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List:       linux-ha-dev
Subject:    Re: [Linux-ha-dev] "monitor_scripts" parameter for the	VirtualDomain
From:       Florian Haas <florian.haas () linbit ! com>
Date:       2008-12-05 12:58:50
Message-ID: 4939258A.7010103 () linbit ! com
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Lars, Dejan,

On 12/05/2008 12:52 PM, Lars Marowsky-Bree wrote:
> On 2008-12-04T17:20:43, Florian Haas <florian.haas@linbit.com> wrote:
> 
>>> The resource must be fully operational after start (or migrate_from)
>>> have completed.  Monitor must immediately be OK.
>> What?
>>
>> If I'm not mistaken, the purpose of an external monitor_script in
>> conjunction with a virtual domain would be to do something like ping it,
>> try to connect to its TCP port 22, connect to its TCP port 445 (for a
>> virtual Windows box), etc. Any such monitor script only has a chance to
>> succeed when the virtual domain is fully booted. The start operation
>> from the VirtualDomain RA (just like that from the Xen RA) returns
>> immediately after the virtualization management API has determined that
>> the virtual domain has successfully _started_ its boot process, not
>> completed it.
>>
>> What would be your suggestion to determine, from Pacemaker's
>> perspective, that a virtual domain is fully booted?
> 
> It's not pacemaker's job to determine that. The RA must wait and not
> return until this state has been reached.

>> 1. Augment the monitor operation with any external monitor_script and
>> block any start or migrate_from until monitor succeeds? In that case,
>> please educate me as to the purpose of monitor timeouts. Or are you
>> saying one would have to adjust start and migrate_from timeouts accordingly?
> 
> Well, sure. start/migrate_from must cover the full time until the
> resource has reached the requested state. Returning earlier is not
> allowed, or rather, possibly will cause subtle errors somewhere.

> Also consider the UI impact. The GUI would show the resource as "green"
> and no longer in transition; still the admin would get a connection
> refused; not good.
>
> start means "start the resource and return when it is started, or some
> error has occured." It does not mean "trigger the start and return".

See I figured that the RA had done its job when the VMM/hypervisor/etc.
reported that the virtual domain successfully initiated its boot sequence.

My bad; I think I catch the drift now. Updated patch to go into Bugzilla
momentarily.

Cheers,
Florian

-- 
: Florian G. Haas
: LINBIT Information Technologies GmbH
: Vivenotgasse 48, A-1120 Vienna, Austria

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