BIND 10 #2211: update the data source reconfigure command so it uses thread

[BIND 10 Development]

#2211: update the data source reconfigure command so it uses thread
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                   Reporter:         |                 Owner:  jinmei
  jinmei                             |                Status:  accepted
                       Type:  task   |             Milestone:
                   Priority:         |  Sprint-20121023
  medium                             |            Resolution:
                  Component:         |             Sensitive:  0
  b10-auth                           |           Sub-Project:  DNS
                   Keywords:         |  Estimated Difficulty:  6
            Defect Severity:  N/A    |           Total Hours:  0
Feature Depending on Ticket:         |
  background zone loading            |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Comment (by jinmei):

 trac2211 is ready for review.  Now at least full data source
 reconfigure runs in the background:-)

 It depends on #2210, which is now under review, but #2210 seems to be
 mostly ready for merge so it should be safe to start reviewing this
 branch.

 The effective branch point is eb90dff (inclusive); I've incorporated a
 snapshot of trac2210 before that, which should be ignored for the
 review.

 The real new code is small, up to around 0e70ad3.  Most of the other
 changes are refactoring: updating exiting auth server's code so it
 uses the new framework, adjusting test setup, cleanup deprecated
 stuff.  I believe existing test semantics is (mostly if not all)
 preserved, but some are moved to datasrc_clients_mgr_unittest and the
 change may seem bigger due to that.

 I also fixed the issue of #2363 at commit 6cf9494.  It's actually a
 small fix, and this branch needs to update the same code, it makes
 more sense to do it here at once.  I've confirmed the fix manually and
 am confident about the fix, but once issues of #2361 are resolved
 I'll also confirm it with the lettuce test.

 I've not all of the additional things hinted in the tickets as the
 branch was getting bigger: I've skipped updating `ModuleCCSession`
 class, and kept the data source config handler still in main.cc.

 Since this is a user visible change, I think it deserves a separate
 changelog entry.  This is the proposed one:
 {{{
 495.?   [func]          team
         b10-auth now handles reconfiguration of data sources in
         background using a separate thread.  This means even if the new
         configuration includes a large amount of data to be loaded into
         memory (very large zones and/or a very large number of zones),
         the reconfiguration doesn't block query handling.
         (Multiple Trac tickets up to #2211)
 }}}

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Ticket URL: <http://bind10.isc.org/ticket/2211#comment:9>
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