The circuit provides two special element types @join and @leave,
called subscriptions. Their job is to notify you when new
circuit servers join the systems or others leave it.
Both of them behave like receive-only channels.
circuit mk@join /X88550014d4c82e4d/watch/join circuit mk@leave /X88550014d4c82e4d/watch/leave
The join subscription delivers a new message each time a cicruit server joins the system. The received message holds the anchor path of the new server.
circuit recv /X88550014d4c82e4d/watch/join
Similarly, the leave subscription delivers a new message each time a circuit server disappears from the system.
circuit peek /X88550014d4c82e4d/watch/join