Websocket Messaging Patterns

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Messaging Patterns + WebSockets

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Me • I write full stack javascript • I work at Fractal • I like to code • I love open source

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SOAP

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Just kidding

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Websocket? • Bidirectional • Always open • Less overhead than HTTP • Faster • Binary data • “Real-time web cloudscale 3.0”

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Browser Support Use shims

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Implementations • Socket.io • Engine.io • SockJS • ws

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RPC • Remote Procedure Call • Request-Response cycle

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Server Client Request Response Thinking…

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RPC History • Used to be a big deal for cross-process communication • REST/HTTP knocked it out of the game • WebSockets are bringing it back

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RPC – Use Cases • Scaling procedures horizontally • Replacement for REST over HTTP • Communicating between the client and server

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RPC – Example Sequence • Client sends request for procedure “hello” with arguments [“world”] • Server receives and unpacks message • Server calls procedure “hello” with arguments [“world”] • Server sends response with procedure return value • Client handles response

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RPC - Implementations • Vein • DNode • NowJS* • jsonrpc2

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PubSub • Client (subscriber) subscribes to a topic • Client (publisher) publishes a message about the topic without knowledge of subscribers • Similar to EventEmitter

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PubSub - Diagram

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PubSub – Use Cases • Chat • Watching realtime changes – Whiteboards – File collaboration – Auction/trading systems

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PubSub – Example Sequence • Subscribers (Client A and B) subscribe to channel “test” • Publisher (Client C) publishes message “hey” to channel “test” • Client A and B receive message “hey” on channel “test”

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PubSub - Implementations • Pulsar • Socket.io • PubNub (PubSub as a service)

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DSTM • Distributed Software Transactional Memory • Shared object between all clients • Changes to the shared object happen in “transactions” • Changes to the shared object are synchronized between all clients • Conflict resolution guarantees atomic transactions

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DSTM - Diagram Server Object Conflict Resolution Object Conflict Resolution Clients Clients

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DSTM – Use Cases • Data synchronization • Distributed/scalable systems • Financial transactions • Anything where accuracy is involved

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DSTM – Example Sequence • Client A connects and receives object • Client B connects and receives object • Client B changes key “hello” to “world” • Client A changes key “hello” to “code camp” • Transaction from Client A is rejected due to conflict – synchronization is forced • Client A retries it’s transaction

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DSTM – Implementations • Warlock • AtomizeJS

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“Fat Client” - The Philosophy • Lower server requirements • Working offline • Higher server capacity • Scales easily • Uses less bandwidth

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“Fat Client” – Example Sequence • Client A receives index.html which then loads all static resources • If Client A needs something from the server it is either work or message passing which can be done over WebSockets • After the initial grab of static files everything is done via WebSockets