Rapporteur (rap-or-TUHR)

This gem provides a singular, status-checking endpoint to your application. The endpoint provides a JSON response with either an HTTP 200 or an HTTP 500 response, depending on the current application environment.

When the environment tests successfully, an HTTP 200 response is returned with the current application Git revision and server time:

{
  "revision": "906731e6467ea381ba5bc70f103b85ed4178fee7",
  "time": "2013-05-19T05:38:46Z"
}

When an application validation fails, an HTTP 500 response is returned with a collection of error messages, similar to the Rails < 4.2 responders for model validations:

{
  "errors": {
    "database": ["The application database is inaccessible or unavailable"]
  }
}

Installation

To install, add this line to your application's Gemfile:

gem 'rapporteur'

And then execute:

$ bundle install

Supported environments

This library follows the maintenance policy of Ruby, Ruby on Rails, and Sinatra for testing and maintaining these environments.

Unsupported versions of Ruby, Ruby on Rails, or Sinatra may also work with this library, however they are not officially supported or tested against.

Usage

By default, there are no application checks that run and the status endpoint simply reports the current application revision and time. This is useful for a basic connectivity check to be watched by a third party service like Pingdom for a very simple, non-critical application.

You may optionally use any of the pre-defined checks (such as the ActiveRecord connection check) to expand the robustness of the status checks. Adding a check will execute that check each time the status endpoint is requested, so be somewhat wary of doing too much. See more in the Adding checks section, below.

Further, you can define your own checks which could be custom to your application or environment and report their own, unique errors. The only requirement is that the check objects are callable (respond to #call, like a Proc). See more in the Creating custom checks section, below.

Usage in a Rails application

If you're running in a Rails environment, then the included Rails Engine should automatically get required and loaded. However, you will need to instruct your application where to mount the status endpoint. In your config/routes.rb, add a mount at the endpoint you desire:

Rails.application.routes.draw do
  mount Rapporteur::Engine, at: '/status'
end

This will mount the Rapporteur status endpoint at /status where it will listen for and respond to JSON requests (/status.json, for example).

Usage in a Rack (non-Rails) application

If you're running in a non-Rails, Rack environment (e.g. Sinatra), you can require "rapporteur" and use the status generator directly from your own endpoints.

So, here is an example usage in Sinatra:

require "rapporteur"
require "sinatra/base"

class MyApp < Sinatra::Base
  get "/status.json" do
    content_type :json
    status(result.errors.empty? ? 200 : 500)
    body Rapporteur.run.as_json.to_json
  end
end

Require rapporteur and then, at some point, call Rapporteur.run to execute the configured checks. as_json will convert the result of the run into a Hash which is ready for JSON generation. At that point, do whatever you need to do with the Hash to have your framework of choice generate and respond with JSON.

Customization

Adding checks

This gem ships with the following checks tested and packaged:

• Rapporteur::Checks::ActiveRecordCheck - Performs a trivial test of the current ActiveRecord::Base.connection to ensure basic database connectivity.

To add checks to your application, define the checks you'd like to run in your environment or application configuration files or initializers, such as:

# config/initializers/rapporteur.rb
Rapporteur.add_check(Rapporteur::Checks::ActiveRecordCheck)

Or, make an environment specific check with:

# config/environments/production.rb
MyApplication.configure do
  config.to_prepare do
    Rapporteur.add_check(Rapporteur::Checks::ActiveRecordCheck)
  end
end

Creating custom checks

It is simple to add a custom check to the status endpoint. All that is required is that you give the checker an object that is callable. In your object, simply check for the state of the world that you're interested in, and if you're not happy with it, add an error to the given checker instance:

# config/initializers/rapporteur.rb

# Define a simple check as a block:
Rapporteur.add_check do |checker|
  checker.add_message(:paid, "too much")
end

# Make and use a reusable Proc or lambda:
my_proc_check = lambda { |checker|
  checker.add_error(:luck, :bad) if rand(2) > 0
  checker.add_message(:luck, :good)
}
Rapporteur.add_check(my_proc_check)

# Package a check into a Class:
class MyClassCheck
  def self.call(checker)
    @@counter ||= 0
    checker.add_error(:count, :exceeded) if @@counter > 50
  end
end
Rapporteur.add_check(MyClassCheck)

Certainly, the definition and registration of the checks do not need to occur within the same file, but you get the idea. Also: Please make your checks more useful than those defined above. ;)

You could create a checker for your active Redis connection, Memcached connections, disk usage percentage, process count, memory usage, or really anything you like. Again, because these checks get executed every time the status endpoint is called, be mindful of the tradeoffs when making a check that may be resource intensive.

Customizing the revision

If you need to customize the way in which the current application revision is calculated (by default it runs a git rev-parse HEAD), you may do so by modifying the necessary environment file or creating an initializer in your Rails application:

# config/initializers/rapporteur.rb
Rapporteur::Revision.current = "revision123"

# config/environments/production.rb
MyApplication.configure do
  config.to_prepare do
    Rapporteur::Revision.current = "revision123"
  end
end

You may pass a String or a callable object (Proc) to .current= and it will be executed and memoized. Useful examples of this are:

# Read a Capistrano REVISION file
Rapporteur::Revision.current = Rails.root.join("REVISION").read.strip

# Force a particular directory and use Git
Rapporteur::Revision.current = `cd "#{Rails.root}" && git rev-parse HEAD`.strip

# Use an ENV variable (Heroku Bamboo Stack)
Rapporteur::Revision.current = ENV["REVISION"]

# Do some crazy calculation
Rapporteur::Revision.current = lambda { MyRevisionCalculator.execute! }

Customizing the messages

The success and error messages displayed in the event that application validations pass or fail are all optionally passed through I18n. There are default localization strings provided with the gem, but you may override them as necessary, by simply redefining the proper locale keys in a locale file within your local application.

For example, to override the database check failure message:

# /config/locales/en.yml
en:
  rapporteur:
    errors:
      database:
        unavailable: "Something went wrong"

If you created a custom checker which reports the current sky color, for example, and wanted the success messages to be localized, you could do the following:

# /config/initializers/rapporteur.rb
sky_check = lambda { |checker| checker.add_message(:sky, :blue) }
Rapporteur.add_check(sky_check)

# /config/locales/fr.yml
fr:
  rapporteur:
    messages:
      sky:
        blue: "bleu"

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request