From the server selection spec:

After a server is selected, several error conditions could still occur that make the selected server unsuitable for sending the operation, such as:

• the server could have shutdown the socket (e.g. a primary stepping down),
• a connection pool could be empty, requiring new connections; those connections could fail to connect or could fail the server handshake

This specification does not require nor prohibit drivers from attempting automatic recovery for various cases where it might be considered reasonable to do so, such as:

• repeating server selection if, after selection, a socket is determined to be unsuitable before a message is sent on it

Retrying server selection when a socket is determined to be unsuitable before a message is sent on it would minimize the chance that applications see "NotMasterError: not master" or "AutoReconnect: connection closed" errors.

This ticket is a reminder that this improvement is possible.