[bind10-dev] Data source configuration

[Shane Kerr]

Jinmei,

On Wednesday, 2012-05-23 23:35:18 -0700,
JINMEI Tatuya / 神明達哉 <jinmei at isc.org> wrote:
> First, regarding the need for using multiple data sources at the same
> time. Forgetting the special in-memory for now (and see below about
> that), while I think we should allow that, I suspect it's an uncommon
> if not unlikely operation.  I believe in the vast majority case
> there's just one real data source (sqlite3, or mysql or postgres, or
> perhaps some form of plain text).

I think it quite possible that people will want to have data sources
that generate answers. For example, CNNIC may need to do this for
mapping traditional Chinese onto simplified Chinese, and of course
people will want to use geo-location. Some of these generated data
sources will make sense to mix with "standard" data sources and of
course an in-memory data source.

I can quite easily imagine a DNS hosting service wanting to support
geo-location as an added feature. Sure, they could run this on a
different server configured for it, but that may not be very satisfying
for companies with lots of physical locations.
  
> Third, about "in memory data source".  As we all know it's special in
> several points, and its specialty is one of the reasons why this
> configuration is a difficult problem (e.g., we need to find a clean
> way to avoid using in-memory for certain applications).  Now I wonder
> whether we can just consider the in-memory thing a "cache" that comes
> with a specific concrete data source, rather than yet another instance
> of data sources (even if the actual implementation is one of data
> source client derived classes).   Also, I think it probably makes
> sense if a single in-memory cache is specific to one particular data
> source.  In fact, according to the first observation, it wouldn't be
> so different from a single global cache (that can possibly cover
> multiple sources).  Also, this model will eliminate the matching
> consistency issue with or without using a cache.

I kind of like the cache idea, with one question... do we ever foresee
having multiple in-memory data models? I can imagine zones where one
model is more efficient; we discussed the reverse DNS tree already at
the face to face meeting as a good example of this.

So I think it may make sense to consider the in-memory data source as
effectively a fully-loaded cache, we should consider this caching to be
a class of activity rather than a total special case.

--
Shane