Building a Video Sharing App with Server Messaging in Ruby

In this tutorial, you will learn how to create a basic video sharing application prototype using rails.

The features includes:

• Signing up, in and out - we will use devise for that
• Uploading video - Simple upload, we will need to handle encoding for web formats
• Playing video - we will use basic videojs snippet to create simple video player
• Notifications - we would like to notify user when encoding is done and create scaffold for notifications system, we will use pubnub for that
• Like counter - simple example how to update page elements dynamically with usage of pubnub lib

Requirements

• Some knowledge about Ruby on Rails, CoffeeScript and HAML. Installed ffmpeg and redis on development machine

Setting up Basic Elements

Let's create new rails application:

rails new VideoShrimp

We won't be focusing on tests here so you can add -T flag to skip tests. SQLite will be used in this example but feel free to use postgresql, mysql or anything that you would like.

Please make sure you have installed rails 4.1 or newer. When I'm creating this tutorial I'm using:

> rails -v
Rails 4.2.4
> ruby -v
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin15]

When we have our rails app generated, let's add gems that we will use to Gemfile.

gem 'haml'
gem 'devise'
gem 'simple_form'
gem 'paperclip'
gem 'bootstrap-sass'
gem 'sidekiq'
gem 'sidetiq', github: 'sfroehler/sidetiq', branch: 'celluloid-0-17-compatibility'
gem 'pubnub',  github: 'pubnub/ruby', branch: 'celluloid'
gem 'sinatra', :require => nil
group :development do
  gem 'pry'
  gem 'pry-rails'
end

And some explanation:

• haml - We'll use haml for templates. Much better than classical *.html.erb I can reccomend slim too. If you want to stick with html.erb you will have to write some more code but it's fine.
• devise - We do want to have authorization on VideoShrimp and we don't want to spend too much time on it so we will use ready library. We will use just small part of devise power but it will speed up a little our development.
• simple_form - Another "make life easier" gem. It generates nice forms with less typing.
• paperclip - It gem that makes managing attachments easier. To be honest we don't need it in our app but I would like to show some basic functionality of that gem.
• bootstrap-sass - No need to comment, I guess.
• sidekiq - For video processing in background. It runs as separate process and is nicely scalable.
• sidetiq - For reoccurring jobs in Sidekiq - you can think about it as sidekiq plugin. We will need it to check if there's any unpublished video that is already encoded and publish it.
• pubnub - For notifications and some backend-frontend communication. Really easy to use and full of features system.
• sinatra - For sidekiq frontend, it's optional dependency.
• pry - Better irb
• pry-rails - Loads pry insted of irb via rails c

Important note #1: As you can see, sidekiq gem is fetched from other repository than official, it's because official gem isn't compatibilie with newest celluloid (at least when I'm writing this).

Important note #2: pubnub gem is fetched from different branch than master because celluloid version it's not yet official stable. Therefore we will use beta version from celluloid branch insted of current master version (celluloid version is refactored and uses celluloid insted of eventmachine).

Let's run standard bundle install to download added gems.

bundle install

Installing Devise and simple_form

SimpleForm has to be initialized by command:

rails generate simple_form:install --bootstrap

We're adding --bootstrap flag because, well, we'll use bootstrap. That will generate two initializers, locale file and template file.

Devise has to be inititalized by similar command:

rails generate devise:install

That will generate config/initializers/devise.rb and config/locales/devise.en.yml you don't need to care about these files right now as we don't need any additional devise configuration for this example.

Let's generate devise views where simple form will be used:

rails generate devise:views

When we have our project set up it's time for models and migrations.

Generating User Model

We're using devise so let's generate a user with that:

> rails generate devise user
      invoke  active_record
      create    db/migrate/20151117181300_devise_create_users.rb
      create    app/models/user.rb
      invoke    test_unit
      create      test/models/user_test.rb
      create      test/fixtures/users.yml
      insert    app/models/user.rb
       route  devise_for :users

Well, for this tutorial we don't need anything else here yet. By default user will have unique email and will be signing in using it.

