heartbeat
abstract suspend fun heartbeat(service: String, node: String, address: String, ttl: Duration, groups: Set<String> = emptySet()): Member
Registers node as a member of service reachable at address, serving the lease groups, or keeps it one, for ttl from now. A later heartbeat replaces the address and the groups, so a node restarted on another address is found there, and one that stops taking part in a group drops it at once.