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chrismccord
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Real-time Rails Partials

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RenderSync Build Status Code climate Code coverage gem version

This started as a thought experiment that is growing into a viable option for realtime Rails apps without ditching the standard rails stack that we love and are so productive with for a heavy client side MVC framework.

Real-time partials with Rails. Sync lets you render partials for models that, with minimal code, update in realtime in the browser when changes occur on the server.

Watch a screencast to see it in action

See it in action

In practice, one simply only needs to replace:


with:


Then update views realtime automatically with the

sync
DSL or with a simple
sync_update(@user)
in the controller without any extra javascript or configuration.

In addition to real-time updates, Sync also provides:

  • Realtime removal of partials from the DOM when the sync'd model is destroyed in the controller via
    sync_destroy(@user)
  • Realtime appending of newly created model's on scoped channels
  • JavaScript/CoffeeScript hooks to override and extend element updates/appends/removes for partials
  • Support for Faye and Pusher

Requirements

  • Ruby >= 1.9.3
  • Rails 3 >= 3.1 or Rails 4
  • jQuery >= 1.9

Upgrading from 0.4.0

The gem name has changed from

sync
to
render_sync
, so to upgrade you just need to use the new name in your Gemfile:
gem 'render_sync'

Installation

1) Add the gem to your
Gemfile

Using Faye

gem 'faye'
gem 'thin', require: false
gem 'render_sync'

Using Pusher

gem 'pusher'
gem 'render_sync'

Install

$ bundle
$ rails g render_sync:install

2) Require sync in your asset javascript manifest
app/assets/javascripts/application.js
:

//= require sync

3) Add sync's configuration script to your application layout
app/views/layouts/application.html.erb


4) Configure your pubsub server (Faye or Pusher)

Using Faye (self hosted)

Set your configuration in the generated

config/sync.yml
file, using the Faye adapter. Then run Faye alongside your app.
rackup sync.ru -E production

Using Pusher (SaaS)

Set your configuration in the generated

config/sync.yml
file, using the Pusher adapter. No extra process/setup.

Current Caveats

The current implementation uses a DOM range query (jQuery's

nextUntil
) to match your partial's "element" in the DOM. The way this selector works requires your sync'd partial to be wrapped in a root level html tag for that partial file. For example, this parent view/sync partial approach would not work:

Given the sync partial

_todo_row.html.erb
:
Title:

And the parent view:

</tr>
The markup would need to change to:

sync partial

_todo_row.html.erb
:
 
  Title:


And the parent view changed to:

I'm currently investigating true DOM ranges via the Range object.

'Automatic' syncing through the sync model DSL

In addition to calling explicit sync actions within controller methods, a

sync
and
enable_sync
DSL has been added to ActionController::Base and ActiveRecord::Base to automate the syncing approach in a controlled, threadsafe way.

Example Model/Controller

  class Todo < ActiveRecord::Base
    sync :all
  end
  class TodosController < ApplicationController
    enable_sync only: [:create, :update, :destroy]
    ...
  end

Now, whenever a Todo is created/updated/destroyed inside an action of the

TodosController
changes are automatically pushed to all subscribed clients without manually calling sync actions.

Updating multiple sets of records with sync scopes

Sometimes you might want to display multiple differently scoped todo lists throughout your application and keep them all in sync. For example:

  • A global list with all todos
  • A list with all completed todos
  • A list with all todos of a user
  • A list with all todos of a project
  • ...

This was quite tricky to accomplish in previous versions of sync. Well, now this is going to be dead simple with the help of explicit sync scopes. First, define your desired sync scopes on the model with

sync_scope
like this:
class Todo < ActiveRecord::Base
  belongs_to :user
  belongs_to :project

sync :all

sync_scope :active, -> { where(completed: false) } sync_scope :completed, -> { where(completed: true) } end

Then in your views display the different sets of todos by passing the

scope
as a parameter like this:

Now, whenever a todo is created/updated/destroyed sync will push the appropriate changes to all affected clients. This also works for attribute changes that concern the belonging to a specific scope itself. E.g. if the

completed
flag is set to
true
during an update action sync will automatically push the todo partial to all clients displaying the list of completed todos and remove it from all clients subscribed to the list of active todos.