Generating Video Model

We're generating Video model with command:

rails generate model Video name:string video_file:attachment mp4_file:attachment webm_file:attachment ogg_file:attachment thumbnail:attachment published:boolean likes:integer user:references

That migration needs one additional thing - likes default value of 0. Your migration should look like that:

class CreateVideos < ActiveRecord::Migration
  def change
    create_table :videos do |t|
      t.string :name
      t.attachment :video_file
      t.attachment :mp4_file
      t.attachment :webm_file
      t.attachment :ogg_file
      t.attachment :thumbnail
      t.boolean :published
      t.integer :likes, default: 0
      t.references :user, index: true, foreign_key: true
      t.timestamps null: false
    end
  end
end

Now model code.

class Video < ActiveRecord::Base
  # Association declaration
  belongs_to :user
  # Paperclip attachments declaration
  has_attached_file :video_file
  has_attached_file :mp4_file
  has_attached_file :webm_file
  has_attached_file :ogg_file
  # Styles declaration makes paperclip to use imagemagick to resize image to given size
  has_attached_file :thumbnail, styles: { medium_nr: "250x150!" }
  # Paperclip requires to set attachment validators
  validates_attachment_content_type :video_file, content_type: /\Avideo/
  validates_attachment_content_type :mp4_file, content_type: /.*/
  validates_attachment_content_type :webm_file, content_type: /.*/
  validates_attachment_content_type :ogg_file, content_type: /.*/
  # We want video model always to have :video_file attachment
  validates_attachment_presence :video_file
  # Publish video makes it available
  def publish!
    self.published = true
    save
  end
  # Increment likes counter
  def like!
    self.likes += 1
    save
  end
  # Decrease likes counter
  def dislike!
    self.likes -= 1
    save
  end
  # Checks if all formats are already encoded, the simplest way
  def all_formats_encoded?
    self.webm_file.path && self.mp4_file.path && self.ogg_file.path ? true : false
  end
end

The code is self-explanatory so I won't bother you with more comments here.
User model needs to be updated because of relation with Video:

class User < ActiveRecord::Base
  # Association declaration 
  has_many :videos
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable
end

Running Migrations

Great, so we have our models coded and migrations ready to migrate, let's do this.

rake db:migrate

Controllers and Views

Now, let's create controllers and views for VideoShrimp. We should allow users to create account and sign in.

We will add separate clean layout for devise. Starting form app/controllers/application_controller.rb let's define layout:

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception
  layout :layout_by_resource
  protected
  def layout_by_resource
    if devise_controller?
      'devise'
    else
      'application'
    end
  end
end

We're checking here of current controller is devise controller and return devise if true. If it's other controller (video, user, anything else) we will return standard application layout.

Now the app/views/layouts/devise.haml

!!!
%html
  %head
    %title VideoShrimp
    = stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track' => true
    = javascript_include_tag 'application', 'data-turbolinks-track' => true
    = csrf_meta_tags
  %body{'data-no-turbolink': true}
    .container
      .row
        .col-md-4.col-md-offset-4
          %h1.text-center VideoShrimp
          = yield

In devise layout we need just to include basic stuff. container, row, .col-md-4 and .col-md-offset-4 are bootstrap grid classes. If you don't know them I encourage you to read about Bootstrap Grid System.

Great. Now let's create users_controller.rb under app/controllers

class UsersController < ApplicationController
  # Checks if user is signed in before running controller, functionality provided by devise
  before_action :authenticate_user!
  before_action :set_user, only: [:show]
  before_action :set_current_user, only: [:edit, :update]
  def index
    @users = User.all
  end
  def show
  end
  def update
    respond_to do |format|
      if @user.update(user_params)
        format.html { redirect_to @user, notice: 'User was successfully updated.' }
        format.json { render :show, status: :ok, location: @user }
      else
        format.html { render :edit }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end
  private
  def set_user
    @user = User.find(params[:id])
  end
  def set_current_user
    @user = current_user
  end
  def user_params
    params.require(:user).permit(:email)
  end
end

That's quite really basic user controller that will allow us to display user profile and user to change his email.

We need videos controller too!

class VideosController < ApplicationController
  before_action :authenticate_user!
  before_action :set_video, only: [:show, :edit, :like, :dislike]
  # All published videos
  def index
    @videos = Video.where(published: true)
  end
  def show
  end
  def new
    @video = Video.new
  end
  def edit
  end
  def create
    @video = Video.new(video_params)
    respond_to do |format|
      if @video.save
        format.html { redirect_to @video, notice: 'Video was successfully created.' }
        format.json { render :show, status: :created, location: @video }
      else
        format.html { render :new }
        format.json { render json: @video.errors, status: :unprocessable_entity }
      end
    end
  end
  # Likes video, increment likes count
  def like
    @video.like!
  end
  # Dislikes video, increment likes count
  def dislike
    @video.dislike!
  end
  private
  def set_video
    @video = Video.find(params[:id])
  end
  def video_params
    params.require(:video).permit(:video_file, :name)
  end
end

Quite straightforward, isn't it?

