Class: Rack::Cascade

Relationships & Source Files
Inherits: Object
Defined in: lib/rack/cascade.rb


Cascade tries a request on several apps, and returns the first response that is not 404 or 405 (or in a list of configured status codes). If all applications tried return one of the configured status codes, return the last response.

Class Method Summary

Instance Attribute Summary

  • #apps readonly

    An array of applications to try in order.

Instance Method Summary

Constructor Details

.new(apps, cascade_for = [404, 405]) ⇒ Cascade

Set the apps to send requests to, and what statuses result in cascading. Arguments:

apps: An enumerable of rack applications. cascade_for: The statuses to use cascading for. If a response is received

from an app, the next app is tried.
[ GitHub ]

# File 'lib/rack/cascade.rb', line 21

def initialize(apps, cascade_for = [404, 405])
  @apps = []
  apps.each { |app| add app }

  @cascade_for = {}
  [*cascade_for].each { |status| @cascade_for[status] = true }

Instance Attribute Details

#apps (readonly)

An array of applications to try in order.

[ GitHub ]

# File 'lib/rack/cascade.rb', line 13

attr_reader :apps

Instance Method Details


Alias for #add.

[ GitHub ]

# File 'lib/rack/cascade.rb', line 65

alias_method :<<, :add

#add(app) Also known as: #<<

Append an app to the list of apps to cascade. This app will be tried last.

[ GitHub ]

# File 'lib/rack/cascade.rb', line 56

def add(app)
  @apps << app


Call each app in order. If the responses uses a status that requires cascading, try the next app. If all responses require cascading, return the response from the last app.

[ GitHub ]

# File 'lib/rack/cascade.rb', line 32

def call(env)
  return [404, { CONTENT_TYPE => "text/plain" }, []] if @apps.empty?
  result = nil
  last_body = nil

  @apps.each do |app|
    # The SPEC says that the body must be closed after it has been iterated
    # by the server, or if it is replaced by a middleware action. Cascade
    # replaces the body each time a cascade happens. It is assumed that nil
    # does not respond to close, otherwise the previous application body
    # will be closed. The final application body will not be closed, as it
    # will be passed to the server as a result.
    last_body.close if last_body.respond_to? :close

    result = app.call(env)
    return result unless @cascade_for.include?(result[0].to_i)
    last_body = result[2]


#include?(app) ⇒ Boolean

Whether the given app is one of the apps to cascade to.

[ GitHub ]

# File 'lib/rack/cascade.rb', line 61

def include?(app)