generate a warning during config parsing for potentially blocking operations

[anirbans]

When a large timeout value is set for the action queue and rsyslog is configured to forward logs to a remote server using TCP, it can lead to lockups and blocking of critical processes when the remote server becomes unavailable for a long time. The default value of the timeout has been reduced to 50 ms for the action queue but it can always be configured to have a higher value using the rsyslog config file. The default value of the timeout for the main queue is already high at 2 sec.

rsyslog should generate a warning when any user overrides the default timeout of the action queue and configures it with a high value of the order of few thousand milliseconds. ssh and other critical processes can block resulting in system wide lockups. This has also been reported by other users.

This ticket is raised to implement the warning capability into rsyslog during configuration parsing when such unsafe values are configured.

This applies to all versions of rsyslog but primarily for rsyslog v8.