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Make generated Metal bits a pure rack endpoint application (not middl…
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…eware)

Instead of calling super to pass the request on, return a 404.
The modified app looks like this:

  # app/metal/poller.rb
  class Poller
    def self.call(env)
      if env["PATH_INFO"] =~ /^\/poller/
        [200, {"Content-Type" => "text/html"}, "Hello, World!"]
      else
        [404, {"Content-Type" => "text/html"}, "Not Found"]
      end
    end
  end

But you aren't locked in to just Rails:

  # app/metal/api.rb
  require 'sinatra'
  Sinatra::Application.default_options.merge!(:run => false, :env => :production)
  Api = Sinatra.application unless defined? Api

  get '/interesting/new/ideas' do
    'Hello Sinatra!'
  end
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@josh
josh committed Dec 17, 2008
1 parent 97a178b commit 61a4115
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Showing 3 changed files with 13 additions and 19 deletions.
4 changes: 1 addition & 3 deletions railties/lib/initializer.rb
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Expand Up @@ -536,9 +536,7 @@ def initialize_i18n
end

def initialize_metal
Dir["#{configuration.root_path}/app/metal/*.rb"].each do |file|
configuration.middleware.use(File.basename(file, '.rb').camelize)
end
configuration.middleware.use Rails::Rack::Metal
end

# Initializes framework-specific settings for each of the loaded frameworks
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20 changes: 8 additions & 12 deletions railties/lib/rails/rack/metal.rb
View file
@@ -1,21 +1,17 @@
module Rails
module Rack
class Metal
def self.new(app)
apps = Dir["#{Rails.root}/app/metal/*.rb"].map do |file|
File.basename(file, '.rb').camelize.constantize
end
apps << app
::Rack::Cascade.new(apps)
end

NotFound = lambda { |env|
[404, {"Content-Type" => "text/html"}, "Not Found"]
}

def self.call(env)
new(NotFound).call(env)
end

def initialize(app)
@app = app
end

def call(env)
@app.call(env)
end
end
end
end
8 changes: 4 additions & 4 deletions railties/lib/rails_generator/generators/components/metal/templates/metal.rb
View file
@@ -1,12 +1,12 @@
# Allow the metal piece to run in isolation
require(File.dirname(__FILE__) + "/../../config/environment") unless defined?(Rails)

class <%= class_name %> < Rails::Rack::Metal
def call(env)
class <%= class_name %>
def self.call(env)
if env["PATH_INFO"] =~ /^\/<%= file_name %>/
[200, {"Content-Type" => "text/html"}, "Hello, World!"]
[200, {"Content-Type" => "text/html"}, ["Hello, World!"]]
else
super
[404, {"Content-Type" => "text/html"}, ["Not Found"]]
end
end
end

23 comments on commit 61a4115

@trevorturk
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Just curious why the generator has been changed to return an array instead of a string now…?

BTW – that you can use Sinatra this easily is 100% awesome. Thank you.

@josh
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@josh josh commented on 61a4115 Dec 17, 2008

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@trevorturk Returning strings is being removed from the Rack spec since Ruby 1.9 doesn’t have String#each. Long story: http://groups.google.com/group/rack-devel/browse_thread/thread/e6132c3509438df

@bryanl
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@bryanl bryanl commented on 61a4115 Dec 17, 2008

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I like this much better. Great work Josh!

@jnewland
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@josh Awesome, it’s easier to understand the distinction between Metal and Middleware now. Updated my blog post to match.

@tjogin
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@tjogin tjogin commented on 61a4115 Dec 17, 2008

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The distinction between metal and middleware became clearer, but IMHO the useage turned towards the ugly side.

Here’s how I’d like it to look:

# app/metal/poller.rb
  class Poller
    def self.call(env)
      if env["PATH_INFO"] =~ /^\/poller/
        [200, {"Content-Type" => "text/html"}, "Hello, World!"]
      end
    end
  end

@josh
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@josh josh commented on 61a4115 Dec 17, 2008

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@tjogin The initial Rails::Metal class hid this stuff from you. However the initial confusion made me decide to expose it. Nothing magic anymore, thats just a class.

