NewSQLInstance returns a new Instance struct and starts its heartbeating loop.

Instance implements the sqlliveness.Instance interface by storing the liveness sessions in table system.sqlliveness and relying on a heart beat loop to extend the existing sessions' expirations or creating a new session to replace a session that has expired and deleted from the table.

SessionEventListener is an interface used by the Instance to notify listeners of some state changes.

Writer provides interactions with the storage of session records.