  Bullet.slack = { webhook_url: 'http://some.slack.url', channel: '#default', username: 'notifier' }
  Bullet.opentelemetry = true
  Bullet.raise = false
  Bullet.always_append_html_body = false
  Bullet.skip_user_in_notification = false
end
```

The notifier of Bullet is a wrap of [uniform_notifier](https://github.com/flyerhzm/uniform_notifier)

The code above will enable all of the Bullet notification systems:
* `Bullet.enable`: enable Bullet gem, otherwise do nothing
* `Bullet.sentry`: add notifications to sentry
* `Bullet.alert`: pop up a JavaScript alert in the browser
* `Bullet.bullet_logger`: log to the Bullet log file (Rails.root/log/bullet.log)
* `Bullet.console`: log warnings to your browser's console.log (Safari/Webkit browsers or Firefox w/Firebug installed)
* `Bullet.xmpp`: send XMPP/Jabber notifications to the receiver indicated. Note that the code will currently not handle the adding of contacts, so you will need to make both accounts indicated know each other manually before you will receive any notifications. If you restart the development server frequently, the 'coming online' sound for the Bullet account may start to annoy - in this case set :show_online_status to false; you will still get notifications, but the Bullet account won't announce it's online status anymore.
* `Bullet.rails_logger`: add warnings directly to the Rails log
* `Bullet.honeybadger`: add notifications to Honeybadger
* `Bullet.bugsnag`: add notifications to bugsnag
* `Bullet.appsignal`: add notifications to AppSignal
* `Bullet.airbrake`: add notifications to airbrake
* `Bullet.rollbar`: add notifications to rollbar
* `Bullet.add_footer`: adds the details in the bottom left corner of the page. Double click the footer or use close button to hide footer.
* `Bullet.skip_html_injection`: prevents Bullet from injecting code into the returned HTML. This must be false for receiving alerts, showing the footer or console logging.
* `Bullet.skip_http_headers`: don't add headers to API requests, and remove the javascript that relies on them. Note that this prevents bullet from logging warnings to the browser console or updating the footer.
* `Bullet.stacktrace_includes`: include paths with any of these substrings in the stack trace, even if they are not in your main app
* `Bullet.stacktrace_excludes`: ignore paths with any of these substrings in the stack trace, even if they are not in your main app.
   Each item can be a string (match substring), a regex, or an array where the first item is a path to match, and the second
   item is a line number, a Range of line numbers, or a (bare) method name, to exclude only particular lines in a file.
* `Bullet.slack`: add notifications to slack
* `Bullet.opentelemetry`: add notifications to OpenTelemetry
* `Bullet.raise`: raise errors, useful for making your specs fail unless they have optimized queries
* `Bullet.always_append_html_body`: always append the html body even if no notifications are present. Note: `console` or `add_footer` must also be true. Useful for Single Page Applications where the initial page load might not have any notifications present.
* `Bullet.skip_user_in_notification`: exclude the OS user (`whoami`) from notifications.


Bullet also allows you to disable any of its detectors.

```ruby
# Each of these settings defaults to true

# Detect N+1 queries
Bullet.n_plus_one_query_enable     = false

# Detect eager-loaded associations which are not used
Bullet.unused_eager_loading_enable = false

# Detect unnecessary COUNT queries which could be avoided
# with a counter_cache
Bullet.counter_cache_enable        = false
```

## Safe list

Sometimes Bullet may notify you of query problems you don't care to fix, or
which come from outside your code. You can add them to a safe list to ignore them:

```ruby
Bullet.add_safelist :type => :n_plus_one_query, :class_name => "Post", :association => :comments
Bullet.add_safelist :type => :unused_eager_loading, :class_name => "Post", :association => :comments
Bullet.add_safelist :type => :counter_cache, :class_name => "Country", :association => :cities
```

If you want to skip bullet in some specific controller actions, you can
do like

```ruby
class ApplicationController < ActionController::Base
  around_action :skip_bullet, if: -> { defined?(Bullet) }

  def skip_bullet
    previous_value = Bullet.enable?
    Bullet.enable = false
    yield
  ensure
    Bullet.enable = previous_value
  end
end
```

## Log

The Bullet log `log/bullet.log` will look something like this:

* N+1 Query:

```
2009-08-25 20:40:17[INFO] USE eager loading detected:
  Post => [:comments]·
  Add to your query: .includes([:comments])
2009-08-25 20:40:17[INFO] Call stack
  /Users/richard/Downloads/test/app/views/posts/index.html.erb:8:in `each'
  /Users/richard/Downloads/test/app/controllers/posts_controller.rb:7:in `index'
```

The first log entry is a notification that N+1 queries have been encountered. The remaining entry is a stack trace so you can find exactly where the queries were invoked in your code, and fix them.

* Unused eager loading:

