BIND 10 #698: ModuleCCSession object may group_unsubscribe in the closed CC session in being deleted (was: ModuleCCSession may operate the closed CC session in being deleted)

[BIND 10 Development]

#698: ModuleCCSession object may group_unsubscribe in the closed CC session in
being deleted
-------------------------------------+-------------------------------------
                 Reporter:           |                Owner:  naokikambe
  naokikambe                         |               Status:  new
                     Type:  defect   |            Milestone:  feature
                 Priority:  major    |  backlog item
                Component:           |           Resolution:
  message-library                    |            Sensitive:  0
                 Keywords:           |  Add Hours to Ticket:  0
Estimated Number of Hours:  3.0      |          Total Hours:  0
                Billable?:  1        |
                Internal?:  0        |
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Comment (by naokikambe):

 In trac547, we can see this verbose massage in boss shutting down.
 {{{
 Exception isc.cc.session.SessionError: SessionError('Session has been
 closed.',) in <bound method ModuleCCSession.__del__ of
 <isc.config.ccsession.ModuleCCSession object at 0x9f926ac>> ignored
 }}}
 But note that this is an independent defect from trac547. This is because
 that the ModuleCCSession object does group_unsubscribe in the closed CC
 session when this object is being deleted. To avoid this, we need to add
 the lines in {{{__del__}}} function that detects whether CC session has
 been closed and returns immediately if it's closed. This is a proposed
 patch.
 {{{
 --- a/src/lib/python/isc/config/ccsession.py
 +++ b/src/lib/python/isc/config/ccsession.py
 @@ -152,6 +152,9 @@ class ModuleCCSession(ConfigData):
          self._remote_module_configs = {}

      def __del__(self):
 +        # If the CC Session obejct has been closed, it returns
 +        # immediately.
 +        if self._session._closed: return
          self._session.group_unsubscribe(self._module_name, "*")
          for module_name in self._remote_module_configs:
              self._session.group_unsubscribe(module_name)
 }}}

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Ticket URL: <https://bind10.isc.org/ticket/698#comment:1>
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