BIND 10 #2857: memory manager initial exchanges

[BIND 10 Development]

#2857: memory manager initial exchanges
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |                       Status:  new
            Priority:  medium        |                    Milestone:  New
           Component:  shmem         |  Tasks
  manager                            |                   Resolution:
            Keywords:                |                 CVSS Scoring:
           Sensitive:  0             |              Defect Severity:  N/A
         Sub-Project:  DNS           |  Feature Depending on Ticket:
Estimated Difficulty:  5             |  shared memory data source
         Total Hours:  0             |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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Description changed by jinmei:

Old description:

> Subtask of #2830.  Depend on #2856, and msgq membership notification
> framework (#2931).
>
> In this task, complete the memmgr side of
> http://bind10.isc.org/wiki/SharedMemoryIPC#a5.1.InitialStartup
>
> Deal with the case where a reader dies at any timing.

New description:

 (Revised, based on more details of resulting #2854, although the
 details may even change more after review.)

 Subtask of #2830.  Depend on #2856.

 In this task, we focus on the exchange between the main memmgr thread
 and the builder thread introduced in #2855.  Handling users will be
 deferred to #2858 (on a closer look the initial and update exchanges
 don't seem to be so different).

 In this ticket we extend the `Memmgr` class as follows:
 - add a new `__init_segments()` method.  It passes to the builder a
   set of 'load' commands for all initial `SegmentInfo` objects.
   It would look like:
 {{{#!python
     def __init_segments(self, datasrc_info):
         for key, sgmt_info in datasrc_info.segment_info_map.items():
             rrclass, dsrc_name = key
             clist = self._datasrc_clients_mgr.get_client_list(rrclass)
             cmd = ('load', None, dsrc_name, rrclass, clist, sgmt_info)
             sgmt_info.add_event(cmd)
             init_cmd = sgmt_info.start_update()
             assert cmd == ret_cmd and sgmt_info.state == UPDATING
             with self.__cv_commands:
                 self.__command_queue.append(cmd)
                 self.__cv_command.notify()
 }}}
 - update `_setup_module()` so it will register the socket with the
   builder thread with a callback method of `__handle_builder_result`:
 {{{#!python
     def _setup_module(self):
         """Module specific initialization for BIND10Server."""
         # create the builder thread.  register read event with callback
         sockets = socket.socketpair()
         self.__builder = SegmentBuilder(sockets[1])
         self.watch_fileno(sockets[0], self.__handle_builder_result, None,
 None)
         ....
 }}}
 - update `_datasrc_config_handler()` to call `__init_segments()`:
 {{{#!python
             self._datasrc_info_list.append(datasrc_info)
             self.__init_segments(datasrc_info) # #2857 fodder
 }}}
 - add `__handle_builder_result()` method.  for now it only handles the
   case where `SegmentInfo.complete_update()` returns a new command:
 {{{#!python
     def __handle_builder_result(self):
         self.__sock_from_builder.recv(1) # received data don't matter
         updates = []
         with self.__lock_update_queue:
             updates = self.__update_queue
             self.__update_queue = []
         # for each update, do the following:
         event, dsrc_info, rrclass, dsrc_name = updates.pop(0)
         if event == 'load-completed':
             sgmt_info = dsrc_info.segment_info_map((rrclass, dsrc_name))
             cmd = sgmt_info.complete_update()
             if cmd is not None:
                 # send the command to the builder
             elif len(sgmt_info.old_readers) > 0:
                 # notify old readers, deferred to #2858
 }}}

--

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Ticket URL: <http://bind10.isc.org/ticket/2857#comment:2>
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BIND 10 Development