BIND 10 #2401: synchronous communication between DataSrcClientsMgr and DataSrcClientsBuilder

[BIND 10 Development]

#2401: synchronous communication between DataSrcClientsMgr and
DataSrcClientsBuilder
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |                       Status:  new
            Priority:  medium        |                    Milestone:  Next-
           Component:  b10-auth      |  Sprint-Proposed
           Sensitive:  0             |                     Keywords:
         Sub-Project:  DNS           |              Defect Severity:  N/A
Estimated Difficulty:  0             |  Feature Depending on Ticket:
         Total Hours:  0             |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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 I think we need to provide a "synchronous mode" of command exchange
 between the `auth::DataSrcClientsMgr` and `auth::DataSrcClientsBuilder`
 classes.

 Test and benchmark code will need this for deterministic behavior,
 and I guess in some cases the main auth server will need it.  For
 example, in the very initial startup it may rather block than
 prematurely returning REFUSED to all queries.

 One possible approach is to introduce sequence numbers for commands
 and another communication queue between the manager and builder.  When
 the manager wants a specific command to be done in the synchronous
 mode, it sends it to the builder with a valid (non 0 or something)
 sequence number.  If a command has a valid sequence number, the
 builder notifies the manager of its completion via the separate queue
 with that number (and probably some result code).

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Ticket URL: <http://bind10.isc.org/ticket/2401>
BIND 10 Development <http://bind10.isc.org>
BIND 10 Development