The persistence mechanism for user provided objects is pluggable, based on a given strategy. The reason for this is some people are happy to have their objects serialised with the session state, others have their objects in a DB somewhere and just want a placeholder serialised. This works for process instance variables and also inserted working memory facts.

Mark
On 20/02/2012 15:29, Mike Melton wrote:

That's odd. We have stateful sessions persisted using the techniques shown in the documentation you link to, and rehydrated sessions are fully populated with all facts/events from working memory as expected. We have the same requirement (sessions must survive a server reboot 100% intact) and we have been quite pleased with the results. The only things we have to re-establish upon rehydration are globals and event listeners. We use JPAKnowledgeService.newStatefulKnowledgeSession(..) to establish new persisted sessions and JPAKnowledgeService.loadStatefulKnowledgeSession(..) to rehydrate existing persisted sessions.

I doubt I've been much help to you but perhaps it will help to know that someone has seen persistence work as advertised.

Mike

2012/2/20 Alberto R. Galdo <argaldo@gmail.com>

Hi,

   We are using Drools Expert, Fusion, Flow, etc... to build a complex event processing system and one of our main constraints is to be fault tolerant. As such, we are using an StatefulKnowledgeSession and our system involves processes, sets of rules, events, accumulators, ... . What we need is to be able to reconstruct a KnowledgeSession in a given state and all our changes in the knowledgesession need to be persisted at the very moment a change is detected.

   The documentation is sparse in this point ( http://docs.jboss.org/drools/release/5.4.0.Beta2/drools-expert-docs/html/ch04.html#d0e2702 ) and what we've seen so far is that our rules are persisted but no traces of facts or events ... This would be unaceptable for our product. We need to be able to stop our service at any time and restore the knowledge session at any time as it was at the moment of the previous stop.

   We have previous experience with JBPM 3 using a persistent storage to be fault tolerant and it works like a charm, we can see our processes, process instances, timers, etc...   .

   Can we get a *full* KnowledgeSession persistence service for Drools?


Greets,

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