BIND 10 #2207: define and implement (datasrc::memory::)ZoneUpdater class

[BIND 10 Development]

#2207: define and implement (datasrc::memory::)ZoneUpdater class
-------------------------------------+-------------------------------------
                   Reporter:         |                 Owner:
  jinmei                             |                Status:  new
                       Type:  task   |             Milestone:  Next-Sprint-
                   Priority:         |  Proposed
  medium                             |            Resolution:
                  Component:  data   |             Sensitive:  0
  source                             |           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      |
-------------------------------------+-------------------------------------
Description changed by jinmei:

Old description:

> A subtask of #2201, depend on #2206.
>
> See the conceptual definition below.
>
> {{{#!cpp
> // Provide interfaces for staged zone loading, hiding the underlying
> // memory segment model.
> class isc::datasrc::memory::ZoneUpdater {
> public:
>     // (Conceptually) load zone(s) content in memory.  This can take
>     // long time.
>     // For the local memory segment version, it creates a new ZoneData
> using
>     // the zone table's local memory segment, and load the zone using
>     // the given load_action.
>     // For the shared memory segment version, this is probably no-op
>     // (the time consuming part should have been done by the
> "b10-memmgr")
>     virtual void load() = 0;
>
>     // Install the new zone image so it can actually be used by the
> caller.
>     // For the local memory segment version, it saves the old version of
>     // ZoneData from the table and inserts the newly created one  in
> load()
>     // to the zone table.
>     // The shared memory version would just internally create
>     // a new MemorySegment object with a given shared segment parameter,
>     // and pass it to the caller via the install_action.
>     virtual void install() = 0;
>
>     // (Conceptually) release any resource used for the older version of
> zone.
>     // This can take long time.
>     // The local memory version destroys the saved (in install()) old
> version
>     // of ZoneData.
>     // The share memory version would probably be no-op.
>     virtual void cleanup() = 0;
> };
> }}}
>
> Aand implement the `ZoneUpdaterLocal` derived class:
>
> {{{#!cpp
> // local memory segment version of ZoneUpdater
> class ZoneUpdaterLocal : public ZoneUpdater {
> public:
>     ZoneUpdaterLocal(ztable_segment, load_action, install_action);
>     ...
> };
> }}}
>
> Finally, add the getZoneUpdater() method to `ZoneTableSegment`
> (see #2206) and implement it for `ZoneTableSegmentLocal`.

New description:

 A subtask of #2201, depend on #2206.

 See the conceptual definition below.

 {{{#!cpp
 // Provide interfaces for staged zone loading, hiding the underlying
 // memory segment model.
 class isc::datasrc::memory::ZoneUpdater {
 public:
     // (Conceptually) load zone(s) content in memory.  This can take
     // long time.
     // For the local memory segment version, it creates a new ZoneData
 using
     // the zone table's local memory segment, and load the zone using
     // the given load_action.
     // For the shared memory segment version, this is probably no-op
     // (the time consuming part should have been done by the "b10-memmgr")
     virtual void load() = 0;

     // Install the new zone image so it can actually be used by the
 caller.
     // For the local memory segment version, it saves the old version of
     // ZoneData from the table and inserts the newly created one  in
 load()
     // to the zone table.
     // The shared memory version would just internally create
     // a new MemorySegment object with a given shared segment parameter,
     // and pass it to the caller via the install_action.
     virtual void install() = 0;

     // (Conceptually) release any resource used for the older version of
 zone.
     // This can take long time.
     // The local memory version destroys the saved (in install()) old
 version
     // of ZoneData.
     // The share memory version would probably be no-op.
     virtual void cleanup() = 0;
 };
 }}}

 And implement the `ZoneUpdaterLocal` derived class:

 {{{#!cpp
 // local memory segment version of ZoneUpdater
 class ZoneUpdaterLocal : public ZoneUpdater {
 public:
     ZoneUpdaterLocal(ztable_segment, load_action, install_action);
     ...
 };
 }}}

 We also need to define `ZoneSegment` class, which is supposed to be
 used as a parameter of the install_action callback.  For the moment we
 don't need to use it, so it can be an empty class:

 {{{#!cpp
 // Eventually this will become an abstract base class
 class ZoneSegment {}
 }}}

 Finally, add the getZoneUpdater() method to `ZoneTableSegment`
 (see #2206) and implement it for `ZoneTableSegmentLocal`.

--

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Ticket URL: <http://bind10.isc.org/ticket/2207#comment:1>
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