Re: monit unresponsive to status requests?

[Jan-Henrik Haukeland]

On 15. jul. 2005, at 23.53, Randy Bias wrote:


> On Jul 15, 2005, at 6:27 AM, Jan-Henrik Haukeland wrote:
>
>
> > On 15. jul. 2005, at 09.51, Marco Ermini wrote:
> >
> >
> > > >         Actually, this reminds me of another question, that  
> > > > should arguably be
> > > > in a separate e-mail:  Have you considered having monit handle  
> > > > multiple
> > > > PIDs in a file or multiple PID files for a single "service" that  
> > > > has
> > > > multiple processes.  For example, nfsd typically starts up with
> > > > multiple processes.  It would be nice to tell monit:  make sure  
> > > > there
> > > > are always 8 of these running and gave it 8 PIDs to check.  This  
> > > > seems
> > > > like a very useful feature.
> > > This is what OpenView already did... an this is another reason  
> > > because
> > > I can't scale Monit in a bigger environment, it is confined to minor
> > > projects by now.
> >
> > I'm not sure how we should go about solving this problem. If you  
> > have any ideas, please share.
>
> [...]

It's the program responsibility to create the pid-file and write the  
correct pid to this file, monit will not do this! I'm on thin ice  
here but AFAIK few programs, if any, write all it's pids to the same  
pid file? Even so, it would be kind of wrong since it is the parent  
process that is important (and the one monit needs to watch).

I don't see why it's not sufficient for monit to monitor the parent  
process only. Take for instance apache - it fires off a lot of child  
processes (fork-model) but apache only write the parent process to  
the apache pid file, since this is the important controlling process.

Monit already has a feature for monitoring the number of child  
processes. I think it should be enough to say something like this:

 check process foo
    with pidfile "/var/run/foo.pid"
    start program = "/etc/init.d/foo start"
    stop program = "/etc/init.d/foo stop"
    if children < 8 then alert # or restart

I mean, if monit monitored a pid file with several pids, what could  
monit do more than in the above example if one of those processes  
stopped?

--
Jan-Henrik Haukeland
Mobil +47 97141255