Now views again. Let's remove application.html.erb layout from app/views/layouts and create application.haml.

!!!
%html
  %head
    %title VideoShrimp
    = stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track' => true
    = stylesheet_link_tag    '//vjs.zencdn.net/5.0.2/video-js.css'
    = javascript_include_tag 'application', 'data-turbolinks-track' => true
    = javascript_include_tag '//cdn.pubnub.com/pubnub-dev.js'
    = csrf_meta_tags
  %body{'data-no-turbolink': true}
    - if current_user
      .navbar.navbar-default.navbar-fixed-top
        .container
          .navbar-header
            = link_to 'VideoShrimp', root_url, class: 'navbar-brand'
          %ul.nav.navbar-nav.navbar-right
            %li
              = link_to 'Browse videos', videos_path
            %li
              = link_to 'Upload video', new_video_path
            %li.dropdown
              %a.dropdown-toggle{"aria-expanded" => "false", "aria-haspopup" => "true", "data-toggle" => "dropdown", :href => "#", :role => "button"}
                = current_user.email
                %span.caret
              %ul.dropdown-menu
                %li
                  = link_to 'Profile', current_user
                %li
                  = link_to 'Edit profile', edit_user_path(current_user)
                %li.divider{:role => "separator"}
                %li
                  = link_to 'Log out', destroy_user_session_path, :method => :delete
            %li#user-notifications.dropdown{"data-pn-auth-key": current_user.pn_auth_key, "data-pn-notification-channel": current_user.notification_channel}
              %a.dropdown-toggle{"aria-expanded" => "false", "aria-haspopup" => "true", "data-toggle" => "dropdown", :href => "#", :role => "button"}
                %span.glyphicon.glyphicon-bell
              %ul.dropdown-menu
    = yield

That's empty layout with some basic bootstrapped top navigation. There're also tags for pubnub that we will use for notifications and videojs for video player.

Let's add bootstrap to stylesheets!
First, remove app/assets/stylesheets/application.css and create app/assets/stylesheets/application.scss with:

@import "bootstrap-sprockets";
@import "bootstrap";
@import "global";
@import "video";

Create global.scss and video.scss too.

Bootstrap needs to be added to javascript file app/assets/javascripts/applications.js alos. So it should look like:

//= require jquery
//= require jquery_ujs
//= require turbolinks
//= require bootstrap
//= require_tree .

Last one small thing to do in assets is to edit global.scss file under app/assets/stylesheets/ and add there:

body {
  padding-top: 60px;
}

Thanks to that webpage content won't hide under top navigation.

All of this stuff will won't work of course because we haven't created routes yet. So let's do it and edit config/routes.rb to look like:

require 'sidekiq/web'
Rails.application.routes.draw do
  root 'videos#index'
  resources :videos
  get '/videos/:id/like' => 'videos#like'
  get '/videos/:id/dislike' => 'videos#dislike'
  devise_for :users
  resources :users
  mount Sidekiq::Web => '/sidekiq'
end

So, home page of our application will be list of uploaded videos. Making resources for videos and users is a bit overkill because we won't be using part of routes that are created thanks to that but if you would like to expand application that we're creating you will defienetely need it.
Sidekiq web it's just web interface for sidekiq - just nice stuff to have. Don't miss require 'sidekiq/web' on top of the file.

At least the rest of views, some form etc.

