Specs

unreachable_nodes() :: %{required(node()) => unreachable_since}
when unreachable_since: pos_integer()

Gets information about nodes that are active but unreachable from Node.self().

RaftFleet periodically checks reachability to the other active nodes. This function retrieves results of the checks as a map. Each key of the returned map is a currently unreachable node (i.e. if there's no problem %{} is returned), whereas each value is a timestamp (seconds since epoch) at which the node was recognized as unreachable.

Note that returned timestamps are not so accurate about when the node failed, since they are obtained by healthchecks with an interval of :node_purge_reconnect_interval (see also RaftFleet.Config). Note also that, when a node remains unreachable for more than :node_purge_failure_time_window, the node will be automatically purged from the active nodes. After purging the failed node will not be included in return value of this function (as the node is no longer active).