[dm-devel] Thoughts about multipathd's log thread

[Martin Wilck]

(sending again, with dm-devel on cc. Sorry!)

Hi Ben, hi Christophe,

AFAIU, the purpose of the log thread is to avoid blocking while writing
log messages to the syslog socket. The thread has been in place for a
long time. However, the large majority of multipath installations today
runs on systemd-enabled systems, where we don't use the log thread.
Rather, we write to stderr (which is actually a journald socket)
directly.

That makes me wonder: if the problem of blocking while writing to the
log socket is real, it should happen with journald as well (possibly
more so than with syslogd; journald doesn't exactly have the reputation
of being highly efficient). Thus, we should be using the log thread
also for the systemd case. OTOH, I'm not aware of any bug reports
saying that multipathd wasn't able to handle events because of blocking
log calls. So perhaps the issue is rather theoretical? In that case, we
could do away with all the complexity the log thread involves.

What do you think?

Martin