BIND 10 #2205: introduce a "data source configurator" thread in auth

[BIND 10 Development]

#2205: introduce a "data source configurator" thread in auth
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                   Reporter:         |                 Owner:
  jinmei                             |                Status:  new
                       Type:  task   |             Milestone:  Next-Sprint-
                   Priority:         |  Proposed
  medium                             |            Resolution:
                  Component:         |             Sensitive:  0
  b10-auth                           |           Sub-Project:  DNS
                   Keywords:         |  Estimated Difficulty:  0
            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 vorner):

 Hello

 Replying to [comment:4 jinmei]:
 > I'm not sure if I fully understand above.  Can you provide some
 > sample code snippet to illustrate the idea more specifically?

 OK. I'll skip details like condition variables, mutexes, etc. Let's say we
 have
 a `SynchronizedQueue` container that allows to put objects in and take
 them out
 in separate threads, the taking blocks if there's no object.

 {{{#!c++
 class WorkThread {
 private:
         SynchronizedQueue<boost::function<void ()> > queue_;
 public:
         // Called from the "main" thread. Never blocks.
         void asyncWork(boost::function<void ()> work) {
                 queue_.push_back(work);
         }
         // Running "for ever" in the work/background thread.
         void run() {
                 for (;;) {
                         boost::function<void ()> work =
 queue_.pop_front();
                         work();
                 }
         }
 };
 }}}

 Then, if we want to handle configuration update, we do something like
 this:
 {{{#!c++
 // This one runs a long time, should be run in background
 void handleDatasrcConfig(const isc::data::ConstElementPtr& config) {
         ...
 }

 void configHandler(const isc::data::ConstElementPtr& config) {
         ...
         workThread.asyncWork(boost::bind(handleDatasrcConfig,
 config->get("data_sources")));
         ...
 }
 }}}

 I hope it explains the idea.

 > In any case, specific ways to implement it is up to the developer
 > (and the reviewer, and if it's controversial on review we can discuss
 > it project wide).  The approach mentioned in the description is just
 > an example to give a better idea of what should be done, and doesn't
 > have to be adopted literally.

 Indeed. I just wanted to share the idea if the implementor finds it
 usable,
 because it seems to me the technique is elegant, but mostly unknown in the
 procedural world.

-- 
Ticket URL: <http://bind10.isc.org/ticket/2205#comment:5>
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