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From Reinhard Poetz <reinh...@apache.org>
Subject Re: [RT] flow machinery
Date Wed, 26 Oct 2005 17:30:45 GMT
Torsten Curdt wrote:

> 3. Continuation Management
> 
> When it comes down to serialization of flow there are 2 aspects.
> One is flow persistence and the other one is flow replication
> across machines.
> 
> In order support flow persistence we would need the make the
> ContinuationManager save and reload serializable continuations.
> ...which is not big deal. Unfortunately replication is a slightly
> different subject.
> 
> The distributed ContinuationManagers would need to synchronize
> the continuation trees across the network or at least find a way
> to direct to the appropriate server that holds the continuation.
> TBH ...I am not eager to re-invent the wheel here. In fact this
> whole machinery is already in place for sessions. Why not re-use it?
> In fact I don't really see a big point of having web continuations
> without sessions anyway.
> 
> Assuming the continuations are stored inside the session, storing
> and restoring the sessions would take care of the persistence.
> Directing to the server with the right session also assures to
> get to the right cocoon instance running the right ContinuationManager.
> 
> Flow replication itself should then also be solved by session
> replication without any further effort. The only open question
> is the continuation expiry mechanism. It might be good enough to
> just run the expiry on every machine ...I am wondering how that
> might affect the replication though.
> 
> Comments?

In one of my projects I don't use the HttpSession at all but I can use a 
stateful webservice (which is a public interface to a JB***-Cache). Most 
probably this means that I have to write my own ContinuationsManager 
implementation.

I'm saying this as I want to show that there are alternative scenarios how 
clustered applications can be implemenented and that we should consider them 
when (re)-designen the interfaces, though I don't think it will be a big deal.

-- 
Reinhard Pötz           Independent Consultant, Trainer & (IT)-Coach 

{Software Engineering, Open Source, Web Applications, Apache Cocoon}

                                        web(log): http://www.poetz.cc
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