Re: External health Check Process

[Steve Litt <slitt@troubleshooters.com>]

On Thu, 22 Oct 2020 15:34:37 +0000
"Laurent Bercot" <ska-supervision@skarnet.org> wrote:


>   Hi Oliver,
> 
>   The s6-idiomatic way of doing it would be, as you say, to have a
> separate service that calls an external command (the health checker,
> which is daemon-specific) with a timeout and watches the exit code.
> It is trivial to do in shell, which is why I haven't written any
> particular binary for that.
> 
>   I could add a program that does it for you so you don't have to
> write a 3-line shell script, and a command that creates a s6 service
> directory (or even a s6-rc source definition directory) that watches
> another service using the aforementioned program, it would not be
> hard. However, I am concerned about scope creep, and a common
> criticism I hear from distros is that s6 is "too big" - which is
> unfair considering that integrated init systems providing the same
> level of functionality are 5x-10x bigger, but is really a way of
> saying that there are a lot of exposed binaries with miscellaneous
> functionality and it's difficult to wrap one's head around it. 

Laurent, I agree with you. My main attraction to daemontools, runit and
s6 is they're simple and understandable. There's almost nothing I can't
do with them if I get creative with shellscripts. I understand you
insistence on PID1 supervising the real supervisor: That's worth the
added complexity. I understand your desire to order process
instantiation at boot and to intermix run-once and long-run processes,
think that's worth the added complexity, and in fact this is one of the
few things I missed in daemontools and runit. 

But most of the other suggestions that in my opinion are just answers
to systemd weenie's "but s6 doesn't have _____" arguments, and don't
add nearly enough functionality or convenience for the complexity, or
just plain size added to the user manual, to justify.

The OP already stated there's a way to do it currently. Why complexify
s6 to do something already doable?

SteveT

Steve Litt 
Autumn 2020 featured book: Thriving in Tough Times
http://www.troubleshooters.com/thrive