Action Cable
So I heard you want to make your Rails application realtime...
First, Some Background
HTTP vs. WebSockets vs. Everything Else
HTTP = Hypertext Transfer Protocol
- GET, POST, DELETE, etc. are HTTP methods sent by clients
- A client sends a request, and the server sends a response
WebSockets
- Allows a bidirectional connection between client and server
- Both client and server can send and receive data in real time
- Created by HTTP connection being upgraded, then held open
Everything Else
- Short Polling - Client periodically sends repeated HTTP requests to the server
- Long Polling - Server holds open HTTP connections until new data is sent
- HTTP Streaming - Server holds open HTTP connection and sends data over one connection
- Server Sent Events - Client opens HTTP connection that can accept push notifications
Rails + Realtime
( Until Rails 5 = 💔 )
- ActionController::Streaming (sorry, wrong type of streaming)
- ActionController::Live + Server Sent Events
- Pusher, Faye, Node, etc.
But now, Action Cable
A fullstack WebSockets implementation built directly into Rails
- Create channels with classic Rails namespacing
- Broadcast data from anywhere within application
- Subscribe views to channels to pick up broadcasted data
- Retain flexibility but let Rails worry about connections
Let's see it in action!
( Demo )
So what's really behind the magic?
( The short version )
The Server
- Run separately or mounted as an engine
- Establishes pubsub connection (Redis or PostgreSQL)
- Creates an event loop that listens in the background
The Connection
- Client-side consumer creation initiates connection
- Consumer make a GET request to server and requests upgrade
- Server can authorize, identify, and/or accept connection
The Channel
- Channels are exposed to and called by the client
- Allows consumer subscription to actual pubsub channel
- Represents a stateless stream of data accessible to consumer
Questions?
Slides: http://hayleycanderson.github.io/action-cable-intro