[rules-users] Dynamic updates of stateful sessions
Mattias Avelin
mattias.avelin at netlight.se
Tue Apr 19 03:24:20 EDT 2011
Hi!
Yes, I have already implemented a KnowledgeAgentEventListener acts on KnowledgeBaseUpdatedEvent and ResourceCompilationFailedEvent. I use this to update my knowledgebase reference in my class that wraps the KnowledgeBase and KnowledgeAgent. Below is the code for this class ("DynamicDecisionService"). I suspect that I have missed something vital since I'm actually not getting my knowledgebase to update itself either but I "do it myself" in the listener when I receive a KnowledgeBaseUpdatedEvent.
Here is the code that handles the KnowledgeAgent and KnowledgeBase (I have stripped out some labels and comments since this belongs to the client).
Best regards
Mattias Avelin
package com.x.service;
import java.util.ArrayList;
import org.apache.log4j.Logger;
import org.drools.KnowledgeBase;
import org.drools.KnowledgeBaseConfiguration;
import org.drools.KnowledgeBaseFactory;
import org.drools.agent.KnowledgeAgent;
import org.drools.agent.KnowledgeAgentConfiguration;
import org.drools.agent.KnowledgeAgentFactory;
import org.drools.builder.KnowledgeBuilderError;
import org.drools.builder.KnowledgeBuilderErrors;
import org.drools.conf.EventProcessingOption;
import org.drools.event.knowledgeagent.KnowledgeBaseUpdatedEvent;
import org.drools.event.knowledgeagent.ResourceCompilationFailedEvent;
import org.drools.event.rule.DefaultKnowledgeAgentEventListener;
import org.drools.io.ResourceChangeScannerConfiguration;
import org.drools.io.ResourceFactory;
/**
* {@inheritDoc}
* <p>
* This implementation of DecisionService updates the knowledgebase dynamically
* when the underlying rules (drl-files) are updated. Therefore each call to the
* createSession() method will return a session based on the most resent version
* of the rules (allowing for some lag due to the intervals of the
* resource scanner).
* </p>
* <p>
* For statefull sessions the session needs to be updated "manually" when the
* KnowledgeBase has been updated.
* </P>
* @author Mattias Avelin - mattias.avelin at netlight.se
*/
public class DynamicDecisionService implements DecisionService
{
private static Logger LOG = Logger.getLogger(DynamicDecisionService.class);
// Repository of all the application's knowledge definitions
private KnowledgeBase kBase;
// The agent that monitores the rule files (resources) for changes
private KnowledgeAgent kAgent;
// Decision service type
private DecisionSessionType type;
// When the current knowledgebase was created
private long kbaseLastUpdated;
/**
* Create a DynamicDecisionService using a ChangeSet.
*
* @param changeSet - The ChangeSet referencing the rule-files to use
* for this service. Expects a classpath reference
*
* @throws IllegalArgumentException if changeSet is not a valid ChangeSet.
*/
public DynamicDecisionService(
String changeSet,
DecisionSessionType type)
{
this.kBase = createKnowledgeBase(type);
// the method could reference kBase itself but I thought it
// more more "clear" if I actually supply it in the method invocation
this.kAgent = createKnowledgeAgent(changeSet, this.kBase);
// This should not be neccesary according to all sources I've found
// but without re-assigning the reference it doesn't work!?!?
this.kBase = kAgent.getKnowledgeBase();
this.kbaseLastUpdated = System.currentTimeMillis();
}
/**
* {@inheritDoc}
*/
public DecisionSession createSession ()
{
return new DecisionSession(kBase.newStatefulKnowledgeSession());
}
/**
* {@inheritDoc}
*/
public DecisionSession updateSession (DecisionSession oldSession)
{
// Create a new session from the current KnowledgeBase
DecisionSession newSession =
new DecisionSession(kBase.newStatefulKnowledgeSession());
if(oldSession != null)
{
// "Clean" the old session of all stateless facts before update
oldSession.removeAllStatelessKnowledge();
// Copy all remaining facts to the new session
newSession.uploadKnowledge(new ArrayList(oldSession.getAllFacts()));
}
return newSession;
}
/**
* {@inheritDoc}
*/
public boolean isSessionStale(DecisionSession decisionSession)
{
if(decisionSession.getCreationTime() < this.kbaseLastUpdated)
{
return true;
}
else
{
return false;
}
}
/**
* Create a KnowledgeBuilder from a ChangeSet.
