Struct Registration 

struct Registration {
    tx: UnboundedSender<SeatUpdate>,
    role: SubscriberRole,
}

One subscriber’s end of the fan-out.

The channel is unbounded, and what bounds it instead is the connection. A bounded channel forces the sender to choose between blocking - which would hold every seat’s stream behind one slow reader, under this fan-out’s own lock - and dropping a frame, which rule 25 forbids. So the sender never waits, and the receiving connection drains continuously: a socket that stops accepting its frames is cut at WRITE_BOUND (60 s), so a subscriber that keeps up holds a batch’s worth and one that does not is disconnected rather than queued against forever. The per-frame weight is a pointer now, shared with the ring below rather than copied per subscriber.

Fields

tx: UnboundedSender<SeatUpdate>

role: SubscriberRole