BIND 10 #1451: Create DDNS process module

[BIND 10 Development]

#1451: Create DDNS process module
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                   Reporter:  jelte  |                 Owner:  jinmei
                       Type:  task   |                Status:  reviewing
                   Priority:  major  |             Milestone:
                  Component:  DDNS   |  Sprint-20111220
                   Keywords:         |            Resolution:
            Defect Severity:  N/A    |             Sensitive:  0
Feature Depending on Ticket:  DDNS   |           Sub-Project:  DNS
        Add Hours to Ticket:  0      |  Estimated Difficulty:  6
                  Internal?:  0      |           Total Hours:  9
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Comment (by jinmei):

 It looks almost okay.  I have two last comments.

 - I'm afraid it could be dangerous to do all shutdown jobs in the
   middle of a signal handler.  For example, check_command() could
   still be called after shutdown(), but the latter may destruct some
   fundamental attribute of the class at that point.  In general, I
   think it's safer to minimize the things within a signal handler
   (e.g., just setting a flag) and do other complicated jobs in the
   usual control flow.  I have a proposed patch to implement this idea.
   (dddns.diff, attached)

 - TestMain repeats the same pattern and I think it's better to combine
   them in a separate helper method.  See attached diff
   (exception.diff)

 If you are fine with these patched, please just apply them and merge.
 If you simply don't agree, I'm okay with it for now; please feel free
 to merge the current code.  If you don't agree right now but want to
 discuss it more, please continue.

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Ticket URL: <http://bind10.isc.org/ticket/1451#comment:13>
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