```
2009-08-25 20:53:56[INFO] AVOID eager loading detected
  Post => [:comments]·
  Remove from your query: .includes([:comments])
2009-08-25 20:53:56[INFO] Call stack
```

These lines are notifications that unused eager loadings have been encountered.

* Need counter cache:

```
2009-09-11 09:46:50[INFO] Need Counter Cache
  Post => [:comments]
```

## XMPP/Jabber and Airbrake Support

see [https://github.com/flyerhzm/uniform_notifier](https://github.com/flyerhzm/uniform_notifier)

## Growl Support

Growl support is dropped from uniform_notifier 1.16.0, if you still want it, please use uniform_notifier 1.15.0.

## URL query control

You can add the URL query parameter `skip_html_injection` to make the current HTML request behave as if `Bullet.skip_html_injection` is enabled,
e.g. `http://localhost:3000/posts?skip_html_injection=true`

## Important

If you find Bullet does not work for you, *please disable your browser's cache*.

## Advanced

### Work with ActiveJob

Include `Bullet::ActiveJob` in your `ApplicationJob`.

```ruby
class ApplicationJob < ActiveJob::Base
  include Bullet::ActiveJob if Rails.env.development?
end
```

### Work with other background job solution

Use the Bullet.profile method.

```ruby
class ApplicationJob < ActiveJob::Base
  around_perform do |_job, block|
    Bullet.profile do
      block.call
    end
  end
end
```

### Work with sinatra

Configure and use `Bullet::Rack`.

```ruby
configure :development do
  Bullet.enable = true
  Bullet.bullet_logger = true
  use Bullet::Rack
end
```

If your application generates a Content-Security-Policy via a separate middleware, ensure that `Bullet::Rack` is loaded _before_ that middleware.

### Run in tests

First you need to enable Bullet in the test environment.

```ruby
# config/environments/test.rb
config.after_initialize do
  Bullet.enable = true
  Bullet.bullet_logger = true
  Bullet.raise = true # raise an error if n+1 query occurs
end
```

**Note:** Controller and integration tests work automatically because Bullet's Rack middleware wraps each HTTP request with `Bullet.start_request` and `Bullet.end_request`. However, model tests and other tests that don't go through the Rack middleware (like direct model method calls) require manual wrapping with the test helper code below.

Then wrap each test in the Bullet api.

With RSpec:

```ruby
# spec/rails_helper.rb
RSpec.configure do |config|
  config.before(:each) do
    Bullet.start_request
  end

  config.after(:each) do
    Bullet.perform_out_of_channel_notifications if Bullet.notification?
    Bullet.end_request
  end
end
```

With Minitest:

```ruby
# test/test_helper.rb
module ActiveSupport
  class TestCase
    def before_setup
      Bullet.start_request
      super
    end

    def after_teardown
      super
      Bullet.perform_out_of_channel_notifications if Bullet.notification?
      Bullet.end_request
    end
  end
end
```

## Debug Mode

Bullet outputs some details info, to enable debug mode, set
`BULLET_DEBUG=true` env.

## Contributors

[https://github.com/flyerhzm/bullet/contributors](https://github.com/flyerhzm/bullet/contributors)

## Demo

Bullet is designed to function as you browse through your application in development. To see it in action,
you can follow these steps to create, detect, and fix example query problems.

1\. Create an example application

```
$ rails new test_bullet
$ cd test_bullet
$ rails g scaffold post name:string
$ rails g scaffold comment name:string post_id:integer
$ bundle exec rails db:migrate
```

2\. Change `app/models/post.rb` and `app/models/comment.rb`

```ruby
class Post < ApplicationRecord
  has_many :comments
end

class Comment < ApplicationRecord
  belongs_to :post
end
```

3\. Go to `rails c` and execute

```ruby
post1 = Post.create(:name => 'first')
post2 = Post.create(:name => 'second')
post1.comments.create(:name => 'first')
post1.comments.create(:name => 'second')
post2.comments.create(:name => 'third')
post2.comments.create(:name => 'fourth')
```

4\. Change the `app/views/posts/index.html.erb` to produce a N+1 query

```
<% @posts.each do |post| %>
  <tr>
    <td><%= post.name %></td>
    <td><%= post.comments.map(&:name) %></td>
    <td><%= link_to 'Show', post %></td>
    <td><%= link_to 'Edit', edit_post_path(post) %></td>
    <td><%= link_to 'Destroy', post, :confirm => 'Are you sure?', :method => :delete %></td>
  </tr>
<% end %>
```

5\. Add the `bullet` gem to the `Gemfile`

