SocketIO

SocketIO v2 is used for sending updates from Flamenco Manager to the web frontend. Version 2 of the protocol was chosen, because that has a mature Go server implementation readily available.

SocketIO messages have an event name and room name.

Web interface clients send messages to the server with just an event name. These are received in handlers set up by internal/manager/eventbus/socketio.go, function registerSIOEventHandlers().
Manager typically sends to all clients in a specific room. Which client has joined which room is determined by the Manager as well. By default every client joins the “job updates” and “chat” rooms. This is done in the OnConnection handler defined in registerSIOEventHandlers(). Clients can send messages to the Manager to change which rooms they are in.
Received messages (regardless of by whom) are handled based only on their event name. The room name only determines which client receives those messages.

Technical Details

The following files & directories are relevant to the SocketIO/MQTT broadcasting system on the Manager/backend side:

internal/manager/eventbus: package for the event broadcasting system, including implementations for SocketIO and MQTT.
pkg/api/flamenco-openapi.yaml: the OpenAPI specification also includes the structures sent over SocketIO and MQTT. Search for EventJobUpdate; the rest is defined in its vicinity.

For a relatively simple example of a job update broadcast, see func (f *Flamenco) SetJobPriority(...) in internal/manager/api_impl/jobs.go.