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
- 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.