How to send the correct PID in forking service? #101
Description
When initializing Formatter3164 or Formatter5424 I have to provide a fixed PID, or let the defaults use the current PID (which is then also fixed from there). This creates a problem for services that fork after initializing logging (in my case to put the process into the background, would also apply to services that fork for parallel processing): Any log messages written after forking will log an incorrect PID.
The documentation example sets the PID to 0, and I've seen systemd-journald replace it with the actual PID of the sending process, but not all syslog implementations do that, or could be patched to (getting the PID from a unix socket client should work, from a TCP/UDP socket not so much).
The log crate documentation says that log::set_logger/log::set_boxed_logger may only be called once, so reinitializing it after forking is not an option. Initializing logging after forking would mean I can't send errors that occur before to syslog.
Am I missing some way to use the current PID at the time a log message is written, or update the formatter PID when forking? Or if not, could you add one?