[Pacemaker] [PATCH]Bug 2567 - crm resource migrate should support an optional "role" parameter

[Andrew Beekhof]

On Mon, Apr 4, 2011 at 2:43 PM, Holger Teutsch <holger.teutsch at web.de> wrote:
> On Mon, 2011-04-04 at 11:05 +0200, Andrew Beekhof wrote:
>> On Sat, Mar 19, 2011 at 11:55 AM, Holger Teutsch <holger.teutsch at web.de> wrote:
>> > Hi Dejan,
>> >
>> > On Fri, 2011-03-18 at 14:24 +0100, Dejan Muhamedagic wrote:
>> >> Hi,
>> >>
>> >> On Fri, Mar 18, 2011 at 12:21:40PM +0100, Holger Teutsch wrote:
>> >> > Hi,
>> >> > I would like to submit 2 patches of an initial implementation for
>> >> > discussion.
>> > ..
>> >> > To recall:
>> >> >
>> >> > crm_resource --move resource
>> >> > creates a "standby" rule that moves the resource off the currently
>> >> > active node
>> >> >
>> >> > while
>> >> >
>> >> > crm_resource --move resource --node newnode
>> >> > creates a "prefer" rule that moves the resource to the new node.
>> >> >
>> >> > When dealing with clones and masters the behavior was random as the code
>> >> > only considers the node where the first instance of the clone was
>> >> > started.
>> >> >
>> >> > The new code behaves consistently for the master role of an m/s
>> >> > resource. The options "--master" and "rsc:master" are somewhat redundant
>> >> > as a "slave" move is not supported. Currently it's more an
>> >> > acknowledgement of the user.
>> >> >
>> >> > On the other hand it is desirable (and was requested several times on
>> >> > the ML) to stop a single resource instance of a clone or master on a
>> >> > specific node.
>> >> >
>> >> > Should that be implemented by something like
>> >> >
>> >> > "crm_resource --move-off --resource myresource --node devel2" ?
>> >> >
>> >> > or should
>> >> >
>> >> > crm_resource refuse to work on clones
>> >> >
>> >> > and/or should moving the master role be the default for m/s resources
>> >> > and the "--master" option discarded ?
>> >>
>> >> I think that we also need to consider the case when clone-max is
>> >> less than the number of nodes. If I understood correctly what you
>> >> were saying. So, all of move slave and move master and move clone
>> >> should be possible.
>> >>
>> >
>> > I think the following use cases cover what can be done with such kind of
>> > interface:
>> >
>> > crm_resource --moveoff --resource myresource --node mynode
>> >   -> all resource variants: check whether active on mynode, then create standby constraint
>> >
>> > crm_resource --move --resource myresource
>> >   -> primitive/group: convert to --moveoff --node `current_node`
>> >   -> clone/master: refused
>> >
>> > crm_resource --move --resource myresource --node mynode
>> >  -> primitive/group: create prefer constraint
>> >  -> clone/master: refused
>>
>> Not sure this needs to be refused.
>
> I see the problem that the node where the resource instance should be
> moved off had to be specified as well to get predictable behavior.
>
> Consider a a 2 way clone on a 3 node cluster.
> If the clone is active on A and B what should
>
> crm_resource --move --resource myClone --node C
>
> do ?

I would expect it to create the +inf constraint for C but no
contraint(s) for the current location(s)

> This would require an additional --from-node or similar.
>
>> Other than that the proposal looks sane.
>>
>> My first thought was to make --move behave like --move-off if the
>> resource is a clone or /ms, but since the semantics are the exact
>> opposite, that might introduce introduce more problems than it solves.
>
> That was my perception as well.
>
>>
>> Does the original crm_resource patch implement this?
>
> No, I will submit an updated version later this week.
>
> - holger
>
>
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