BIND 10 #2676: Provide ccsession::rpc_call and replace usual calls with it

[BIND 10 Development]

#2676: Provide ccsession::rpc_call and replace usual calls with it
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            Reporter:  vorner        |                        Owner:
                Type:  enhancement   |  vorner
            Priority:  medium        |                       Status:
           Component:  Inter-module  |  closed
  communication                      |                    Milestone:
            Keywords:                |  Sprint-20130305
           Sensitive:  0             |                   Resolution:
         Sub-Project:  Core          |  complete
Estimated Difficulty:  2.5           |                 CVSS Scoring:
         Total Hours:  16.62         |              Defect Severity:  N/A
                                     |  Feature Depending on Ticket:
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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Comment (by jinmei):

 Replying to [comment:16 vorner]:

 > For the record, I believe the variable was not set in the previous
 version either. That's why I added the TODO about ignoring errors.

 How can you believe that?

 The very original code:

 {{{#!python
     def do_polling(self):
         seq = self.cc_session.group_sendmsg(
             isc.config.ccsession.create_command("show_processes"),
             'Init')
         (answer, env) = self.cc_session.group_recvmsg(False, seq)
         modules = []
         if answer:
             (rcode, value) = isc.config.ccsession.parse_answer(answer)
             if rcode == 0 and type(value) is list:
                 modules = [ v[2] if type(v) is list and len(v) > 2 \
                                 else None for v in value ]
         # start requesting each module to collect statistics data
         sequences = []
 }}}

 So regardless of the return value of group_recvmsg(), modules is set
 to a null list.

 By de4ecfcd4827e8e0002c426e11e5ad36e7e14da3 you changed that with the
 TODO comment:

 {{{#!python
     def do_polling(self):
         try:
             value = self.mccs.rpc_call('show_processes', 'Init')
             if type(value) is list:
                 modules = [ v[2] if type(v) is list and len(v) > 2 \
                                 else None for v in value ]
         except isc.config.RPCError:
             # TODO: Is it OK to just pass? As part of refactoring,
 preserving
             # the original behaviour.
             pass
         sequences = []
 }}}

 So, if group_recvmsg() returns non 0 answer, rpc_call() raises
 `RPCError`, skipping the initialization of `modules`.  Please at least
 refer to the very original code before making such assertion.

 This also indicated it's really bad we didn't have sufficient tests;
 if we had, we wouldn't have to discuss these things.

-- 
Ticket URL: <http://bind10.isc.org/ticket/2676#comment:17>
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