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From Josh Elser <josh.el...@gmail.com>
Subject Re: [DISCUSS] MiniAccumuloCluster goals and approach
Date Wed, 26 Mar 2014 15:38:58 GMT


On 3/26/14, 12:10 AM, Sean Busbey wrote:
> ACCUMULO-2143 has developed a conversation about MiniAccumuloCluster's
> intended use and the way we currently implement the difference between MAC
> for external use and MAC for internal Accumulo testing[1].
>
> In particular, Josh had a few major concerns
>
> -----
>
> It doesn't make sense to me why MiniAccumuloCluster is a concrete class
> which, ultimately still tied to a MiniAccumuloClusterImpl.
> MiniAccumuloCluster *requires* a MiniAccumuloClusterImpl or something that
> extends it. This is what's really chafing me about the separation of
> "accumulo user" and "accumulo developer" methods – you *always* have them
> both. Not to mention, this hierarchy is really obnoxious to create a new
> implementation of AccumuloMiniCluster(Impl) because I have to carry all of
> the cruft of the "original" implementation with me.
>
> Bringing this back around to this ticket, while I still don't agree with
> the reasoning that exposing the FileSystem or ZooKeeper object that
> MiniAccumuloClusterImpl is getting us anything other than the ability to
> say "we didn't change this [arbitrary] API". For "users" who might not care
> what the underlying FileSystem or ZooKeeper connection, it's merely an
> extra two items in their editor's code-completion. For "users" who would
> care to use this information, we now make them jump through extra hoops to
> get it. That just doesn't make any sense to me for something we haven't
> even released.
>
> To be honest, I really want to re-open
> ACCUMULO-2151<https://issues.apache.org/jira/browse/ACCUMULO-2151>,
> make MiniAccumuloCluster an interface, MiniAccumuloClusterImpl an
> implementation of said interface, and create some factory class to make
> instances, ala Connector.tableOperations, Connector.securityOperations,
> etc. Right now there's a class we call an "API" that cannot be generically
> extended for the sake of saying "we have an API".
>
> ----
>
> I wanted to avoid having a drawn out discussion on a jira, where folks my
> not notice it. Especially with things being late in 1.6.0 development and
> the potential this has to impact the API.
>
> Personally, I don't have much of a dog in the fight. There's always some
> arbitrary line for where the public API will be, presuming we want to have
> any kind of balance between providing a stable based for others to build on
> and being able to refactor things. I would like us to hold to our API
> promises[2] and I would rather we not leak implementation details
> unnecessarily.
>
> I suspect the choice to make MiniAccumuloCluster a class rather than an
> interface with a factory was driven by the restrictions we put on API
> changes between major versions and the fact that 1.5 had a class you could
> instantiate via constructors[3].

Ok, that makes the most sense to me - I hadn't previously considered the 
"deprecation" cycle since it previously wasn't held to that standard. I 
mocked up some changes to better match the rest of our "public API" 
objects (class, interfaces, factories). If we want to preserve this API 
compatibility from earlier versions, we *could* name the interfaces 
classes (what would normally be MiniAccumuloCluster and 
MiniAccumuloConfig) to something non-standard to support API 
compatibility (just requiring a re-compilation I think).

I would be behind getting the interfaces how we want them long term 
before categorizing these classes as "public". I'm willing to make sure 
we're all happy with this for 1.6.0.

> It's possible we can address some of the major reusability concerns by
> moving most of the implementation back into MAC, liberally using package
> access for members, and making the internal-use MAC extend the public one.
>
>
> [1]: https://issues.apache.org/jira/browse/ACCUMULO-2143
> [2]: http://accumulo.apache.org/governance/releasing.html
> [3]: https://issues.apache.org/jira/browse/ACCUMULO-2151
>

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