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

[Holger Teutsch]

On Thu, 2011-04-07 at 08:57 +0200, Andrew Beekhof wrote:
> On Wed, Apr 6, 2011 at 5:48 PM, Holger Teutsch <holger.teutsch at web.de> wrote:
> > On Wed, 2011-04-06 at 15:38 +0200, Dejan Muhamedagic wrote:
> >> On Wed, Apr 06, 2011 at 01:00:36PM +0200, Andrew Beekhof wrote:
> >> > On Tue, Apr 5, 2011 at 12:27 PM, Dejan Muhamedagic <dejanmm at fastmail.fm> wrote:
> >> > > Ah, right, sorry, wanted to ask about the difference between
> >> > > move-off and move. The description looks the same as for move. Is
> >> > > it that in this case it is for clones so crm_resource needs an
> >> > > extra node parameter? You wrote in the doc:
> >> > >
> >> > >        +Migrate a resource (-instance for clones/masters) off the specified node.
> >> > >
> >> > > The '-instance' looks somewhat funny. Why not say "Move/migrate a
> >> > > clone or master/slave instance away from the specified node"?
> >> > >
> >> > > I must say that I still find all this quite confusing, i.e. now
> >> > > we have "move", "unmove", and "move-off", but it's probably just me :)
> >> >
> >> > Not just you.  The problem is that we didn't fully understand all the
> >> > use case permutations at the time.
> >> >
> >> > I think, not withstanding legacy computability, "move" should probably
> >> > be renamed to "move-to" and this new option be called "move-from".
> >> > That seems more obvious and syntactically consistent with the rest of
> >> > the system.
> >>
> >> Yes, move-to and move-from seem more consistent than other
> >> options. The problem is that the old "move" is at times one and
> >> then at times another.
> >>
> >> > In the absence of a host name, each uses the current location for the
> >> > named group/primitive resource and complains for clones.
> >> >
> >> > The biggest question in my mind is what to call "unmove"...
> >> > "move-cleanup" perhaps?
> >>
> >> move-remove? :D
> >> Actually, though the word is a bit awkward, unmove sounds fine
> >> to me.
> >
> > I would vote for "move-cleanup". It's consistent to move-XXX and to my
> > (german) ears "unmove" seems to stand for the previous "move" being
> > undone and the stuff comes back.
> >
> > BTW: Has someone already tried out the code or do you trust me 8-D ?
> 
> I trust no-one - which is why we have regression tests :-)
> 
> >
> > Stay tuned for updated patches...

Now, after an additional discussion round I propose the following:
Please note that for consistency the "--node" argument is optional for "--move-from"

New syntax:
-----------

crm_resource --move-from --resource myresource --node mynode
   -> all resource variants: check whether active on mynode, then create standby constraint

crm_resource --move-from --resource myresource
   -> primitive/group: set --node `current_node`, then create standby constraint
   -> clone/master: refused

crm_resource --move-to --resource myresource --node mynode
  -> all resource variants: create prefer constraint

crm_resource --move-to --resource myresource --master --node mynode
  -> master: check whether active as slave on mynode, then create prefer constraint for master role
  -> others: refused

crm_resource --move-cleanup --resource myresource
  -> zap constraints

As we are already short on meaningful single letter options I vote for long options only.

Backwards Compatibility:
------------------------

crm_resource {-M|--move} --resource myresource
  -> output deprecation warning
  -> treat as crm_resource --move-from --resource myresource

crm_resource {-M|--move} --resource myresource --node mynode
  -> output deprecation warning
  -> treat as crm_resource --move-to --resource myresource --node mynode

crm_resource {-U|--unmove} --resource myresource
  -> output deprecation warning
  -> treat as crm_resource --move-cleanup --resource myresource

For the shell:
Should we go for similar commands or keep "migrate-XXX"


Coming back to Dejan's proposal of "move-remove":

That can be implemented of reexecuting the last move (a remove).
Reimplemeting "unmove" as undo of the last move you have shortcuts for your favorite move operation

move
move-unmove -> back
move-remove -> and forth

Just kidding...
 

> >
> > - holger
> >>