Let's start with user. Under app/views/users/ let's create two files:
show.haml

.container
  .row
    .col-md-12
      %h2= @user.email
.container
  .row
    - @user.videos.each do |video|
      .col-md-3.thumb.video-thumb{ 'data-video-id': video.id }
        .likes
          %span.likes-count= video.likes
          %span.glyphicon.glyphicon-heart
        = link_to video, class: 'thumbnail' do
          = image_tag video.thumbnail.url(:medium_nr)

Yes, that's user profile. Yes, there is not a lot of things.

edit.haml

.container
  .row
    .col-md-6.col-sm-12
      %h2 Edit profile
      = simple_form_for @user do |f|
        = f.input :email
        = f.button :submit, class: 'btn-primary', value: 'Update Profile'

Now let's create video views, put them in app/views/videos
index.haml

.container
  .row
    - @videos.each do |video|
      .col-md-3.thumb.video-thumb{ 'data-video-id': video.id }
        .likes
          %span.likes-count= video.likes
          %span.glyphicon.glyphicon-heart
        = link_to video, class: 'thumbnail' do
          = image_tag video.thumbnail.url(:medium_nr)
  .row
    .col-md-12
      .pull-right
        = link_to 'Upload new video', new_video_url, class: 'btn btn-primary'

It will render list of videos' thumbnails, three in a row. Every thumbnail has data-video-id property that we will use later. There's also likes counter on each video.

show.haml

.container
  .row.video-full{ 'data-video-id': @video.id }
    .col-md-10
      %h1= @video.name
      %p.small
        = link_to 'Back to videos' ,videos_path
      - if @video.all_formats_encoded?
        %video#my-video.video-js{:controls => "", "data-setup" => "{}", :height => "264", :preload => "auto", :width => "640"}
          %source{:src => @video.mp4_file.url, :type => "video/mp4"}
          %source{:src => @video.webm_file.url, :type => "video/webm"}
          %source{:src => @video.ogg_file.url, :type => "video/ogg"}
          %p.vjs-no-js
            To view this video please enable JavaScript, and consider upgrading to a web browser that
            %a{:href => "http://videojs.com/html5-video-support/", :target => "_blank"} supports HTML5 video
      - else
        %p Video is still being encoded.
    .col-md-2
      %h1
        %span.likes-count= @video.likes
        %span.glyphicon.glyphicon-heart

Displays video and allows us to like or dislike. It doesn't update counter because we will be using pubnub notifications to do that. Anyway, in non-POC application optimistic likes update would be good thing to do here.

new.haml

.container
  .row
    .col-md-6.col-sm-12
      %h2 Upload new video
      = simple_form_for @video, html: { multipart: true } do |f|
        = f.input :name
        = f.input :video_file, as: :file
        = f.button :submit, class: 'btn-primary', value: 'Upload Video'

Simple form to upload video. Give it a name and pass a file.

Congratulations! You have done some stuff already!

Video Encoding and Notifications

So, now we need to encode uploaded videos, show them to user and send notifications. Let's setup pubnub to do that.

Head to Pubnub website and create new account. After creating new account you should add new app and generate keys for these app. We will use Storeage & Playback feature for notifications history and Access Manager to make private notifications private.

You will need to copy your keys to config/secrets.yml as pubnub_subscribe_key, pubnub_publish_key, pubnub_secret_key and you should create by yourself some unique pubnub_auth_key for server.

Now we need to add pubnub.rb under config/initializers, that code will run while application is starting.

pubnub.rb

# Initialize pubnub client with our keys
$pubnub = Pubnub.new(
    subscribe_key: Rails.application.secrets.pubnub_subscribe_key,
    publish_key: Rails.application.secrets.pubnub_publish_key,
    secret_key: Rails.application.secrets.pubnub_secret_key,
    auth_key: Rails.application.secrets.pubnub_auth_key
)
# As we have PAM enabled, we have to grant access to channels.
# That grants read right to any channel that begins with 'video.' to everyone.
$pubnub.grant(
    read: true,
    write: false,
    auth_key: nil,
    channel: 'video.*',
    http_sync: true,
    ttl: 0
)
# That grants read and write right to any channel that begins with 'video.' to this client.
$pubnub.grant(
    read: true,
    write: true,
    auth_key: Rails.application.secrets.pubnub_auth_key,
    channel: 'video.*',
    http_sync: true,
    ttl: 0
)
# That grants read and write right to any channel that begins with 'notifications.' to this client.
$pubnub.grant(
    read: true,
    write: true,
    auth_key: Rails.application.secrets.pubnub_auth_key,
    channel: 'notifications.*',
    http_sync: true,
    ttl: 0
)

As you can see, after initializing $pubnub global variable we're running three grants with ttl: 0 - which indicates that the grant will never expire.

