[Engine-devel] [Design for 3.2 RFE] Improving proxy selection algorithm for Power Management operations

[Dan Kenigsberg]

On Sun, Nov 11, 2012 at 01:44:50PM +0200, Itamar Heim wrote:
> On 11/11/2012 01:27 PM, Dan Kenigsberg wrote:
> >On Fri, Nov 09, 2012 at 05:06:05AM -0500, Eli Mesika wrote:
> >>
> >>
> >>----- Original Message -----
> >>>From: "Itamar Heim" <iheim at redhat.com>
> >>>To: "Eli Mesika" <emesika at redhat.com>
> >>>Cc: "engine-devel" <engine-devel at ovirt.org>, "Michael Pasternak" <mpastern at redhat.com>, "Simon Grinberg"
> >>><sgrinber at redhat.com>, "Dan Kenigsberg" <danken at redhat.com>
> >>>Sent: Friday, November 9, 2012 12:02:37 PM
> >>>Subject: Re: [Engine-devel] [Design for 3.2 RFE] Improving proxy selection algorithm for Power Management operations
> >>>
> >>>On 11/09/2012 10:52 AM, Eli Mesika wrote:
> >>>
> >>>>>>
> >>>>>>  > FenceWrapper
> >>>>>>
> >>>>>>i understand danken suggested going this way, rather than than
> >>>>>>another
> >>>>>>instance of vdsm.
> >>>>>>is vdsm only calling these scripts today and all logic is in
> >>>>>>engine,
> >>>>>>or
> >>>>>>does vdsm has any logic in wrapping these scripts (not a blocker
> >>>>>>to
> >>>>>>doing FenceWrapper, just worth extracting that logic from vdsm to
> >>>>>>such a
> >>>>>>script, then using it in both. i hope answer is 'no logic'...)
> >>>>vdsm has some logic that maps between the call passed to it from
> >>>>engine and the actual parameters generated for the script.
> >>>>AFAIK, this logic only "builds" the correct arguments for the
> >>>>command according to the agent type
> >>>>
> >>>
> >>>can we extract it to an external wrapper?
> >>>I'd hate to fix bugs/changes twice for this.
> >>
> >>I'll check it with danken on SUN
> >
> >Saggi has had a nascent attempt to factor the little logic we have out
> >http://gerrit.ovirt.org/#/c/7190/7/vdsm/API.py
> >AFAIR there's nothing there beyond:
> >- log everything but passwords,
> >- build the input stream,
> >- run the script
> >- convert its return code
> >and there's also killing dormant scripts on vdsm exist (which I find not
> >important at all).
> 
> if the wrapping isn't doing anything but calling the scripts, then
> doing it again from java isn't an issue.
> it's only an issue if there is any business logic in the wrapping.

I believe there's no issue. The only so-called-reason for this verb
existing in Vdsm is the pre-historical platform of oVirt-Engine's
predecessor, which did not support[*] running the fence-agent scripts.
That's why I'm advocating to cut the middle man (even though he is I).

[*] "no support" meaning: "possible, but no one's gonna help you if
there's trouble."