Currently the only advice offered to monitor for errors and warnings in the MongoDB logs (for mongod, mongos and config server) is to search for the strings "error" and "warning". This tends to return too much information even when just using default verbosity for the logging and gives no indication of their criticality. Additionally much of the information returned is just noise rather than real warnings or errors (e.g. getlasterror messages).

There should be a standard format for errors and warnings which includes an indication of their criticality, e.g.:

ERROR-CRITICAL:
ERROR-MAJOR:
ERROR-MINOR:
WARNING:

This would greatly help with automated monitoring of the logs and enable a focus on the most critical issues and so a quicker response to fix issues.