Open Stack

Hi, I'd like you to take a look at this patch for potential
DocImpact.
https://review.openstack.org/27160

Log:
commit 77211ab3c070bafe81be75e4acb3c7cd0a8ba98a
Author: Alvaro Lopez Garcia <aloga at ifca.unican.es>
Date:   Thu Apr 18 17:28:27 2013 +0200

    Normalize the weights instead of using raw values.
    
    The weight system is being used by the scheduler and the cells code.
    Currently this system is using the raw values instead of normalizing them.
    This makes difficult to properly use multipliers for establishing the
    relative importance between two wheighers (one big magnitude could
    shade a smaller one).
    
    Changes in this commit:
    
    1) it introduces weight normalization so that we can apply multipliers
    easily. All the weights for an object will be normalized between 0.0 and
    1.0 before being sumed up, so that the final weight for a host will be:
    
        weight = w1_multiplier * norm(w1) + w2_multiplier * norm(w2) + ...
    
    2) RAMWeigher and RamByInstanceTypeWeigher have been modified so as to
    introduce a new "ram_weight_inverse" flag. Before, these weighers stated
    that to change the behaviour to "stacking" instead of "spreading", a
    negative multiplier would do the trick but this is not true when using
    more that one weigher.
    
    3) weights.BaseWeighter has been changed into an ABC so that we enforce
    that all weighers have the expceted methods.
    
    4) Adapt the existing weighers to the above changes.
    
    5) unittests for all of the above
    
    Implements blueprint normalize-scheduler-weights
    DocImpact
    
    Change-Id: I81bf90898d3cb81541f4390596823cc00106eb20

Automatically generated bug (please review):
https://bugs.launchpad.net/bugs/1196980