+ desiredLocationScore (Instance.dsrdLocTags t) (Node.locationTags p) +
+ Set.size (Node.locationTags p `Set.intersection` Node.locationTags s) }
+ where desiredLocationScore instTags nodeTags
+ | Set.null instTags = 0 -- there are no desired location tags
+ | Set.null ( instTags `Set.intersection` nodeTags ) = 1
+ | otherwise = 0 -- desired location is satisfied
Are you sure that this is a correct way of saying "0 if the location
requirements are
fullfilled, one otherwise"? To me it seems correct, if there is at most one
desired location for the instance, but what wrong if there are two (like
specifying
a desired geographic location and a desired machine type in an inhomogeneous
cluster). I would have expected something along the lines of
| Set.null ( instTags Set.\\ nodeTags) = 0
| otherwise = 1
Let me explain why I decided to do it this way. I thought that if it
doesn't matter where the instance will be placed either on machine a or
on a machine b, it's possible to select both locations as desired. In
that case if one location desire is satisfied - it's ok and there is no
reason for making cluster score bigger.
On the other hand, if we have such contradictive desired locations, one
of them will be always unsatisfied. Since we care only about metric
changes but not about its absolute value it's ok to add plus one for
each unsatisfied desired location as you suggest.
--
Sincerely, Oleg Ponomarev <[email protected]>
