Re: Readiness notification exemplars

["Serge E. Hallyn" <serge@hallyn.com>]

On Fri, Apr 03, 2020 at 07:41:25AM +0000, Jonathan de Boyne Pollard wrote:
> Serge E. Hallyn:
> 
> > If making changes to daemons were going to palatable, [...]
> > 
> 
> Clearly, it *is* palatable, given that a few people have been adding the
> systemd mechanism to their programs for several years, now.   Pierre-Yves

Well both that and the less successfull upstart sigstop had the full force
of popular distros behind them.  Still I hope you're right, and maybe I'll
go ahead and post some patches for a few daemons.

> Ritschard's code and Cameron Norman's code come straight out of actual
> service programs.

> Serge E. Hallyn:
> 
> > you are arguing for parsing stdout for a text message and/or using
> > pidfiles (written to an fd)
> > 
> 
> No, M. Bercot is not.  Quite the opposite, in fact.  The s6 readiness
> mechanism demands *neither* pidfiles *nor* standard output.  It's *any* file
> descriptor (as defined by the service), and *just a linefeed* followed by
> closing the descriptor.
> 
> I'm nodding at almost everything M. Bercot is saying here, by the way.
> 
> * http://jdebp.uk./FGA/unix-daemon-readiness-protocol-problems.html

Yes it sounds like I completely misread the earlier emails, sorry about
that.  Now, looking at http://skarnet.org/software/s6/notifywhenup.html,
I'm probably not reading that quite right, but it seems to tie the
proposal to the 'notifcation-fd' file in the service directory, making
it a bit less general.  s6-log however uses the -d argument to pass the
fd, so I'll go with that.

thanks,
-serge