Re: (ITS#8707) slapd: Add systemd service notification support

[ryan@nardis.ca]

On Tue, Sep 12, 2017 at 08:24:15PM +0000, hyc@symas.com wrote:
>I don't have documentation for sd_notify() on my machine

https://www.freedesktop.org/software/systemd/man/sd_notify.html

>- what does it return if systemd isn't running at the moment? What does 
>it return if the current program wasn't started by systemd (and thus, 
>the notification is irrelevant)?

0 in both of these cases (assuming there is not an unrelated 
NOTIFY_SOCKET env var). However, it also says:

>In order to support both service managers that implement this scheme 
>and those which do not, it is generally recommended to ignore the 
>return value of this call."

and the current patch doesn't follow that recommendation, since it does 
check the return value. I don't feel strongly either way about that.

>It strikes me that this code should only be invoked if slapd was actually
>started by systemd.

As I understand it, sd_notify() should be a no-op (no error) if 
NOTIFY_SOCKET is not set. I don't think we should check NOTIFY_SOCKET 
ourselves; it's to some extent an implementation detail.