Advanced scoping with parameters

In order to display lists that are dynamically scoped (e.g. by the

current_user
or a
@project
instance variable) you can setup dynamic sync scopes like this:
sync_scope :by_user, ->(user) { where(user_id: user.id) }
sync_scope :by_project, ->(project) { where(project_id: project.id) }

Note that the naming of the parameters is very important for sync to do its magic. Be sure to only use names of methods, parent associations or ActiveRecord attributes defined on the model (e.g. in this case

user
and
project
). This way sync will be able to detect changes to the scope.

Setup the rendering of the partials in the views with:

Beware that chaining of sync scopes in the view is currently not supported. So the following example would not work as expected:


To work around this just create an explicit sync_scope for your use case:

sync_scope :completed_by_user, ->(user) { completed.by_user(current_user) }

Things to keep in mind when using
sync_scope

Please keep in mind that the more sync scopes you set up the more sync messages will be send over your pubsub adapter. So be sure to keep the number scopes small and remove scopes you are not using.

Automatic updating of parent associations

If you want to automatically sync the partials of a parent association whenever a record changes you can use the

sync_touch
method. E.g. if you always want to sync the partials of the associated
user
and
project
just add this line to your
Todo
class:
sync_touch :project, :user

Syncing outside of the controller

Sync::Actions
can be included into any object wishing to perform sync publishes for a given resource. Instead of using the controller as context for rendering, a Sync::Renderer instance is used. Since the Renderer is not part of the request/response/session, it has no knowledge of the current session (ie. current_user), so syncing from outside the controller context will require some care that the partial can be rendered within a sessionless context.

Example Syncing from a background worker or rails console

class MyJob
  include Sync::Actions

def perform Sync::Model.enable do Todo.first.update title: "This todo will be sync'd on save" end Todo.first.update title: "This todo will NOT be sync'd on save"

Sync::Model.enable!
Todo.first.update title: "This todo will be sync'd on save"
Todo.first.update title: "This todo will be sync'd on save"
Todo.first.update title: "This todo will be sync'd on save"
Sync::Model.disable!
Todo.first.update title: "This todo will NOT be sync'd on save"

end end

Custom Sync Views and javascript hooks

Sync allows you to hook into and override or extend all of the actions it performs when updating partials on the client side. When a sync partial is rendered, sync will instantiate a javascript View class based on the following order of lookup:

  1. The camelized version of the concatenated snake case resource and partial names.
  2. The camelized version of the snake cased partial name.

Examples

partial name 'list_row', resource name 'todo', order of lookup:

  1. Sync.TodoListRow
  2. Sync.ListRow
  3. Sync.View (Default fallback)

For example, if you wanted to fade in/out a row in a sync'd todo list instead of the Sync.View default of instant insert/remove:

class Sync.TodoListRow extends Sync.View

beforeInsert: ($el) -> $el.hide() @insert($el)

afterInsert: -> @$el.fadeIn 'slow'

beforeRemove: -> @$el.fadeOut 'slow', => @remove()

Narrowing sync_new scope

Sometimes, you do not want your page to update with every new record. With the

scope
option, you can limit what is being updated on a given page.

One way of using

scope
is by supplying a String or a Symbol. This is useful for example when you want to only show new records for a given locale:

View:

erb

Controller/Model:

ruby
sync_new @todo, scope: @todo.locale

Another use of

scope
is with a parent resource. This way you can for example update a project page with new todos for this single project:

View:

erb

Controller/Model:

ruby
sync_new @todo, scope: @project

Both approaches can be combined. Just supply an Array of Strings/Symbols and/or parent resources to the

scope
option. Note that the order of elements matters. Be sure to use the same order in your view and in your controller/model.