*
* @param changeSet - The ChangeSet
* @return A KnowledgeBuilder
* @throws IllegalArgumentException if changeSet is not a valid ChangeSet.
*/
private KnowledgeAgent createKnowledgeAgent(
String changeSet,
KnowledgeBase kbase)
{
// Configure KnowledgeAgentFactory
configureAgentFactory();
// Create the knowledge agent
KnowledgeAgent agent = KnowledgeAgentFactory.newKnowledgeAgent(
"classificationAgent",
kbase);
agent.applyChangeSet(ResourceFactory.newClassPathResource(changeSet));
// Add actionListener for detecting rule updates
agent.addEventListener(new xKnowledgeAgentEventListener());
// Start the monitoring...
ResourceFactory.getResourceChangeNotifierService().start();
ResourceFactory.getResourceChangeScannerService().start();
return agent;
}
/**
* Configure the agentFactory.
*/
private void configureAgentFactory()
{
// Enable incremental knowledge base build - false means that the
// old knowledge base is "reused" and updated when there are
// updated rules. True means that the old base is discarded and a new
// one is created
KnowledgeAgentConfiguration kagentConf =
KnowledgeAgentFactory.newKnowledgeAgentConfiguration();
kagentConf.setProperty("drools.agent.newInstance", "false");
// Configure the scanning interval - default is 60 sec.
// (Scanning resources for changes...)
ResourceChangeScannerConfiguration sconf =
ResourceFactory.getResourceChangeScannerService().newResourceChangeScannerConfiguration();
sconf.setProperty("drools.resource.scanner.interval", "30");
ResourceFactory.getResourceChangeScannerService().configure(sconf);
}
/**
* Create a KnowledgeBase. For CEP (Drools Fusion) decision service
* use type = STATE_FULL otherwise use STATE_LESS.
*
* @param type - The type KnowledgeBase, state full or state less
*
* @return A KnowledgeBase
*/
private KnowledgeBase createKnowledgeBase(DecisionSessionType type)
{
KnowledgeBase kbase;
if(type.equals(DecisionSessionType.STATE_FULL)){
KnowledgeBaseConfiguration config = KnowledgeBaseFactory.newKnowledgeBaseConfiguration();
config.setOption( EventProcessingOption.STREAM );
kbase = KnowledgeBaseFactory.newKnowledgeBase( config );
}
else
{
kbase = KnowledgeBaseFactory.newKnowledgeBase();
}
return kbase;
}
/**
* Get the ServiceType of this Service.
*
* @return The ServiceType of this service (STATE_FULL or STATE_LESS)
*/
public DecisionSessionType getType ()
{
return type;
}
/**
* When was the KnowledgeBase last updated.
*
* @return The timestamp (ms) for last update of KnowledgeBase
*/
public long getLastUpdated()
{
return this.kbaseLastUpdated;
}
/**
* Custom event listener for acting on events such as rule updates and
* rule loading errors.
*/
private class xKnowledgeAgentEventListener
extends DefaultKnowledgeAgentEventListener
{
/**
* Update the working copy of the KnowledgeBase when detecting
* a updated one.
*
* @param event - The event signalling that the rule base has been updated
*/
@Override
public void knowledgeBaseUpdated (
KnowledgeBaseUpdatedEvent event)
{
LOG.info("Detected updated rules! Rebuilding knowledgeBase!");
long startTime = System.currentTimeMillis();
kBase = kAgent.getKnowledgeBase();
long endTime = System.currentTimeMillis();
// Update the timestamp for when the knowledgeBase was updated
kbaseLastUpdated = endTime;
LOG.info("Rebuilding knowledgebase took " +
(endTime - startTime) + "ms...");
}
/**
* Log errors when problems updating the knowledge base.
