Effect of KnowledgeAgent reload on currently running rules

Monday, 16 May 2011

If I use the KnowledgeAgent with the 'drools.agent.newInstance' property set to
'false' to automatically reload my KnowledgeBase when resources in the changeset
are updated, what happens to any existing sessions when the agent detects changes and
reloads the KnowledgeBase?  Do they continue to use the old rules or are they somehow
reloaded in midstream?  What adverse effects might I see?

I ask because I'm trying to rework some existing classes that were written to
facilitate the loading and caching of KnowledgeBases created in different ways - e.g.
loading decision tables, loading .drl and .rf files in the traditional manner, loading
.drl and .rf files using an agent.  I'd like to be able to grab a KnowledgeBase from
the cache regardless of how it was created, create a session from it, and fire all of the
rules, but I'm concerned about cached KnowledgeBases created by KnowledgeAgents.  If I
set the newInstance property to 'true', my cached KnowledgeBase will never see the
updates.  If I set it to 'false', my cached KnowledgeBase should see the changes,
but I'm concerned about the behavior in any currently running sessions.

FYI - the classes were originally written using the Drools 4.07 RulesAgent for caching
RuleBases that needed to be automatically reloaded.  It seems to be working as expected. 
I'm trying to update those classes to use Drools 5.1 classes instead.

Thanks,
Jamie

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