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Merge pull request #1 from rwdaigle/article

Tweak message publishing process to be continuous. Update README.
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2 parents 2909ce7 + 03971ff commit 7f67175454395444d81982c2db0c961ce62d2107 @benzenwen benzenwen committed Mar 24, 2012
Showing with 26 additions and 125 deletions.
  1. +1 −0 .rvmrc
  2. +14 −110
  3. +11 −15 writer.rb
1 .rvmrc
@@ -0,0 +1 @@
+rvm use ruby-1.9.2@demo.tractorpush-writer --create
@@ -1,117 +1,21 @@
-# Tractor Push: A Real-time Demo with Ruby, Node.js, and MongoDB on Heroku Cedar
+This application is the message-publishing portion of the system described in [this Heroku Dev Center article](
+The Node.js web-component can be found at:
-Learn how to use three rising infrastructure technologies that put
-real-time interactivity into Web apps: ``, `Node.js` and
-`MongoDB`. Real-time interactivity examples include chat, large-scale
-games, editing collaboration, and low-latency notification. In a
-market with dynamic, mobile, and social applications, a strong Web
-interface is still an important component to the entire experience.
-To demonstrate cross-app functionality with an existing Ruby
-application, the article first walks through using a separate Heroku
-app to write to a shared MongoDB acting as a simple queue.
-Fortuitously, Heroku’s new Celadon Cedar stack offers several features
-that support these techniques: a polyglot stack and flexible worker
-dynos that connect to arbitrary queuing systems.
+#### Deploy
-<p class="callout" markdown="1"> Part I code:
-<a href=""></a></p>
-<p class="callout" markdown="1"> Part II code:
-<a href=""></a></p>
+Create the app on Heroku and add the MongoLab add-on.
-## Overview
+$ heroku create -s cedar tp-writer
+$ heroku addons:add mongolab
-<img src="" width="822" height="401" alt="Overview of TractorPush components."/>
-In the rest of the article, you
+Next, [configure the required MongoDB capped collection](
-* create the database,
-* connect a writer in Ruby,
-* connect a reader in Node.js,
-* instruct a browser to connect over
+Then deploy to Heroku and scale the `worker` process.
-First, create a MongoDB collection on MongoLab that serves as a simple
-but flexible message queue. The Ruby application writes documents to
-the collection, and a Node.js application reads the documents on
-demand. The read query in Node.js is initiated by a browser request.
-The query returns a tailable cursor to read documents as they arrive.
-Additionally, the browser negotiates a XHR-long polling process to
-simulate a push of documents to the browser. In effect, the entire
-stack, from database to browser presentation works in a push
-notification manner.
-<p class="callout" markdown="1">As of this writing, Heroku does not
-support the newer true push WebSocket protocol. XHR-long polling works acceptably. </p>
-<img src="" width="841" height="563" alt="End user screenshot of TractorPush demo."/>
-From an end user perspective, a browser window updates as existing
-messages are sent. Once the existing messages are exhausted, the
-browser window is static until new messages arrive at the server. As
-they arrive, the browser window continues to update. For the
-impatient: shows the running
-Given MongoDB's schema-free design, our messages can be arbitrarily
-complex JSON. In this demonstration to show the flexibility of the
-object marshalling and unmarshalling, there are three types of
-document-based messages that are pushed through the system:
-* simple (name-value),
-* array,
-* complex (nested documents).
-To demonstrate filtering of the different types of messages on the
-queue, one area of the screen shows all types of messages: with their
-sequence number and time of creation. In a second side of the screen,
-only complex-type messages are shown.
-# Running instance
-A running version of the demo is at:
-The server is node.js running It reads from a capped
-MongoDB database with a tailable cursor. A secondary set of servers
-(it happens to be in Ruby) writes to the database.
-Note: Sequence numbers may not be unique.
-In the online demo, the node.js and Ruby components are running on
-Heroku's Celedon Cedar stack. The MongoDB database is hosted at
-MongoLab. See and for more information.
-See: (TODO: URL) for detailed instructions on how to run the demo, but succintly:
-* Create a mongodb database 'testdatabase' with a capped collection 'messages' on localhost OR use Heroku and create a MONGOLAB database.
-* Run tractorpush-writer-ruby to insert files
-* Run 'npm install' Run tractorpush-server (this project): 'node app.js'
-* Point your browser to http://localhost:2000 and enjoy
-# Server REQUIRES
-* Node.js 0.6.9 +
-* npm 1.1.0-3
-* see package.json for more dependencies ( and mongodb)
-Original Demo: 2012 March by ObjectLabs Corporation, makers of hosted MongoDB.
-If you have comment or questions please contact us at @mongolab on Twitter or support AT Thanks for looking.
-## Legal stuff
-Copyright 2012 ObjectLabs Corporation.
-Code licensed under the Apache License, Version 2.0 (the "Apache
-License"); you may not use this file except in compliance with
-the Apache License. You may obtain a copy of the License at
-Unless required by applicable law or agreed to in writing, software
-distributed under the Apache License is distributed on an "AS IS"
-implied. See the Apache License for the specific language governing
-permissions and limitations under the Apache License.
-Non-code content licensed under Creative Commons
-Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0) at
+$ git push heroku master
+$ heroku ps:scale worker=1
@@ -37,11 +37,11 @@
require 'mongo'
require 'pp'
-uristring = ENV['MONGOLAB_URI'] || 'mongodb://localhost/testdatabase'
-debug = ENV['WRITER_DEBUG'] || "false"
-rate = ENV['WRITER_RATE'].to_f
-if (rate = 0.0) then rate = 10.0 end
+STDOUT.sync = true # Write in real-time
+uristring = ENV['MONGOLAB_URI'] || 'mongodb://localhost/testdatabase'
+debug = ENV['WRITER_DEBUG'] ? ENV['WRITER_DEBUG'] == "true" : false
+rate = ENV['WRITER_RATE'] ? ENV['WRITER_RATE'].to_i : 1 # Every second, write a message
uri = URI.parse(uristring)
conn = Mongo::Connection.from_uri(uristring)
@@ -53,17 +53,13 @@
{'messagetype' => 'array', 'ordinal' => 0, 'somearray' => ['a', 'b', 'c', 'd']},
{'messagetype' => 'complex', 'ordinal' =>0, 'subdocument' => {'fname' => 'George', 'lname' => 'Washington', 'subproperty' => 'US-president'}}]
-count = 500
-print("starting insertion of ", count, " documents into ", uri.scheme, "://",, uri.path, "\n")
-for i in 1..count
+# Run until killed
+i = 0
doc = docs[rand(3)].dup # MongoDB collection.insert mutates document, editing the _id key; we need a deep dup (copy).
doc['time'] = * 1000 # Switch to Javascript's convention
- doc['ordinal'] = i
+ doc['ordinal'] = i + 1
coll.insert(doc, :safe => true)
- if (debug == "true") then pp (doc) end
- sleep(1.0/rate)
-print("Finished. Inserted ", count, " messages.\n")
+ debug ? pp(doc) : puts("Inserting #{doc['messagetype']} message")
+ sleep(rate)

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