Ruby on Rails Web File Download Indicator

Objective: To show how to implement the file download indicator for various Ruby on Rails configurations:
I will divide the article series into three parts.
mongrel
mongrel (s) + nginx
mod_rails

The following is verified with:
Ruby on Rails 2.2.2
ruby 1.8.6 (2008-03-03 patchlevel 114) [universal-darwin9.0]
mongrel 1.1.5
Mac OS X 10.5.6


Part I. How to do this with mongrel

The article is based on a link to which is at the very end. But repeating it on my new rails and mnogrels nothing happened. I changed it a little.

Frame Building: Adding Routes:
rails upload
cd upload
rm public/index.html
script/generate controller home index upload progress
touch app/views/layouts/application.html.erb


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1. ActionController::Routing::Routes.draw do |map|
2.   map.root :controller => 'home'
3.   map.upload '/upload', :controller => 'home', :action => 'upload'
4.   map.progress '/progress', :controller => 'home', :action => 'progress'
5. end
6.  

The preparation phase is completed. Now we need to explain a little how the file upload indicator functions. The form submission should go to the iframe, and using the ajax request from the page itself, you can use the right frequency to contact a certain controller that will return the current state (you can use json, you can use html, here it is done by javascript), and depending on them, on the page move the indicator.

So, there is only one controller, and there are three methods in it: index to display the form for uploading, upload - processing the downloaded file, progress - to obtain data on the download status. The controller is as follows:

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1. class HomeController < ApplicationController
2.   skip_before_filter :verify_authenticity_token, :only => [:progress]
3.  
4.   def index
5.     @upid = Time.now.tv_sec.to_s
6.   end
7.  
8.   def upload
9.     render :text => 'done'
10.   end
11.  
12.   def progress
13.     @status = Mongrel::Uploads.check(params[:upload_id])
14.     respond_to do |format|
15.       format.js
16.     end
17.   end
18. end

skip_before_filter is needed since requests will go without a token. @upid is a unique identifier.
Now you need to write some kind of plugin for mongrel, which will intercept the file upload (more specifically, access to a specific url) and store data about the download status, in addition, you need to access this data somehow. It’s good that this has already been implemented and the code can be taken from svn:

svn co svn://rubyforge.org/var/svn/mongrel/trunk/projects/mongrel_upload_progress

I suggest doing this as follows: create the lib / progress_plugin.rb file with the following contents:

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1. class Upload < GemPlugin::Plugin "/handlers"
2.   include Mongrel::HttpHandlerPlugin
3.  
4.   def initialize(options = {})
5.     @path_info = Array(options[:path_info])
6.     @frequency = options[:frequency] || 3
7.     @request_notify = true
8.     if options[:drb]
9.       require 'drb'
10.       DRb.start_service
11.       Mongrel.const_set :Uploads, DRbObject.new(nil, options[:drb])
12.     else
13.       Mongrel.const_set :Uploads, Mongrel::UploadProgress.new
14.     end
15.     Mongrel::Uploads.debug = true if options[:debug]
16.   end
17.  
18.   def request_begins(params)
19.     upload_notify(:add, params, params[Mongrel::Const::CONTENT_LENGTH].to_i)
20.   end
21.  
22.   def request_progress(params, clen, total)
23.     upload_notify(:mark, params, clen)
24.   end
25.  
26.   def process(request, response)
27.     upload_notify(:finish, request.params)
28.   end
29.  
30.   private
31.     def upload_notify(action, params, *args)
32.       return unless @path_info.include?(params['PATH_INFO']) &&
33.         params[Mongrel::Const::REQUEST_METHOD] == 'POST' &&
34.         upload_id = Mongrel::HttpRequest.query_parse(params['QUERY_STRING'])['upload_id']
35.       if action == :mark
36.         last_checked_time = Mongrel::Uploads.last_checked(upload_id)
37.         return unless last_checked_time && Time.now - last_checked_time > @frequency
38.       end
39.       Mongrel::Uploads.send(action, upload_id, *args)
40.       Mongrel::Uploads.update_checked_time(upload_id) unless action == :finish
41.     end
42. end
43.  
44. # Keeps track of the status of all currently processing uploads
45. class Mongrel::UploadProgress
46.   attr_accessor :debug
47.   def initialize
48.     @guard = Mutex.new
49.     @counters = {}
50.   end
51.  
52.   def check(upid)
53.     @counters[upid].last rescue nil
54.   end
55.  
56.   def last_checked(upid)
57.     @counters[upid].first rescue nil
58.   end
59.  
60.   def update_checked_time(upid)
61.     @guard.synchronize { @counters[upid][0] = Time.now }
62.   end
63.  
64.   def add(upid, size)
65.     @guard.synchronize do
66.       @counters[upid] = [Time.now, {:size => size, :received => 0}]
67.       puts "#{upid}: Added" if @debug
68.     end
69.   end
70.  
71.   def mark(upid, len)
72.     return unless status = check(upid)
73.     puts "#{upid}: Marking" if @debug
74.     @guard.synchronize { status[:received] = status[:size] - len }
75.   end
76.  
77.   def finish(upid)
78.     @guard.synchronize do
79.       puts "#{upid}: Finished" if @debug
80.       @counters.delete(upid)
81.     end
82.   end
83.  
84.   def list
85.     @counters.keys.sort
86.   end
87. end
88.  

After that, create a config for mongrel (essentially a regular ruby-file) that will connect this plugin to mongrel: Put in mongrel_upload_progress.conf the following:
touch config/mongrel_upload_progress.conf


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1. require 'progress_plugin'
2. uri "/", :handler => plugin('/handlers/upload', :path_info => '/upload'), :in_front => true
3.  

path_info is a route that will be intercepted by the plugin to monitor the loading status.
The download form and all the necessary js-nicknames can be taken here .

It remains to simply run the mongrel with the configuration file: The indicator in the browser will look something like this: If you can use drb several mongrel, the details are described in the link below. I did not make any cosmetic changes in the framework of this article. In a more beautiful form, the indicator can be viewed on rghost.ru. Of course, it is a pity to admit that all this was written most likely in vain, since few people manage with a simple mingrel. Usually they put nginx in front of the mongrel or generally replace it with apache with mod_passenger. I plan to write articles about them later.
mongrel_rails start -S config/mongrel_upload_progress.conf


List of references

mongrel upload progress