@heycarsten
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This is awesome.

@tjogin
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@tjogin tjogin commented on 61a4115 Dec 17, 2008

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@josh: Personally, I liked it hidden. :P

@matthewrudy
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yeah.
I also liked the way it was.

I think that the default 404 is going to cause the most confusion,
It makes me think “I dont want to return a 404!”,
and I’d probably delete it.

Saying that, a magical “super” is probably equally as brittle.

Anyway,
its good stuff.

@foca
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@foca foca commented on 61a4115 Dec 18, 2008

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What about defining a constant Metal::PassThru = [404, {"Content-Type" => "text/html"}, ["Not Found"]]

And then in the code you can just return Metal::PassThru and voila, you keep the logic plain and simple, and the “magic” 404 becomes a name which clearly states your intentions.

@foca
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@foca foca commented on 61a4115 Dec 18, 2008

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or maybe it’s clearer if PassThru is an exception and the code that adds each metal class on the call chain rescues PassThru and does a next on the iterator? (I didn’t look at the implementation, so maybe this won’t work)

But you get the idea.

@splattael
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@foca
NotFound? http://github.com/rails/rails/tree/61a41154f7d50099da371e0d2f22fd25ab9113c2/railties/lib/rails/rack/metal.rb#L12

@bumi
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@bumi bumi commented on 61a4115 Dec 18, 2008

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@foca +1

@pkoch
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@pkoch pkoch commented on 61a4115 Dec 21, 2008

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what if I really want to 404?

@skade
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@skade skade commented on 61a4115 Jan 18, 2009

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One question: the Rack specification says that Rack-Applications are not allowed to be Classes. AFAIK, it doesn’t enforce this, but wouldn’t it be good to stick to the Spec?

I’m okay with using Cascade and 404.

@josh
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@josh josh commented on 61a4115 Jan 19, 2009

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@skade A valid rack application is anything that responds to “call”, there are no type requirements. Even if you wanted to restrict this to objects, in Ruby classes are objects ;)

@pager
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@pager pager commented on 61a4115 Jan 19, 2009

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@josh http://rack.rubyforge.org/doc/files/SPEC.html
“A Rack application is an Ruby object (not a class) that responds to call”

@skade
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@skade skade commented on 61a4115 Jan 19, 2009

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@josh: yes, ruby classes are objects. Thanks for the lesson… But they are special objects with subtle differences. There is a distinction, although classes behave like objects in almost every case. For example: classes are (usually) globally unique, objects (usually) not.
And that might just be the reason why the spec explicitly forbids classes.

@kairichard
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woot, this is gonna be huge +1

@cypher
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@cypher cypher commented on 61a4115 Jan 20, 2009

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@skade, pager: “object, not a class” means that Rack won’t try to instantiate anything for you. As Josh correctly points out, all it wants is an object that has a “call” method, and classes are objects too.

@skade
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@skade skade commented on 61a4115 Jan 20, 2009

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@cypher, josh: this may be up to interpretation, but I don’t really want to push this.

On the other hand: if you skip Metals implementing #call on a class level and just instantiate them, you even save the need for self. The default construction for Objects is an empty one, so this is easy. I find it a much better interface, especially because of the symmetry to controller actions.

@foca
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@foca foca commented on 61a4115 Jan 23, 2009

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@skade you can always just say

class MyMetal
  def self.call(env)
    new.call(env)
  end

  def call(env)
    # do your stuff here
  end
end

@jduff
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@jduff jduff commented on 61a4115 Jun 18, 2009

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Does anyone know of an actual workaround or patch so that I can return a 404 from my metal? The docs(http://guides.rubyonrails.org/rails_on_rack.html) say to use some other Rack middleware but I'm not really sure how I'm supposed to differentiate between the 404 my metal returns to say pass on to rails and the 404 I actually want to return to the user.

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