PID file ... not readable (yet?)

[Russ Allbery]

Benjamin Kaduk <kaduk at mit.edu> writes:

> I suspect that we would be a little friendlier to systemd if we passed
> -n to krb5kdc and adjusted the unit file accordingly.  There would still
> be a race window between when systemd thinks krb5kdc is started and
> ready to accept connections and when that is actually the case, but in
> both cases that window is small, and we cannot eliminate it entirely
> without patching the code to call systemd-specific functions.

For what it's worth, that's a pretty light burden.  It's just the
following Autoconf probe:

PKG_CHECK_EXISTS([libsystemd],
    [PKG_CHECK_MODULES([SYSTEMD], [libsystemd])
     AC_DEFINE([HAVE_SD_NOTIFY], 1, [Define if sd_notify is available.])])

(does require the pkg-config Autoconf stuff as well), the following at the
start of the daemon C file:

#ifdef HAVE_SD_NOTIFY
# include <systemd/sd-daemon.h>
#else
# define sd_notify(u, s)  0
#endif

and then just the following call when the daemon has started up and is
ready for connections:

    sd_notify(true, "READY=1");

or, to be more complete, something akin to:

    status = sd_notify(true, "READY=1");
    if (status < 0)
        warn("cannot notify systemd of startup: %s", strerror(-status));

Then you can be a native systemd daemon and systemd will know exactly when
the KDC is ready to respond to connections, which will resolve various
race conditions when some other system service depends on the KDC for
startup.

-- 
Russ Allbery (eagle at eyrie.org)              <http://www.eyrie.org/~eagle/>