For drawing a map. nodes holds one entry per service per machine, named host/service; edges say which talks to which, with a kind of proxy, http, mail or dns; hosts groups the same entries under the machine they run on. The connections come from where the proxies say they pass traffic, plus a fixed list of the calls the services make to each other.
Good to know
A service is healthy when it is running and its machine checked in within the last heartbeat_stale_after_sec seconds; a machine past that is marked stale.
A service found only as somewhere a proxy passes traffic, on a machine with no agent, has monitored false and healthy null.
