[Engine-devel] Bug 1076530 – engine shouldn't kill the vds running the VM with the hosted engine

[Doron Fediuck]

----- Original Message -----
> From: "Yedidyah Bar David" <didi at redhat.com>
> To: "Doron Fediuck" <dfediuck at redhat.com>
> Cc: "Sandro Bonazzola" <sbonazzo at redhat.com>, "Jiri Moskovcak" <jmoskovc at redhat.com>
> Sent: Sunday, March 16, 2014 12:28:27 PM
> Subject: Re: Bug 1076530 – engine shouldn't kill the vds running the VM with the hosted engine
> 
> Might be better to discuss this on bugzilla.
> 
Bugzilla is not a mailing list. Moving to engine-devel.

> ----- Original Message -----
> > From: "Doron Fediuck" <dfediuck at redhat.com>
> > To: "Sandro Bonazzola" <sbonazzo at redhat.com>
> > Cc: "Yedidyah Bar David" <didi at redhat.com>, "Jiri Moskovcak"
> > <jmoskovc at redhat.com>
> > Sent: Sunday, March 16, 2014 12:01:51 PM
> > Subject: Bug 1076530 – engine shouldn't kill the vds running the VM with
> > the hosted engine
> > 
> > https://bugzilla.redhat.com/show_bug.cgi?id=1076530
> > 
> > Sandro,
> > I think this would be solved by a better validation during setup /
> > deployment.
> 
> This can't be done during Validation in the otopi sense of the word.
> At that point the engine does not exist yet and so we can't know what
> versions it supports etc.
> 
Why not?
You have the vdsm supported versions in a file (dsaversion IIRC)
and you should be able to get the relevant engine info before or
after deploying the DB.

> It might be possible (didn't check) to check the versions right before
> trying to add the host to the cluster. This means we do not want to
> abort (as we can do during Validation if something does not pass it).
> What can we do? Perhaps offer a few options:
> 1. Do abort (will do mostly what happens today)
> 2. Let the user try to manually fix, probably by trying to change
> the compatibility version of the cluster, and then try adding the
> host again
> 3. Try to fix ourselves (same) and try adding again
> 4. Best would be to someone upgrade libvirt and reconfigure vdsm.
> Not sure that's easy or even possible at this stage, where VM is
> running and we do not want to loose it.
> 
> Thinking about this again, I am not sure the current behavior is that
> bad. "Fixing" by re-installing with the correct versions is probably
> way simpler than fixing after installation is (mostly) complete.
> 
> > 
> > I'm not keen on adding hosted-engine logic into the engine code.
> 
> Not sure about that. Not that it would help much, because the root
> problem will still have to be solved, but in principle it might be
> a good thing if the engine knows that killing some host will kill itself,
> and so try harder to not do that and just leave it in some zombie,
> requires-manual-action state. This is obviously more important during
> normal operation than during installation.
> --
> Didi
>