Re: [xmlblaster] distributed cluster protocol

[Michele Laghi <laghi at swissinfo.org>]

Hi Michael,
I believe there are three possible solutions:

a) AccessMimePlugin
b) DispatchPlugin
c) I_MessageSecurityInterceptor

for a description of the plugins please have a look at:

http://www.xmlBlaster.org/MessageFlowPubSubOverview.html

Solution a) is probably the cleanest and better performing. It would 
imply some modifications to the interface itself (I_AccessFilter) from

boolean match(SessionInfo, SessionInfo, MsgUnit, Query) to
MsgUnit match(SessionInfo, SessionInfo, MsgUnit, Query)

Here the return value would be

- the message as you want to give it back to the subscriber,
- null if nothing has to be updated or
- the same reference as MsgUnit if it has to be sent without modification.

This solution would also need some (relatively simple) changes to the core.

Solution b) can be implemented without any modification but its 
implementation could be a little complex since the only example 
available is quite specific and not that simple (see the dispatch plugin).

Solution c) can be implemented right the way and is easy to implement. 
Just make an own implementation of the I_MessageSecurityInterceptor (and 
implement the exportMessage method). This is probably the easiest and 
fastest way to do it (probably just some hours) but it would be kind of 
a hack since you use the security plugin for purposes which are not 
security-related.

I said alternative a) is better performing because it modifies the 
message before putting it into the callback queue (b and c would do it 
after the queue). Since the dispatcher framework would put the message 
into the queue again in case of delivery failure, then for b) and c) you 
would modify the content before each trial while a) would do it only once.

Please let us know if you opted for solution a) since we would need to 
prepare the core for the changes.

Michele




Michael Atighetchi wrote:
> Michele, 
>
> is it possible to write a plugin for changing the behavior of a
> xmlblaster server after it has matched publications with subscriptions?
>
> I'm in need for this, as I'd like to only send a selective part of
> the initially published information to the subscribers, and hence
> would like to do post-matching filtering (would be a nice complement
> to the PublishFilter plugin, which does pre-matching filtering).
>
> If it's not high on anyones priority list, I might consider
> implementing this myself and integrating it into the latest cvs
> tree. Any opinions on the prefered design ? 
>
> Michael