Re: Detecting process death for anycast named process monitoring

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Thu, May 03, 2007 at 06:34:42AM +0930, Glen Turner wrote:
> We don't want to be the parent of the running process, because that
> doesn't add robustness. If the parent process dies, then the service
> dies, and the interface still stays up.

Okay.

> We don't want to poll, because that isn't pretty and the polling
> interval needs to be very short on a big ISP's DNS servers.

If you did have a process which polls for the service, what happens if
that process dies?

> I have tried using the various notify functions against /proc, but
> they don't work for that filesystem. I have tried using notify
> against a UNIX domain socket, but notify doesn't work for
> that either.
> 
> Suggestions, or a patch to support notify for /proc or to push
> process death notifications into DBUS or whatever, are welcome.

What if the dbus system dies?  What if your monitoring process dies?

Surely a simple solution is going to be the best solution?  Given that
you're always going to have another process (which might be killed)
your thought about having a parent process monitor the death of the
child seems to be the simplest.

You could also have that process interact with a watchog, so failures
with that process cause a reboot.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of: