Re: Multiplexing Document Store

[Robert Munteanu <ro...@apache.org>]

Hi Ian,

On Fri, 2015-10-30 at 15:38 +0000, Ian Boston wrote:
> Hi,
> I am trying to enhance a multiplexing document store written
> initially by
> Robert Munteanu to support multiplexing of content under
> /jcr:system/** in
> particular the version store and the permissions store. I have a
> scheme
> that should theoretically work, encoding the target store in the
> entry name
> of the map key.
> 
> However, it seems that DocumentNodeState (and hence
> DocumentNodeBuilder)
> objects created by a DocumentNodeStore get a reference to that
> DocumentNodeStore, bypassing any multiplexing document node store.
> This is
> all ok if all the calls relate to content in the same
> DocumentNodeStore,
> but as soon as anything performs a call into DocumentNodeStore that
> relates
> to a path not within that DocumentNodeStore the multiplexing breaks
> down.
> Code that reads and writes to /jcr:system/** does this.
> 
> I have tried hacking the code to ensure that the reference to
> DocumentNodeStore is replaced by the MultiplexingDocumentNodeStore,
> however
> when I do that, MultiplexingDocumentNodeStore gets calls that have
> insufficient context to route to the correct DocumentNodeStore. I
> could
> hack some more, but if I do, anything that works is unlikely to be
> acceptable to Oak as a patch.

Well, I can relate, as the DocumentStore multiplexing implementation
does have to be a little creative at times to find out the proper
store.

Could you list (some of) the places where the
MultiplexingDocumentNodeStore does not have enough information to know
where to route the operation? Might be helpful as a starting point.

Thanks,

Robert

Re: Multiplexing Document Store

[Ian Boston <ie...@tfd.co.uk>]

Hi Robert,
On 5 November 2015 at 22:58, Robert Munteanu <ro...@apache.org> wrote:

> Hi Ian,
>
> On Fri, 2015-10-30 at 15:38 +0000, Ian Boston wrote:
> > Hi,
> > I am trying to enhance a multiplexing document store written
> > initially by
> > Robert Munteanu to support multiplexing of content under
> > /jcr:system/** in
> > particular the version store and the permissions store. I have a
> > scheme
> > that should theoretically work, encoding the target store in the
> > entry name
> > of the map key.
> >
> > However, it seems that DocumentNodeState (and hence
> > DocumentNodeBuilder)
> > objects created by a DocumentNodeStore get a reference to that
> > DocumentNodeStore, bypassing any multiplexing document node store.
> > This is
> > all ok if all the calls relate to content in the same
> > DocumentNodeStore,
> > but as soon as anything performs a call into DocumentNodeStore that
> > relates
> > to a path not within that DocumentNodeStore the multiplexing breaks
> > down.
> > Code that reads and writes to /jcr:system/** does this.
> >
> > I have tried hacking the code to ensure that the reference to
> > DocumentNodeStore is replaced by the MultiplexingDocumentNodeStore,
> > however
> > when I do that, MultiplexingDocumentNodeStore gets calls that have
> > insufficient context to route to the correct DocumentNodeStore. I
> > could
> > hack some more, but if I do, anything that works is unlikely to be
> > acceptable to Oak as a patch.
>
> Well, I can relate, as the DocumentStore multiplexing implementation
> does have to be a little creative at times to find out the proper
> store.
>
> Could you list (some of) the places where the
> MultiplexingDocumentNodeStore does not have enough information to know
> where to route the operation? Might be helpful as a starting point.
>

If I look at the DocumentStore API, it doesn't look too bad. Every method
that targets a specific store, contains a key or uses an UpdateOp which
contains a primary key. Assuming the store can always be derived from that
primary key, everything should work. What's less clear is the
implementation specific methods that are used within oak-core. I am
reasonably certain that RDBDocumentStore and MongoDocumentStore make
assumptions and call protected methods.

I say, should work, assuming that every reference to a DocumentStore
implementation can be replaced with a reference to the
MultiplexingDocumentStore, so that all calls go via the Multiplexer and non
go direct to the DocumentStore implementation.

To do it properly will be a big patch to oak-core, and I haven't started to
look at oak-lucene. There isn't a great deal of point in preparing that
patch if the Oak committers don't want this.

Best Regards
Ian


>
> Thanks,
>
> Robert
>