When the wrong user/pass is given, the driver should throw an exception right away without waiting for the default 30 second Connection Timeout. This used to work correctly in 1.7.* drivers and when we upgraded to 1.8 drivers the behavior has changed.

The exception that gets thrown is the generic MongoConnectionException that says "Unable to connect in the specified timeframe of '00:00:30'"

I'm not sure if the driver is continuously trying for 30 seconds but it would be nice if it can throw right away like it used to.