[rules-users] Dynamic updates of stateful sessions

[Wolfgang Laun]

2011/4/20 Esteban Aliverti <esteban.aliverti at gmail.com>

> @Wolfgang, maybe I need to update the documentation to explicitly inform
> about this behavior :).


Please do.


> The agent doesn't make anything special to sync the sessions with the
> kbase. If you add a rule by hand to an existing kbase, all the session from
> this kbase will automatically detect the changes.
> Now I'm working in a helper class to create and apply change-set in a
> programatic way. So if you don't want kbases to be automatically modified
> when a resource chages, you can use this helper class.
>

There must be a way to avoid sudden changes in a running stateful session by
KAgent "pushing" an updated KBase. Otherwise I don't think you can use
KAgent without risks. Actually, I'd opt for a "pull" behavour" being the
default with stateful session but it may be too late for that.

Cheers
Wolfgang


> Best Regards,
>
> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
>
> Esteban Aliverti
> - Developer @ http://www.plugtree.com
> - Blog @ http://ilesteban.wordpress.com
>
>
> 2011/4/20 Wolfgang Laun <wolfgang.laun at gmail.com>
>
>> 2011/4/20 Esteban Aliverti <esteban.aliverti at gmail.com>
>>
>>> @Wolfgang: if you are using drools.agent.newInstance=true (the default
>>> configuration), then whenever a change-set is applied, either because you
>>> explicitly force the agent to  do so, or because a monitored resource
>>> changes, the kbase inside the agent is thrown away an a new kbase is
>>> created. So you need to get the kbase from the agent and retrieve a fresh
>>> session from it.
>>> You can confirm this behavior in this set of tests:
>>> https://github.com/droolsjbpm/drools/blob/master/drools-compiler/src/test/java/org/drools/agent/KnowledgeAgentIncrementalChangeSetTest.java
>>>
>>> But, if you are using drools.agent.newInstance=false the internal kbase
>>> (and each stateful session you got from it) is refreshed when a change-set
>>> is applied.
>>>
>>>
>> Would you please point me to the doc where it says "and each stateful
>> session ... is refreshed"?
>>
>> If true, this were an extremely risky operation. Consider a stateful
>> session whizzing along and - smack! - rules change right in the middle of a
>> sequence of firings. Shudder.
>>
>> -W
>>
>>
>>
>>
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>
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