Rails 3.2 Streaming

Rails 3.2 streaming

The edited question turned out to contain exactly the answer I needed. Posting it here as an answer.

The answer to getting the Rack handler to stream properly is apparently to add a Last-Modified header to the response:

self.response.headers['Last-Modified'] = Time.now.ctime.to_s

Streaming CSV Download from Rails 3.2 app

OK, after a bit more research I hacked together the following in my controller. It'll stream if response_body is given something enumeratable (is that a word?). Also, the server needs to be able to stream (I am using Unicorn on Heroku). I'd like very much to not have all this stuff in the controller, so my next step is to extract it out somehow.

  format.csv {
    @entries = Entry.all
    @columns = ["First Name", "Last Name"].to_csv
    @filename = "entries-#{Date.today.to_s(:db)}"

    self.response.headers["Content-Type"] ||= 'text/csv'
    self.response.headers["Content-Disposition"] = "attachment; filename=#{@filename}"
    self.response.headers["Content-Transfer-Encoding"] = "binary"

    self.response_body = Enumerator.new do |y|
      @entries.each_with_index do |entry, i|
        if i == 0
          y << @columns
        end
        y << [entry.first_name, entry.last_name].to_csv
      end
    end
  }

Ruby on Rails 3: Streaming data through Rails to client

It looks like this isn't available in Rails 3

https://rails.lighthouseapp.com/projects/8994/tickets/2546-render-text-proc

This appeared to work for me in my controller:

self.response_body =  proc{ |response, output|
  output.write "Hello world"
}

unexpected filter behavior in rails streaming controlle

It seems like, rather than relying on around_filter, you might be able to invoke your data clean-up routine in the class's each method after the iterator has been exhausted:

class Asdf
  def each
    (1..5).each do |num|
      sleep(1)
      Rails.logger.info "STREAMING LINE #{num}"
      yield "test#{num}\n"
    end
    Rails.logger.info "ALL DONE; READY TO CLEAN UP"
    clean_up
  end

  def clean_up
    Rails.logger.info "CLEANING UP"
  end
end

Hititng the welcome#index action in a Rails 3.2 app yielded the following in the log:

Started GET "/welcome" for 127.0.0.1 at 2016-01-25 18:55:49 -0800
Processing by WelcomeController#index as HTML
before_filter called
around_filter prior to action
around_filter after action
after_filter called
Completed 200 OK in 0.5ms (ActiveRecord: 0.0ms)
STREAMING LINE 1
STREAMING LINE 2
STREAMING LINE 3
STREAMING LINE 4
STREAMING LINE 5
ALL DONE; READY TO CLEAN UP
CLEANING UP

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