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updated changelog

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commit 0899be5798d20e3e886e5f741d3e4b1bf43afedd 1 parent fa3c4ea
Aaron Patterson authored July 29, 2012

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  1. 16  actionpack/CHANGELOG.md
16  actionpack/CHANGELOG.md
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 ## Rails 4.0.0 (unreleased) ##
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+*   Added ActionController::Live.  Mix it in to your controller and you can
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+    stream data to the client live.  For example:
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+
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+      class FooController < ActionController::Base
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+        include ActionController::Live
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+
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+        def index
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+          100.times {
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+            # Client will see this as it's written
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+            response.stream.write "hello world\n"
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+            sleep 1
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+          }
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+          response.stream.close
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+        end
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+      end
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+
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 *   Remove ActionDispatch::Head middleware in favor of Rack::Head. *Santiago Pastorino*
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 *   Deprecate `:confirm` in favor of `:data => { :confirm => "Text" }` option for `button_to`, `button_tag`, `image_submit_tag`, `link_to` and `submit_tag` helpers.

17 notes on commit 0899be5

adsummos

Streaming already exists since 3.1 by passing an object that responds to 'each' to respond_body. Does this duplicate the functionality or does it add something new? Are both methods now supported and if so, when would you use one over the other?

adsummos

I read that, however I'm not talking about streaming templates. See answer #2 at http://stackoverflow.com/questions/3507594/ruby-on-rails-3-streaming-data-through-rails-to-client
Is that not exactly the same thing with different syntax? Am I missing something?

Rafael Mendonça França
Owner

The main difference is that know you can control what is been stream to the user in runtime. In the way that already exists you have to construct the response before send to users

adsummos

We currently have an app that streams on 3.1 and 3.2 using the 'each' method and we construct the response as we are sending it because the response is too large to fit in memory and it would run into Heroku's 30 second time limit if we didn't start sending data soon enough. Could you give me an example of something you couldn't do with the existing method that you can do with the new one?

adsummos

I believe the 'each' streaming functionality comes from Rack, so maybe you didn't realize it was there? I can't really see anything that's fundamentally different between the two in terms of functionality. We stream a ~50 GB CSV file using the each method while reading from a DB cursor. Again, maybe I'm missing some new functionality this adds, but I'm not sure what it is.

Rafael Mendonça França
Owner

Again the main difference is that now you can control when and what is being sent to the client. Yes, we know that Rack have streaming functionality but these feature are not the same. Think about AC::Live as a socket.

adsummos
Rafael Mendonça França
Owner

Aha! Seem I was missing something. Sorry about that.

I did not participate from the discussion to add this feature and I was talking only with my knowledge about the topic.

I'll try to get more information about the topic, and try to answer with a more grounded knowledge if anyone answer first.

Thank you for the discussion and really sorry to make you loose your time explain me.

Aaron Patterson
Owner

@adsummos it's about control. Rather than waiting for Rack to pull data from your each method (IOW call your each method), this lets you push data to the response. As @rafaelfranca says, this API is for emulating a socket.

adsummos
Aaron Patterson
Owner

@adsummos The old method will work the same way, feel free to use it.

adsummos

I'm just trying to understand if this adds something new, and if so, what that is.

Aaron Patterson
Owner

@adsummos it adds an IO like API for writing to responses.

adsummos

so it is just the API? There is no fundamental difference between yield 'response' and response.stream.write 'response' in terms of functionality?

Ravil Bayramgalin

nice, finally streaming api I would use without nightmares :)

femto

Hello, @tenderlove, I use this code in puma
(thin seems not work, just hangs), it crashes
whenever the client closes stream(

rails-project/rails/actionpack/lib/action_dispatch/http/response.rb:75:in write': closed stream (IOError)
/rails-project/rails/actionpack/lib/action_controller/metal/live.rb:44:in
write'
...

So I debug a bit and found out the problem,

module ActionController
module Live
class Buffer < ActionDispatch::Response::Buffer #:nodoc:

  def write(string)
    unless @response.committed?
      @response.headers["Cache-Control"] = "no-cache"
      @response.headers.delete "Content-Length"
    end
    #raise IOError, "closed stream" if closed?
    begin
      @response.commit!
      @buf.push string
    rescue
    end
  end
end

end
end

the comment out line is what causes the problem, when commented out,
it's ok, so maybe adding this to fix?

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