RFC w.r.t. toggling debugging on/off for mountd via a signal

[Alan Somers]

On Sat, May 18, 2019 at 7:59 PM Rick Macklem <rmacklem at uoguelph.ca> wrote:
>
> Hi,
>
> I've been working with Peter Errikson on a patch for mountd that adds a new option
> for incremental updating of exports. This seems to be helping a lot w.r.t. performance
> on an NFS server with lots (10000+) of exported file systems.
>
> I have debug syslog() calls in the code, which I/Peter think would be worth keeping
> in the production code in case someone runs into problems with this new option.
>
> As such, I'd like to have the code compiled in by default (not only if DEBUG is defined,
> as mountd.c has now). I also was thinking it would be nice if the daemon didn't need
> to be restarted to enable/disable the debugging output, since that breaks NFS
> mounting during the restart.
>
> So, I was thinking of having the debugging output toggled on/off via SIGUSR1.
>
> What do you think of this idea?
> Any other/better ways to do this?
> Also, would LOG_DAEMON and LOG_DEBUG sound like the correct facility and
> priority for theses syslog() calls?
>
> Thanks in advance for any comments, rick

If the debug messages aren't so verbose that they'll slow down
syslogd, then you can just leave them enabled all the time.  syslogd
will filter them.  However, if they're super-verbose then SIGUSR1
sounds reasonable.  I can't think of another daemon with runtime
selectable logging verbosity like that.

-Alan