When only a log destination is selected that is not built-in (e.g. file, console) then log messages that occur before the module providing the logging sink do not go anywhere.
This is noticeable when only syslog logging is enabled, for example. Messages logged before mod_posix loads are not recorded.
A possible fix is to prioritize the module selected for logging (probably we would have to switch to e.g. a mod_log_syslog name format), and ensure it loads before anything else. Or to buffer messages from startup until the logging sink is ready.
Looked at various solutions for this issue. Ultimately decided to only support in-core log sinks. Therefore moved syslog sink from mod_posix to loggingmanager in 1460c4966262.
Were we going to deprecated non-core sinks or is it enough to list this problem in the docs?