*
* @param event - the Event signalling failure to load updated rules
*/
@Override
public void resourceCompilationFailed (
ResourceCompilationFailedEvent event)
{
KnowledgeBuilderErrors errors =
event.getKnowledgeBuilder().getErrors();
if (errors.size() > 0)
{
LOG.error("Errors loading knowledge.");
for (KnowledgeBuilderError error : errors)
{
LOG.error(error);
}
}
}
}
}
________________________________________
From: rules-users-bounces at lists.jboss.org [rules-users-bounces at lists.jboss.org] On Behalf Of Esteban Aliverti [esteban.aliverti at gmail.com]
Sent: Monday, April 18, 2011 19:18
To: Rules Users List
Subject: Re: [rules-users] Dynamic updates of stateful sessions
Maybe the new rules fail to compile. You can add an KnowledgeAgentEventListener to the agent to check for compilation errors.
Could you post some code snippet showing how are you creating the kagent, the kbase, etc.
You can take a look at some tests using newInstence=false here:
https://github.com/droolsjbpm/drools/blob/master/drools-compiler/src/test/java/org/drools/agent/KnowledgeAgentIncrementalChangeSetTest.java
Best Regards,
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Esteban Aliverti
- Developer @ http://www.plugtree.com
- Blog @ http://ilesteban.wordpress.com
On Mon, Apr 18, 2011 at 1:31 PM, Mattias Avelin <mattias.avelin at netlight.se<mailto:mattias.avelin at netlight.se>> wrote:
Thanks for the swift reply!
I have configured my Knowledge Agent to reuse the same KnowledgeBase (set drools.agent.newInstance property to "false" in my KnowledgeAgentConfiguration) as described in the Expert documentation. But my stateful session keeps using the old rules event though I can see from the log output that the Knowledgebase has been updated.
/Mattias
________
From: rules-users-bounces at lists.jboss.org<mailto:rules-users-bounces at lists.jboss.org> [rules-users-bounces at lists.jboss.org<mailto:rules-users-bounces at lists.jboss.org>] On Behalf Of Esteban Aliverti [esteban.aliverti at gmail.com<mailto:esteban.aliverti at gmail.com>]
Sent: Monday, April 18, 2011 16:49
To: Rules Users List
Subject: Re: [rules-users] Dynamic updates of stateful sessions
By default, the Knowledge Agent creates a new kbase when changes in the monitored resources are detected. So the stateful sessions you had are not going to "see" the changes because they belong to a different kbase.
If you want the agent to apply the changes to the current kbase, you need to set drools.agent.newInstance property to "false" in knowledge agent configuration.
You can read about this here: http://ilesteban.wordpress.com/2010/03/25/knowledge-agent-incremental-change-set-processing-and-binary-diff/
If you are defining the kagent using spring, you can use the "newInstence" attribute of <kagent> bean.
Best Regards,
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Esteban Aliverti
- Developer @ http://www.plugtree.com
- Blog @ http://ilesteban.wordpress.com
On Mon, Apr 18, 2011 at 11:41 AM, Mattias Avelin <mattias.avelin at netlight.se<mailto:mattias.avelin at netlight.se><mailto:mattias.avelin at netlight.se<mailto:mattias.avelin at netlight.se>>> wrote:
We have a application in which we have both stateless & stateful sessions
running. We're using the KnowledgeAgent and ChangeSets to automatically
update our knowledge bases when the rules are changed.
This works fine for our stateless sessions for which we are creating a new
session for each request and if the rules have been updated this is
reflected in next session we create.
But for stateful sessions I'm not quite as sure on how to get it working. I
can see in the logs that the KnowledgeBase is re-built when the
KnowledgeAgent detects the updated rule files. But my "long running" session
is does not reflect these changes (which it shouldn't right?). But how do we
apply these changes to the stateful session without loosing all the facts I
accumulated?
The way I've solved it now is to keep a "last updated" timestamp for the
knowledgeBase and a "created" timestamp for the session and then compare
these before using the session. If the knowledgeBase's "update timestamp" is
later that the sessions "creation timestamp" I create a new Session and then
"manually" copy all facts from the former to the latter.
Is this the way you would do this or is there a better way?
Best Regards
Mattias Avelin
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