Next, we have to give user possibility to read from his personal notifications channel. We will do that by creating unique auth_key for every user and grants him read right to his notification channel. Let's generate migration:

rails generate migration add_pn_auth_key_to_users

Edit created migration to look like:

class AddPnAuthKeyToUsers < ActiveRecord::Migration
  def change
    add_column :users, :pn_auth_key, :string
  end
end

Now, edit user.rb model and add after devise:

after_create :gen_auth_and_grant_perms
def notification_channel
  "notifications.#{self.id}"
end
def gen_auth_and_grant_perms
  generate_pn_auth!
  $pubnub.grant(
    channel: notification_channel,
    auth_key: pn_auth_key,
    ttl: 0,
    http_sync: true
  )
end
def generate_pn_auth
  self.pn_auth_key = SecureRandom.hex
end
def generate_pn_auth!
  self.generate_pn_auth
  save
end

That will run gen_auth_and_grant_perms method after user is created. User will receive his unique auth_key that will be used by javascript client and access to read on his private channel.

Now we will update Video model. Edit video.rb and make changes in publish! like! and dislike! methods.

# Publish video makes it available
def publish!
  self.published = true
  save
  $pubnub.publish(channel: "video.#{id}", message: {event: :published}, http_sync: true)
  $pubnub.publish(channel: self.user.notification_channel, message: {event: :published, scope: :videos, id: self.id, name: name.truncate(20)}, http_sync: true)
end
# Increment likes counter
def like!
  self.likes += 1
  save
  $pubnub.publish(channel: "video.#{id}", message: {event: :liked}, http_sync: true)
end
# Decrease likes counter
def dislike!
  self.likes -= 1
  save
  $pubnub.publish(channel: "video.#{id}", message: {event: :disliked}, http_sync: true)
end

Great! Now every like and dislike sends message to corresponding video channel so we can live update our frontend when subscribed to given channel. publish! will send notification to owner and notification that video has been published on corresponding video channel.

Before working on frontend we need to write workers that will encode freshly uploaded video. Let's create app/workers directory. Inside it we need to create several files:

mp4_video_encoder.rb

class Mp4VideoEncoder
  include Sidekiq::Worker
  def perform(video_id)
    video = Video.find(video_id)
    path = video.video_file.path
    output = "/tmp/#{Time.now.getutc.to_f.to_s.delete('.')}.mp4"
    _command = `ffmpeg -i #{path} -f mp4 -vcodec h264 -acodec aac -strict -2 #{output}`
    if $?.to_i == 0
      video.mp4_file = File.open(output, 'r')
      video.save
      FileUtils.rm(output)
    else
      raise $?
    end
  end
end

As you can see it's simple script which retrieves video from db by it's id, generates random output path and runs shell command to encode original file into mp4 format. If shell command finished with success video is updated with new file, saved and temporary file produced by ffmpeg is deleted.

Two next files are almost the same, if you want be more DRY you can write own module that encodes passed video to passed format and include that module in workers to use. Anyway, two next files:

ogv_video_encoder.rb

class OgvVideoEncoder
  include Sidekiq::Worker
  def perform(video_id)
    video = Video.find(video_id)
    path = video.video_file.path
    output = "/tmp/#{Time.now.getutc.to_f.to_s.delete('.')}.ogv"
    _command = `ffmpeg -i #{path} -codec:v libtheora -qscale:v 7 -codec:a libvorbis -qscale:a 7 #{output}`
    if $?.to_i == 0
      video.ogg_file = File.open(output, 'r')
      video.save
      FileUtils.rm(output)
    else
      raise $?
    end
  end
end

and webm_video_encoder.rb

class WebmVideoEncoder
  include Sidekiq::Worker
  def perform(video_id)
    video = Video.find(video_id)
    path = video.video_file.path
    output = "/tmp/#{Time.now.getutc.to_f.to_s.delete('.')}.webm"
    _command = `ffmpeg -i #{path} -f webm -c:v libvpx -b:v 1M -c:a libvorbis #{output}`
    if $?.to_i == 0
      video.webm_file = File.open(output, 'r')
      video.save
      FileUtils.rm(output)
    else
      raise $?
    end
  end
end

The third one file will take one frame at 00:01:00 time of video and save as video thumbnail.

thumbnail_cutter.rb

class ThumbnailCutter
  include Sidekiq::Worker
  def perform(video_id)
    video = Video.find(video_id)
    output = "/tmp/#{Time.now.getutc.to_f.to_s.delete('.')}.png"
    _command = `ffmpeg -i #{video.video_file.path} -ss 00:00:01.000 -vframes 1 #{output}`
    if $?.to_i == 0
      video.thumbnail = File.open(output, 'r')
      video.save
      FileUtils.rm(output)
    else
      raise $?
    end
  end
end

Great! From here you need to fire sidekiq together with rails server. You can do it by typing bundle exec sidekiq in console.

