On Wed, Jun 15, 2011 at 04:07:27PM +0200, Florian Haas wrote: > On 2011-06-15 15:50, Alan Robertson wrote: > > On 06/14/2011 06:03 AM, Florian Haas wrote: > >> On 2011-06-14 13:08, Dejan Muhamedagic wrote: > >>> Hi Alan, > >>> > >>> On Mon, Jun 13, 2011 at 10:32:02AM -0600, Alan Robertson wrote: > >>>> On 06/13/2011 04:12 AM, Simon Talbot wrote: > >>>>> A couple of observations (I am sure there are more) on the uniqueness > >>>>> flag for OCF script parameters: > >>>>> > >>>>> Would it be wise for the for the index parameter of the SFEX ocf script > >>>>> to have its unique flag set to 1 so that the crm tool (and others) > >>>>> would warn if one inadvertantly tried to create two SFEX resource > >>>>> primitives with the same index? > >>>>> > >>>>> Also, an example of the opposite, the Stonith/IPMI script, has > >>>>> parameters such as interface, username and password with their unique > >>>>> flags set to 1, causing erroneous warnings if you use the same > >>>>> interface, username or password for multiple IPMI stonith primitives, > >>>>> which of course if often the case in large clusters? > >>>>> > >>>> When we designed it, we intended that Unique applies to the complete set > >>>> of parameters - not to individual parameters. It's like a multi-part > >>>> unique key. It takes all 3 to create a unique instance (for the example > >>>> you gave). > >>> That makes sense. > >> Does it really? Then what would be the point of having some params that > >> are unique, and some that are not? Or would the tuple of _all_ > >> parameters marked as unique be considered unique? > >> > > I don't know what you think I said, but A multi-part key to a database > > is a tuple which consists of all marked parameters. You just said what > > I said in a different way. > > > > So we agree. > > Jfyi, I was asking a question, not stating an opinion. Hence the use of > a question mark.
;-) > So then, if the uniqueness should be enforced for a "unique key" that is > comprised of _all_ the parameters marked unique in a parameter set, then > what would be the correct way to express required uniqueness of > _individual_ parameters? > > In other words, if I have foo and bar marked unique, then one resource > with foo=1 and bar=2, and another with foo=1, bar=3 does not violate the > uniqueness constraint. What if I want both foo and bar to be unique in > and of themselves, so any duplicate use of foo=1 should be treated as a > uniqueness violation? With the current "unique=true/false", you cannot express that. Depending on what we chose the meaning to be, parameters marked "unique=true" would be required to either be all _independently_ unique, or be unique as a tuple. If we want to be able to express both, we need a different markup. Of course, we can move the markup out of the parameter description, into an additional markup, that spells them out, like <unique params="foo,bar" /><unique params="bla" />. But using unique=0 as the current non-unique meaning, then unique=<small-integer-or-even-named-label-who-cares>, would name the scope for this uniqueness requirement, where parameters marked with the same such label would form a unique tuple. Enables us to mark multiple tuples, and individual parameters, at the same time. Question is: do we really want or need that. -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com DRBD® and LINBIT® are registered trademarks of LINBIT, Austria. _______________________________________________________ Linux-HA-Dev: Linux-HA-Dev@lists.linux-ha.org http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev Home Page: http://linux-ha.org/
