BIND 10 #191: Implement a initial version of stats

[BIND 10 Development]

#191: Implement a initial version of stats
-----------------------------+----------------------------------------------
      Reporter:  naokikambe  |        Owner:  jinmei              
          Type:  task        |       Status:  reviewing           
      Priority:  major       |    Milestone:  y2 6 month milestone
     Component:  statistics  |   Resolution:                      
      Keywords:              |    Sensitive:  0                   
Estimatedhours:  0.0         |        Hours:  0.25                
      Billable:  0           |   Totalhours:  3.08                
      Internal:  0           |  
-----------------------------+----------------------------------------------
Changes (by jinmei):

  * hours:  0.0 => 0.25
  * totalhours:  3.08 => 3.33


Comment:

 I also have some high level questions about the design of stats.py:

  - I don't see the need for the abstraction using the observer pattern
 because there is only type of listener (=observer).  what's the background
 rationle of this design decision?  Please describe it in more detail in
 the source code.
  - Likewise, I was not sure about the intent of the seeming introduction
 of singleton.  From a very superficial look at the code the intent seems
 to make SessionSubject a singleton class, but at least in the usage of
 stats.py we don't have to bother to have such a tricky technique, because
 there cannot be more than one SessionSubject object in the first place.
 Besides, I suspect this implementation actually doesn't realize what is
 seeminly intended:
 {{{
 class SessionSubject(Subject):
     """
     A concrete subject class which creates CC session object
     """
     __metaclass__ = Singleton
 }}}
   according to a python 2-to-3 guide, this syntax has been depreciated:
 http://diveintopython3.org/porting-code-to-python-3-with-
 2to3.html#metaclass
   Please clarify the intent of the code in more detail.

-- 
Ticket URL: <http://bind10.isc.org/ticket/191#comment:12>
BIND 10 Development <http://bind10.isc.org>
BIND 10 Development