Scoping by Partial

If a single resource has a bunch of different sync partials, calling

sync_new
or
sync_update
could be very expensive, as sync would need to render each partial for that resource, even if only one partial would be affected by the update. Because of this, sync allows you to scope these by the name of the partial:
def UsersController < ApplicationController
  …
  def create
    …
    if @user.save
      sync_new @user, partial: 'users_count'
    end
    …
  end
end

In the above example, only the

sync/users/users_count
partial will be rendered and pushed to subscribed clients.

Refetching Partials

Refetching allows syncing partials across different users when the partial requires the session's context (ie. current_user).

Ex: View: Add

refetch: true
to sync calls, and place partial file in a 'refetch' subdirectory in the model's sync view folder:

The partial file would be located in

app/views/sync/todos/refetch/_list_row.html.erb
erb




Notes

While this approach works very well for the cases it's needed, syncing without refetching should be used unless refetching is absolutely necessary for performance reasons. For example,

A sync update request is triggered on the server for a 'regular' sync'd partial with 100 listening clients: - number of http requests 1 - number of renders 1, pushed out to all 100 clients via pubsub server.

A sync update request is triggered on the server for a 'refetch' sync'd partial with 100 listening clients: - number of http requests 100 - number of renders 100, rendering each request in clients session context.

Using with cache_digests (Russian doll caching)

Sync has a custom

DependencyTracker::ERBTracker
that can handle
sync
render calls. Because the full partial name is not included, it has to guess the location of your partial based on the name of the
resource
or
collection
passed to it. See the tests to see how it works. If it doesn't work for you, you can always use the explicit "Template Dependency" markers.

To enable, add to

config/initializers/cache_digests.rb
:

Rails 4

require 'action_view/dependency_tracker'

ActionView::DependencyTracker.register_tracker :haml, Sync::ERBTracker ActionView::DependencyTracker.register_tracker :erb, Sync::ERBTracker

Rails 3 with cache_digests gem

require 'cache_digests/dependency_tracker'

CacheDigests::DependencyTracker.register_tracker :haml, Sync::ERBTracker CacheDigests::DependencyTracker.register_tracker :erb, Sync::ERBTracker

Note: haml support is limited, but it seems to work in most cases.

Serving Faye over HTTPS (with Thin)

Create a thin configuration file

config/sync_thin.yml
similar to the following:
---
port: 4443
ssl: true
ssl_key_file: /path/to/server.pem
ssl_cert_file: /path/to/certificate_chain.pem
environment: production
rackup: sync.ru

The

certificate_chain.pem
file should contain your signed certificate, followed by intermediate certificates (if any) and the root certificate of the CA that signed the key.

Next reconfigure the

server
and
adapter_javascript_url
in
config/sync.yml
to look like
https://your.hostname.com:4443/faye
and
https://your.hostname.com:4443/faye/faye.js
respectively.

Finally start up Thin from the project root.

thin -C config/sync_thin.yml start

Brief Example or checkout an example application

View

sync/users/_user_list_row.html.erb
  
  
  

View

users/index.html.erb

Some Users

Controller

def UsersController < ApplicationController
  …
  def create
    @user = User.new(user_params)
    if @user.save
      sync_new @user
    end
    respond_to do |format|
      format.html { redirect_to users_url }
      format.json { head :no_content }
    end
  end

def update @user = User.find(params[:id]) if user.save … end

# Sync updates to any partials listening for this user
sync_update @user

redirect_to users_path, notice: "Saved!"

end

def destroy @user = User.find(params[:id]) @user.destroy

# Sync destroy, telling client to remove all dom elements containing this user
sync_destroy @user

respond_to do |format|
  format.html { redirect_to users_url }
  format.json { head :no_content }
end

end end

Google detecting not found errors

If you're using Google Webmaster Tools you may notice that Google detects lots of URLs it can't find on your site when using Sync. This is because Google now attempts to discover URLs in JavaScript and some JavaScript we generate looks a little like a URL to Google. You can safely ignore this problem.

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