# 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** >= 3.0 and **mongoid** >= 2.4.1.
If you use activerecord 2.x, please use bullet <= 4.5.0
## External Introduction
* [http://railscasts.com/episodes/372-bullet](http://railscasts.com/episodes/372-bullet)
* [http://ruby5.envylabs.com/episodes/9-episode-8-september-8-2009](http://ruby5.envylabs.com/episodes/9-episode-8-september-8-2009)
* [http://railslab.newrelic.com/2009/10/23/episode-19-on-the-edge-part-1](http://railslab.newrelic.com/2009/10/23/episode-19-on-the-edge-part-1)
* [http://weblog.rubyonrails.org/2009/10/22/community-highlights](http://weblog.rubyonrails.org/2009/10/22/community-highlights)
## Install
You can install it as a gem:
```
gem install bullet
```
or add it into a Gemfile (Bundler):
```ruby
gem "bullet", :group => "development"
```
## Configuration
Bullet won't do ANYTHING 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.alert = true
Bullet.bullet_logger = true
Bullet.console = true
Bullet.growl = 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.bugsnag = true
Bullet.airbrake = true
Bullet.rollbar = true
Bullet.add_footer = true
Bullet.stacktrace_includes = [ 'your_gem', 'your_middleware' ]
Bullet.slack = { webhook_url: 'http://some.slack.url', foo: 'bar' }
end
```
The notifier of Bullet is a wrap of [uniform_notifier](https://github.com/flyerhzm/uniform_notifier)
The code above will enable all seven of the Bullet notification systems:
* `Bullet.enable`: enable Bullet gem, otherwise do nothing
* `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.rails_logger`: add warnings directly to the Rails log
* `Bullet.bugsnag`: add notifications to bugsnag
* `Bullet.airbrake`: add notifications to airbrake
* `Bullet.rollbar`: add notifications to rollbar
* `Bullet.console`: log warnings to your browser's console.log (Safari/Webkit browsers or Firefox w/Firebug installed)
* `Bullet.growl`: pop up Growl warnings if your system has Growl installed. Requires a little bit of configuration
* `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.raise`: raise errors, useful for making your specs fail unless they have optimized queries
* `Bullet.add_footer`: adds the details in the bottom left corner of the page
* `Bullet.stacktrace_includes`: include paths with any of these substrings in the stack trace, even if they are not in your main app
* `Bullet.slack`: add notifications to slack
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
```
## Whitelist
Sometimes Bullet may notify you of query problems you don't care to fix, or
which come from outside your code. You can whitelist these to ignore them:
```ruby
Bullet.add_whitelist :type => :n_plus_one_query, :class_name => "Post", :association => :comments
Bullet.add_whitelist :type => :unused_eager_loading, :class_name => "Post", :association => :comments
Bullet.add_whitelist :type => :counter_cache, :class_name => "Country", :association => :cities
```
## Log
The Bullet log `log/bullet.log` will look something like this:
* N+1 Query:
```
2009-08-25 20:40:17[INFO] N+1 Query: PATH_INFO: /posts; model: Post => associations: [comments]·
Add to your finder: :include => [:comments]
2009-08-25 20:40:17[INFO] N+1 Query: method call stack:·
/Users/richard/Downloads/test/app/views/posts/index.html.erb:11:in `_run_erb_app47views47posts47index46html46erb'
/Users/richard/Downloads/test/app/views/posts/index.html.erb:8:in `each'
/Users/richard/Downloads/test/app/views/posts/index.html.erb:8:in `_run_erb_app47views47posts47index46html46erb'
/Users/richard/Downloads/test/app/controllers/posts_controller.rb:7:in `index'
```
The first two lines are notifications that N+1 queries have been encountered. The remaining lines are stack traces 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] Unused eager loadings: PATH_INFO: /posts; model: Post => associations: [comments]·
Remove from your finder: :include => [:comments]
```
These two 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]
```
## Growl, XMPP/Jabber and Airbrake Support
see [https://github.com/flyerhzm/uniform_notifier](https://github.com/flyerhzm/uniform_notifier)
## Important
If you find Bullet does not work for you, *please disable your browser's cache*.
## Advanced
### Profile a job
The Bullet gem uses rack middleware to profile requests. If you want to use Bullet without an http server, like to profile a job, you can use use profile method and fetch warnings
```ruby
Bullet.profile do
# do anything
warnings = Bullet.warnings
end
```
### Work with sinatra
Configure and use `Bullet::Rack`
```ruby
configure :development do
Bullet.enable = true
Bullet.bullet_logger = true
use Bullet::Rack
end
```
### Run in tests
First you need to enable Bullet in 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
```
Then wrap each test in Bullet api.
```ruby
# spec/spec_helper.rb
if Bullet.enable?
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
```
## 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, 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 rake db:migrate
```
2\. Change `app/model/post.rb` and `app/model/comment.rb`
```ruby
class Post < ActiveRecord::Base
has_many :comments
end
class Comment < ActiveRecord::Base
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| %>
| <%= post.name %> |
<%= post.comments.map(&:name) %> |
<%= link_to 'Show', post %> |
<%= link_to 'Edit', edit_post_path(post) %> |
<%= link_to 'Destroy', post, :confirm => 'Are you sure?', :method => :delete %> |
<% end %>
```
5\. Add the `bullet` gem to the `Gemfile`
```ruby
gem "bullet"
```
And run
```
bundle install
```
6\. enable the Bullet gem in development, add a line to
`config/environments/development.rb`
```ruby
config.after_initialize do
Bullet.enable = true
Bullet.alert = true
Bullet.bullet_logger = true
Bullet.console = true
# Bullet.growl = true
Bullet.rails_logger = true
Bullet.add_footer = true
end
```
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 meanwhile, 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| %>
| <%= post.name %> |
<%= link_to 'Show', post %> |
<%= link_to 'Edit', edit_post_path(post) %> |
<%= link_to 'Destroy', post, :confirm => 'Are you sure?', :method => :delete %> |
<% 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| %>
| <%= post.name %> |
<%= post.comments.size %> |
<%= link_to 'Show', post %> |
<%= link_to 'Edit', edit_post_path(post) %> |
<%= link_to 'Destroy', post, :confirm => 'Are you sure?', :method => :delete %> |
<% 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 - 2015 Richard Huang (flyerhzm@gmail.com), released under the MIT license