DRIVERS-2516 : If a driver has not started implementing logging yet, this ticket could be closed in favor of the original tickets around implementing the logging spec and adding log messages for other specs. All possible changes required by this ticket are captured in the text of the relevant specs. Drivers who have already implemented or are in the process of implementing logging should review the changes in this commit and ensure their implementations comply. To summarize what changed: For command log messages, when the user does not specify a port for a host and is therefore relying on the default 27017, the driver SHOULD include that default in log messages. The suggested unstructured representations for command log messages have been slightly modified to match the CMAP log messages. It's no longer a strict requirement that drivers support logging directly to a file. Instead, it is sufficient to provide a straightforward API that would allow a user to direct log messages to a file. Clarify that drivers MAY attempt to warn users about invalid values of environment variables, but MUST NOT throw an error. Require that if a driver supports configuring logging both via environment variables and programmatically, the programmatic configuration should take precedence. Rationale sections were added for the previous two bullet points.