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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