Re: hello - hanging services

[Charlie Brady <charlieb-supervision@budge.apana.org.au>]

On Tue, 17 Aug 2010, Jean-Michel Bruenn wrote:

> Hello,
> 
> thanks for your answer. Wouldn't it be a good improvement for runit,
> if it would take care of hanging tasks, also?

You gotta detect them first, which is a non-trivial problem 
(algorithmically impossible in general - 
http://en.wikipedia.org/wiki/Halting_problem).

> There's "run", "finish"
> and the "log" stuff - wouldn't it be possible to add "check" as script,

check script already exists, but not what you are suggesting:

http://manpages.ubuntu.com/manpages/jaunty/man8/sv.8.html

> which is running a command all X seconds and if it gets a response it
> knows "ah okay, the service is still running" and if it gets no
> response "oh, the service seems to have died, let's restart it"?
> 
> Of course, totally optional, up to the user whether to use that or not.
> 
> Difficult to implement?

Yes.

Please check the archives - this has been discussed previously.

> Cheers
> 
> On Tue, 17 Aug 2010
> 13:13:55 -0400 (EDT) Charlie Brady
> <charlieb-supervise@budge.apana.org.au> wrote:
> 
> > 
> > On Tue, 17 Aug 2010, Jean-Michel Bruenn wrote:
> > 
> > > Hey, 
> > > 
> > > i'm curious what happens with hung(hanging?) services (or zombies) is it
> > > possible with runit to detect those and restart the service?
> > 
> > hung/hanging services and zombies are different things. A zombie is a 
> > process which doesn't exist - it's just a process remnant - a status 
> > report which the kernel is hanging onto waiting for someone to ask for it. 
> > A hung/hanging services is a real process, but one which isn't doing what 
> > you want it to do. runit does not detect and restart those. It only 
> > restarts processes which have died.
> 
> 
>