Minimalistic Publish/Subscribe for SockJS and sockjs-erlang

• No history or persistance, for realtime messaging only
• No manual channel creation, if nobody is subscribed - message just discards

sps:start().
sps:subscribe(Channel, Conn).
sps:unsubscribe(Channel, Conn).
sps:publish(Channel, Message).

• Channel - arbitrary binary string
• Conn and Message - as in SockJS

• On each node application starts 24 managers (locally registered gen_servers with predefined names) under 1 supervisor.
• Binary channels are mapped to respective manager with hash function (zlib:crc2/2).
• On subscribe/unsubscribe Conn is passed to local manager to be stored in ETS table. Each channel has it's own unnamed table. Table ids are looked up via private ETS master-table.
• On publish Message is broadcasted to respective manager on each connected erlang node with gen_server:abcast/2. Manager determines table id for channel and spawns short-lived process that will JSON-encode it and broadcast to all connections in channel ETS table. If this process stumbles upon dead connection it removes it.
• Optional deflate message support (in sps:subscribe/3 specify third argument, Deflate, as true). To decode on client side you need to apply base64:decode followed by zlib inflate.

• RabbitMQ - separate message passing service with advanced features like clustering, persistance and acknowledgements. Recommended if messages are important and shouldn't be lost.
• Distributed Pub/Sub - simple publish/subscribe with message history and asynchronous replication between Erlang nodes.
• sockjs-multiplex - part of sockjs-erlang that can do something similar with predefined channels and customized handlers, only within one Erlang node.