```ruby
gem "bullet"
```

And run

```
bundle install
```

6\. enable the Bullet gem with generate command

```
bundle exec rails g bullet:install
```

7\. Start the server

```
$ rails s
```

8\. Visit `http://localhost:3000/posts` in browser, and you will see a popup alert box that says

```
The request has unused preload associations as follows:
None
The request has N+1 queries as follows:
model: Post => associations: [comment]
```

which means there is a N+1 query from the Post object to its Comment association.

In the meantime, there's a log appended into `log/bullet.log` file

```
2010-03-07 14:12:18[INFO] N+1 Query in /posts
  Post => [:comments]
  Add to your finder: :include => [:comments]
2010-03-07 14:12:18[INFO] N+1 Query method call stack
  /home/flyerhzm/Downloads/test_bullet/app/views/posts/index.html.erb:14:in `_render_template__600522146_80203160_0'
  /home/flyerhzm/Downloads/test_bullet/app/views/posts/index.html.erb:11:in `each'
  /home/flyerhzm/Downloads/test_bullet/app/views/posts/index.html.erb:11:in `_render_template__600522146_80203160_0'
  /home/flyerhzm/Downloads/test_bullet/app/controllers/posts_controller.rb:7:in `index'
```

The generated SQL is:

```
Post Load (1.0ms)   SELECT * FROM "posts"
Comment Load (0.4ms)   SELECT * FROM "comments" WHERE ("comments".post_id = 1)
Comment Load (0.3ms)   SELECT * FROM "comments" WHERE ("comments".post_id = 2)
```

9\. To fix the N+1 query, change `app/controllers/posts_controller.rb` file

```ruby
def index
  @posts = Post.includes(:comments)

  respond_to do |format|
    format.html # index.html.erb
    format.xml  { render :xml => @posts }
  end
end
```

10\. Refresh `http://localhost:3000/posts`. Now there's no alert box and nothing new in the log.

The generated SQL is:

```
Post Load (0.5ms)   SELECT * FROM "posts"
Comment Load (0.5ms)   SELECT "comments".* FROM "comments" WHERE ("comments".post_id IN (1,2))
```

N+1 query fixed. Cool!

11\. Now simulate unused eager loading. Change
`app/controllers/posts_controller.rb` and
`app/views/posts/index.html.erb`

```ruby
def index
  @posts = Post.includes(:comments)

  respond_to do |format|
    format.html # index.html.erb
    format.xml  { render :xml => @posts }
  end
end
```

```
<% @posts.each do |post| %>
  <tr>
    <td><%= post.name %></td>
    <td><%= link_to 'Show', post %></td>
    <td><%= link_to 'Edit', edit_post_path(post) %></td>
    <td><%= link_to 'Destroy', post, :confirm => 'Are you sure?', :method => :delete %></td>
  </tr>
<% end %>
```

12\. Refresh `http://localhost:3000/posts`, and you will see a popup alert box that says

```
The request has unused preload associations as follows:
model: Post => associations: [comment]
The request has N+1 queries as follows:
None
```

Meanwhile, there's a line appended to `log/bullet.log`

```
2009-08-25 21:13:22[INFO] Unused preload associations: PATH_INFO: /posts;    model: Post => associations: [comments]·
Remove from your finder: :include => [:comments]
```

13\. Simulate counter_cache. Change `app/controllers/posts_controller.rb`
and `app/views/posts/index.html.erb`

```ruby
def index
  @posts = Post.all

  respond_to do |format|
    format.html # index.html.erb
    format.xml  { render :xml => @posts }
  end
end
```

```
<% @posts.each do |post| %>
  <tr>
    <td><%= post.name %></td>
    <td><%= post.comments.size %></td>
    <td><%= link_to 'Show', post %></td>
    <td><%= link_to 'Edit', edit_post_path(post) %></td>
    <td><%= link_to 'Destroy', post, :confirm => 'Are you sure?', :method => :delete %></td>
  </tr>
<% end %>
```

14\. Refresh `http://localhost:3000/posts`, then you will see a popup alert box that says

```
Need counter cache
  Post => [:comments]
```

Meanwhile, there's a line appended to `log/bullet.log`

```
2009-09-11 10:07:10[INFO] Need Counter Cache
  Post => [:comments]
```

Copyright (c) 2009 - 2022 Richard Huang (flyerhzm@gmail.com), released under the MIT license
