Re: interesting claims

[Steve Litt <slitt@troubleshooters.com>]

On Wed, 01 May 2019 18:13:53 +0000
"Laurent Bercot" <ska-supervision@skarnet.org> wrote:

> >So Laurent's words from http://skarnet.org/software/s6/ were just
> >part of a very minor family quarrel, not a big deal, and nothing to
> >get worked up over.  
> 
>   This very minor family quarrel is the whole difference between
> having and not having a 100% reliable system, which is the whole
> point of supervision.

The preceding's true for you, but not for everyone. Some
people, like myself, are perfectly happy with a 95% reliable system. I
reboot once every 2 to 4 weeks to get rid of accumulated state, or as a
troubleshooting diagnostic test. I don't think I'm alone. Some people
need 100% reliable, some don't.

My liking of supervision is not 100% reliability, but instead 95%
reliability that is also simple, understandable, and lets me write
daemons that don't have to background themselves. I don't think I'm
alone.

 
>   Yes, obviously sinit and ewontfix init are greatly superior to
> systemd, sysvinit or what have you. 

Which is why I call it a family quarrel. Some in our family have a
strong viewpoint on whether PID1 supervises at least one process, and
some don't. But outside our family, most are happy with systemd, which
of course makes most of us retch.

> That is a low bar to clear. And
> the day we're happy with low bars is the day we start getting
> complacent and writing mediocre software.

I'd call it a not-highest bar, not a low bar. Systemd is a low bar.
> 
>   Also, you are misrepresenting my position - this is not the first
> time, and it's not the first time I'm asking you to do better.
> I've never said that the supervision had to be done by pid 1, actually
> I insist on the exact opposite: the supervisor *does not* have to
> be pid 1. What I am saying, however, is that pid 1 must supervise
> *at least one process*, which is a very different thing.

I'm sorry. Either I didn't know the preceding, or I forgot it. And
supervising one process in PID1 makes a lot more sense than packing an
entire supervisor in PID1.


>   s6-svscan is not a supervisor. It can supervise s6-supervise
> processes, yes - that's a part of being suitable as pid 1 - but it's
> not the same as being able to supervise any daemon, which is much
> harder because "any daemon" is not a known quantity.

I understand now.

>   Supervising a process you control is simple; supervising a process
> you don't know the behaviour of, which is what the job of a
> "supervisor" is, is more complex.

I understand now.

Thanks,

SteveT