5:26 p.m.
I'm using Drools 5.5 (and guvnor)
Can anyone point me to example where a knowledge agent is used with
persistence. I am trying to understand how the knowledgeagent is used with
a persisted session. Fundamentally when my app starts, I am trying to do
one of two things:
If a persisted session does not exist, start a new one and update it
whenever my knowledgebase (in guvnor) changes
ELSE
If a persisted session already exists (i.e. at a system restart), load the
existing session and continue to monitor it for changes.
I have the persistence working and the monitoring of changes (with a
knowledgeagent) working independently, but not together.
My code:
Environment env = KnowledgeBaseFactory.newEnvironment();
env.set(EnvironmentName.ENTITY_MANAGER_FACTORY,myEMF);
env.set(EnvironmentName.TRANSACTION_MANAGER, myTxManager);
To create/retrieve my ksession I have tried both:
ksession =
JPAKnowledgeService.newStatefulKnowledgeSession(kAgent.getKnowledgeBase(),null,env)
This creates a persisted session, but it is never updated with changes
I also tried:
ksession =
kAgent.getKnowledgeBase().newStatefulKnowledgeSession(null,env);
This updates the ksession with changes, but never persists the session
I figure I can add a KnowledgeAgentEventListener to the agent and then
recreate the ksession by hand (in the knowledgeBaseUpdated method). But I
am hoping there is a cleaner/better way.
Thanks for any ideas.
-J
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5:39 p.m.
Is the knowledge agent configured NOT to create a new knowledgebase
every time it detects an update?
That is, did you create it with the option "newInstance" set to false?
On 09/10/2013 03:26 PM, dunnlow wrote:
I'm using Drools 5.5 (and guvnor)
Can anyone point me to example where a knowledge agent is used with
persistence. I am trying to understand how the knowledgeagent is used with
a persisted session. Fundamentally when my app starts, I am trying to do
one of two things:
If a persisted session does not exist, start a new one and update it
whenever my knowledgebase (in guvnor) changes
ELSE
If a persisted session already exists (i.e. at a system restart), load the
existing session and continue to monitor it for changes.
I have the persistence working and the monitoring of changes (with a
knowledgeagent) working independently, but not together.
My code:
Environment env = KnowledgeBaseFactory.newEnvironment();
env.set(EnvironmentName.ENTITY_MANAGER_FACTORY,myEMF);
env.set(EnvironmentName.TRANSACTION_MANAGER, myTxManager);
To create/retrieve my ksession I have tried both:
ksession =
JPAKnowledgeService.newStatefulKnowledgeSession(kAgent.getKnowledgeBase(),null,env)
This creates a persisted session, but it is never updated with changes
I also tried:
ksession =
kAgent.getKnowledgeBase().newStatefulKnowledgeSession(null,env);
This updates the ksession with changes, but never persists the session
I figure I can add a KnowledgeAgentEventListener to the agent and then
recreate the ksession by hand (in the knowledgeBaseUpdated method). But I
am hoping there is a cleaner/better way.
Thanks for any ideas.
-J
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9:59 a.m.
Thanks David. Short answer is yes, I have it set to false.
I am actually combining Spring and Java Configuration (I am doing this all
in the drools-server). I create my KnowledgeAgent in Spring and then pass
it (with the EntityManagerFactory, TransactionManager, and node) to an
"Initializer" bean that creates the ksession (so I can load an existing
session).
My KnowledgeAgent config is as follows:
<drools:grid-node id="node1"/>
<drools:kbase id="kbase1" node="node1"/>
<drools:kagent id="kagent1" kbase="kbase1"
new-instance="false">
<drools:resources>
<drools:resource type="PKG" basic-authentication="enabled"
source="http://localhost:8080/guvnor/org.drools.guvnor.Guvnor/package/Travel/LATEST"
username="user" password="pass"/>
</drools:resources>
</drools:kagent>
<bean id="txManager".....>
<bean id="jpaEntityManagerFactory....>
<bean id="ksessionInit"
class="com.my.trn.KnowedgeSessionInitializer"
depends-on="node1">
<constructor-arg index="0"<ref
bean="jpaEntityManagerFactory"/></constuctor-arg>
<constructor-arg index="1"<ref
bean="txManager"/></constuctor-arg>
<constructor-arg index="2"<ref
bean="kagent1"/></constuctor-arg>
<constructor-arg index="3"<ref
bean="node1"/></constuctor-arg>
</bean>
<bean id="ksession1" factory-bean="ksessionInit"
factory-method="getKsession"/>
then,
public void initialize(Object anEMF, PlatformTransactionManager aTxManager,
KnowledgeAgent kAgent, GridNode anode) {
Environment env="KnowledgeBaseFactory.newEnvironment();
env.set(EnvironmentName.ENTITY_MANAGER_FACTORY, anEMF)
env.set(EnvironmentName.TRANSACTION_MANAGER, aTxManager);
.
kAgent.addEventListener(new KnowledgeAgentEventListener(){.....for
debugging...}
.
Integer maxSession =
getTheMaxSession(((EntityManagerFactory)anEmf).createEntityManager());
if (maxSession==0) {
*ksession=kAgent.getKnowledgeBase()newStatefulKnowledgeSession(null,env);*
} else {
session=JPAKnowledgeService.loadStatefulKnowledgeSession(maxSession,
kAgent.getKnowledgeBase(),null,env);
{
.
.
anode.set("ksession1",ksession);
.
.
}
Note, when I create the new ksesison as above in bold, the new session is
created in the database, and the kagent sees the changes in Guvnor
(although, interestingly when I build vs when I deploy); however, the
persisted session in the database is not updated.
If I try
ksession=kAgent.getKnowledgeBase().newStatefulKnowledgeSession(null,env) the
new session is NEVER created in the database.
If a session already exists, the loadStatefulKnowledgeSession does read the
existing session, and the kagent triggers on a build in guvnor, but the
session is not updated :(
Thanks again for any insight.
-J
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12:48 a.m.
I did some quick experiments with 5.6.0-SNAPSHOT and a local jUnit test (no
Spring and no Guvnor).
I'm also trusting the logs to detect DB activity, so tak e
dunnlow wrote*
(1)
*
Note, when I create the new ksesison as above in bold, the new
session is
created in the database, and the kagent sees the changes in Guvnor
(although, interestingly when I build vs when I deploy); however, the
persisted session in the database is not updated.
*
(2)
*
If I try
ksession=kAgent.getKnowledgeBase().newStatefulKnowledgeSession(null,env)
the new session is NEVER created in the database.
The JPA persistent session is a wrapper for a normal internal session. It
uses commands to intercept WM actions and update the persisted session in
the DB.
So, if you create the session directly from the KAgent's KB, it will not
even see the JPA layer, so (2) won't work.
(1) with the KAgent's newInstance set to false, will update the in-memory
knowledge base and the internal session. The JPA session, however, won't see
the change, so no DB interaction will happen
until you, say, fire all rules (or invoke any other command-dispatching
method through the JPA session)
dunnlow wrote*
(3)
*
If a session already exists, the loadStatefulKnowledgeSession does
read
the existing session, and the kagent triggers on a build in guvnor, but
the session is not updated :(
When I read the session, I can see a DB update. More updates follow when you
invoke actions on the
newly restored session.
First of all, I'd check the behaviour outside of your container.. what you
are seeing may be due to
some persistence bug that was fixed after 5.5 was released. If not, we'll
have to understand what
happens inside Spring
Best
Davide
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dunnlow