Pingable

Pingable is a simple framework to implement a 'ping' URL in Rack-based web applications.

For example, a Rails or Sinatra app's config.ru may look like this (Rack 1.4.0 and later):

map '/ping' do
  run Pingable::Handler
end
run MyApp

Now you can add checks in a modular fashion:

Pingable.add_check lambda {
  unless check_something
    "Oh noes, something failed"
  end
}

Checks

A check is simply an object which:

• implements call with no arguments.
• returns one of the following on error:
  • a string
  • a hash of {:message => message}
  • an array of the above
• returns nil on success.

Something a bit more complex:

class TwitterCheck
  def initialize(url)
    @url = url
  end

  def call
    # ... check the URL ...
  end
end

Pingable.add_check TwitterCheck.new(:url => "http://twitter.com/")

Configuration

To set the name that a successful ping check will return, provide a name in the rackup file:

map '/ping' do
  use Pingable::Handler.new('my fancy app')
end
run MyApp

Ping check

/ping is implemented by running all registered checks.

On failure, an HTTP 503 is returned, with the body of the response being a text/plain text with each error on separate lines.

On success, a 200 OK is returned, with either the application's name as the body (if defined), or an empty body.

Common checks

Pingable comes with a set of checks that are commonly needed for web applications:

• Pingable.active_record_checks!: Checks ActiveRecord.
• Pingable.rails_cache_checks!: Checks Rails cache.

To install all common checks based on available dependencies:

Pingable.common_checks!

For example, if ActiveRecord has not been required, then the ActiveRecord check is not included.

License

Licensed under the MIT license. See LICENSE file.