Modern Websocket Gateway Server
Problems
Real-Time Push Notifications
Chats
Games
Remote Procedure Calls (RPC)
Classic Web
Adding WS 1
Adding WS 2
Cons.
Message loss
Scaling/failover issues
Software upgrade issues
Custom routing
Introducing Swindon
A modern HTTP edge server
with smart websocket support
Swindon
A (reverse) proxy
Serves files (just in case)
Websockets
Basic Picture
Recall: WS 1
Basic Picture Again
Recall: WS 2
Key Points
Routing
Replication
Data Model
Software Updates (*)
WS Proto
RPC
Pub-Sub
Lattice
RPC
user1 → ☂: call chat.send_message(x)
☂ → backend1: chat.send_message("user1", x)
backend1 → ☂: return "ok"
☂ → user1: return "ok"
Routing
chat.* → chat{1,2,3}
pizza.* → pizza{1,2}
RPC Features
Prefix Routing
Sticky Auth
Pub-Sub
user1 → backend: I want room "kittens"
backend → ☂: subscribe(user1, @rooms.kittens)
user1 → backend: Send "hello"
backend → ☂: send(@rooms.kittens, "user1: hello")
☂ vs WAMP
WAMP: subscription from client
Swindon ☂: subscription from backend
(*) Web Application Messaging Protocol
Pub-Sub
Authorization
First time sync
Lattice
The Task
Components
Room List
Unread Messages
Chat History
Issues
Multiple tabs/devices
Eventual consistentcy
Lost/duplicate messages
Eventual Consistency
user1 -> messages read
user2 -> new message
Eventual Consistency
user1 -> -1 unread
user2 -> +1 message
Pub-Sub
Consistency2
device1 -> get_rooms
device2 -> add_room
Consistency3
device1 -> get_rooms
user2 -> new mesage
device2 -> add_room
user3 -> new mesage
CRDT
Commutative Replicated Data Types
CRDT
Solves eventual consistency problem
CRDT
Counter/Max
Counters
Game: Experience
Chat: Last Message Id
Metadata Version
CRDT: Money
Two ever growing counters:
Earned Money
Spent Money
Unread Messages
Total Messages
Last Read No.
Lattice
Lattice Birdview
Lattice CRDT
Lattice Values
Lattice
Auto-updates room list
Conflict-free eventual consistency
Simple to Run
swindon-dev ./public /api/=http://localhost:8111
Q & A
cargo install swindon