Volt includes a message bus interface which provides a pub/sub interface between all volt instances (server, console, runner, etc..) inside a volt cluster (any instance connected to the same database) Volt ships with a PeerToPeer message bus, but you can create or use other message bus's.
The message bus is used internally in volt to push model updates between instances. The updates can then be sent to any browsers connected to the volt instance. This allows Volt to easily scale out horizontally while keeping live update push support.
The default peer to peer bus uses the database to sync a list of ip's and ports for socket servers that the instances can setup. (See the generated config/app.rb code for configuration details) As long as the servers can talk to each other over the network, everything should just work™. (In many deployment situations, servers can talk between each other in a private cloud) If the servers only have some ports exposed, you can specify the available ports in config/app.rb
The message bus can also be used from your app's code. The message bus provides a subscribe and publish method.
TODO: need to add more docs for using the message bus
You can create your own message bus implementation by implementing the BaseMessageBus class at lib/volt/message_bus/base_message_bus.rb Then you can set the config.message_bus.bus_name = 'name_of_class' where name_of_class is the underscored version of you class name. See base_message_bus.rb for details on implementing your own bus.