When we have workers we would like to fire that workers immediately after video is uploaded so let's edit our Video model and add:

after_create :run_encoders
private
def run_encoders
  ThumbnailCutter.perform_async(self.id)
  Mp4VideoEncoder.perform_async(self.id)
  OgvVideoEncoder.perform_async(self.id)
  WebmVideoEncoder.perform_async(self.id)
end

There's still one thing missing. Uploaded video still isn't published! Now we will create reoccurring worker that will search for any non-published video and check if it's ready to be published. If yes, it will publish it and send notification. Create app/workers/video_publisher.rb with:

class VideoPublisher
  include Sidekiq::Worker
  include Sidetiq::Schedulable
  recurrence { minutely }
  def perform
    Video.where(published: false).each do |video|
      video.publish! if video.all_formats_encoded?
    end
  end
end

As you can see, there's some difference between this and previous workers.
include Sidetiq::Schedulable - makes that worker, well, schedulable.
reccurence { minutely } - makes that worker run every minute.

Notifications on Front-End

Create two files in app/assets/javascripts/:

notifications.js.coffee.erb

$ ->
  if $("#user-notifications").length
    auth_key = $("#user-notifications").attr("data-pn-auth-key")
    notification_channel = $("#user-notifications").attr('data-pn-notification-channel')
    add_notifications = (msg) ->
          for notification in msg[0]
              switch notification.event
                  when 'published'
                      notification_html  = "<li><a href='/" + notification.scope + "/" + notification.id + "'>"
                      notification_html += "Your video " + notification.name + " has been published"
                      notification_html += "</a></li>"
                      $("#user-notifications .dropdown-menu").prepend notification_html
    window.pubnub = PUBNUB.init
          subscribe_key: "<%= Rails.application.secrets.pubnub_subscribe_key %>",
          publish_key: "<%= Rails.application.secrets.pubnub_publish_key %>",
          auth_key: auth_key
    window.pubnub.history
        channel: notification_channel,
        count: 10,
        reverse: false,
        callback: (msg) ->
            add_notifications(msg)
    window.pubnub.subscribe
        channel: notification_channel,
        callback: (msg) ->
            add_notifications(msg)

That script runs after document is loaded and there's #user-notifications node in DOM. It initializes pubnub client with user auth_key. Loads previous ten notifications form user notifications channel and later subscribes to that channel waiting for new notifications.

And second file:
videos.coffee

$ ->
  for video in $('.video-full, .video-thumb')
    window.pubnub.subscribe
      channel: 'video.' + $(video).attr('data-video-id')
      message: (msg, env, chan) ->
        id = chan.split('.')[1]
        switch msg.event
          when 'published'
            location.reload()
          when 'liked'
            for likes in $("[data-video-id=" + id + "]").find('.likes-count')
              console.log('add')
              $(likes).html(parseInt($(likes).html()) + 1)
          when 'disliked'
            for likes in $("[data-video-id=" + id + "]").find('.likes-count')
              console.log('remove')
              $(likes).html(parseInt($(likes).html()) - 1)

That script subscribes to information channel about every video on page (We have two type of elements with videos. One has class video-full and second has class video-thumb, both of them havedata-video-id that is used to determine channel name to subscribe). When user is on video page that isn't published yet, he is subscribed to that non-published video channel, and when client receive message about video beeing published, it simply reload webpage. Two other events that can happen is like and dislike. As you can expect it searches for every occurence of video with given in channel name id and updates likes counter.

So, let's take a look at out application. When you fire rails server and sidekiq, you can head to localhost:3000. You will be welcome by sign in form. Let's choose sign up and create some new user. That's it! Feel free to play around your new prototype.

That's it. You've made video sharing app prototype. There's a lot stuff that can be added or changed here. For example loading more notification, marking point in time when user viewed notifications. Nicer video uploader. You can limit likes (one like per video per user). Add comments section that will be updated live thanks to PubNub. Or ever rewrite whole frontend to SPA, make own API for communication or push data thought PubNub.

You can get the full source to this application from the Github project.