This node is an arbiter (contains no data).
This node is connected.
This node is down.
This node encountered a fatal error.
This node has no state yet (never been reached by the driver).
This node is not connected.
This node is a primary (both read and write operations are allowed).
This node is recovering (initial syncing, post-rollback, stale members).
This node is the rollback state.
This node is a secondary (only read operations that are slaveOk are allowed).
This node is starting up (phase 2, forking threads).
This node is in an unknown state (it has never been reached from another node's point of view).
Gets the NodeState matching the given state code.