Live stream a database dump (or any other STDOUT) using Rails 4. Why would you want this? If you have a large database dump and want to avoid storing it in memory as Rails streams it. This allows pipe the dump directly into the http response instead of storing it as a file, sending it, and then deleting it. Let me know what you think! I've teste…

live_database_dump.rb

class DatabaseController < ApplicationController
  def database_dump
    database = Rails.configuration.database_configuration[Rails.env]["database"]
    send_file_headers!(:type => 'application/octet-stream', :filename => "#{database}_#{Time.now.to_s(:human)}.backup")

    pipe = IO.popen("pg_dump '#{database}' -F c")
    stream = response.stream
    while (line = pipe.gets)
      stream.write line
      sleep 0.0001 # HACK: Prevent server instance from sleeping forever if client disconnects during download
    end
  rescue IOError
    # Client Disconnected
  ensure
    pipe.close
    response.stream.close
  end
  
  # Code that allows us to only mix in the live methods if we're accessing the desired action

  def dispatch(name, *args)
    extend ActionController::Live if name.to_s == 'database_dump'
    super
  end
end

@njakobsen btw, you probably don't want to use gets here: I imagine read(n) will be much more efficient. Most of the "lines" you see are going to be pretty tiny.