Re: hello - hanging services

[Jean-Michel Bruenn <jean.bruenn@ip-minds.de>]

On Wed, 18 Aug 2010 11:23:41 -0400 (EDT)
Charlie Brady <charlieb-supervision@budge.apana.org.au> wrote:

> There are many complications that you probably haven't thought of. What 
> would runit do if the hangcheck script itself hangs? How might you 
> compromise the existing functionality of runit by adding this feature? How 
> many race conditions do you introduce?

I understand your thoughts about this, and yes i have thought about
this, too. But let's make it clear: This can happen with runit as it
is now, also: a weird written run-script or a broken log-script might
compromise the existing functionality of runit (if it doesnt, adding a
new variant like a hangcheck-script wouldn't do so neither). I mean:
what happens currently if one of the services which you're trying to
start hangs? I havent tried yet, so i guess only the service which
you're trying to start would be compromised - not whole runit. And this
wouldn't be the case with my suggestion neither.

Last but not Least: it's an optional feature, just like the log stuff -
You can use it, you don't need to. If some users feel like using it
they know about the risks, if there are really any (as explained above).

> IMO you don't need to have this functionality in runit, which is already 
> doing it's specified task well. You want something else to act as a 
> service watchdog. You use another tool to do that - for instance, nagios.

Probably you're right, though i don't exactly understand your
argumentation because: Runit is starting crashed processes (this
shouldn't be the job of an Init-System - the job of an init-system is
starting processes, not making sure that they're up and running -
thats the job of a software-watchdog). BUT: runit is doing exactly
this. Runit is taking care that your service is up and running, by
restarting it if its crashing - By argueing that "checking whether a
service is responding (and thus working) is not the job of runit", you
might also argue that "restarting a crashed job is not runit's job".

To point it out again: It's just "optionally" for users who'd like such
a feature, extending the current functionality of restarting a crashed
process - If you, or someone else, feels like "this could hurt my whole
system" you don't need to use it. This doesn't make such a feature
useless or bad.

And back to topic: i didn't wanted to request such a feature, i was
just asking whether it would be difficult to implement/possible.
Whether developers or users implement something like this, is not up to
me :)

P.S: i get your mails twice, purpose? :-)

Cheers

-- 
Jean-Michel Bruenn <jean.bruenn@ip-minds.de>