BIND 10 #2327: Allocation engine v6: expiration

[BIND 10 Development]

#2327: Allocation engine v6: expiration
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            Reporter:  tomek         |                        Owner:
                Type:  defect        |  stephen
            Priority:  medium        |                       Status:
           Component:  dhcp6         |  reviewing
            Keywords:                |                    Milestone:
           Sensitive:  0             |  Sprint-DHCP-20130103
         Sub-Project:  DHCP          |                   Resolution:
Estimated Difficulty:  0             |                 CVSS Scoring:
         Total Hours:  0             |              Defect Severity:  N/A
                                     |  Feature Depending on Ticket:
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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Changes (by tomek):

 * owner:  tomek => stephen


Comment:

 I've added an new files called test_utils.{cc|h}. The idea here is that it
 will contain more methods that can be shared between tests. As there could
 be potentially tens of small utility functions, I think it should be one
 mix-and-match file, rather then lots of small files. They are all linked
 together anyway.

 Added comments as requested. In particular commented on drawback on
 current approach to expiration, i.e. we can't do reference counting for
 subnets. That is not necessarily a bad thing - it is just a tradeoff. We
 work better in the average case, but we will be very slow when totally out
 of available addresses.

 Personally, I think this area will be improved many times throughout the
 lifetime of this software. One idea briefly discussed was to implement
 dynamic switch between allocation policies depending on current conditions
 (e.g. running over 90% allocation? give up on random allocator and switch
 to iterative).

 Fixes pushed. Ok to merge?

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Ticket URL: <https://bind10.isc.org/ticket/2327#comment:7>
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