KnowledgeAgent and Guvnor restart
by Gerret Hansper
Hello,
I have got an issue with the KnowledgeAgent that seems not to survive a Guvnor
restart. The scenario is as follows:
* We use Drools 5.0
* On our application server we create a KnowledgeAgent
applying a ChangeSet that points to a package binary on a separate Guvnor server
like so:
SystemEventListenerFactory.setSystemEventListener(new
SystemEventLogger());
ResourceFactory.getResourceChangeNotifierService().start();
ResourceFactory.getResourceChangeScannerService().start();
KnowledgeAgent agent =
KnowledgeAgentFactory.newKnowledgeAgent(workflowName);
agent.applyChangeSet(changeSet);
* Creating the kbase, registering globals and running sessions works fine.
* We shut down Guvnor (or the connection goes down, this was how we spotted the
problem) and restart it after a minute
* We then try to run sessions from the
same agent as above via
kagent.getKnowledgeBase().newStatefulKnowledgeSession();
which returns a ksession, but then setting a global we get
java.lang.RuntimeException: Unexpected global [log]
at
org.drools.common.AbstractWorkingMemory.setGlobal(AbstractWorkingMemory.java:5
50)
at
org.drools.impl.StatefulKnowledgeSessionImpl.setGlobal(StatefulKnowledgeSessio
nImpl.java:284)
>From the debugger I can see that indeed the ruleBase's globals map is empty. The
SystemEventLogger indicates that the KnowledgeAgent unsubscribes from its
resource when Guvnor is down and rebuilds its kbase. Also, it stops scanning the
resource and does not find it once Guvnor is up again. (See log snippet below).
Wouldn't it be better in these cases to keep the resource as is in memory and
try to rescan? I figure that as long as the resource is specified in the
changeSet it should be considered part of the kbase and not be removed if it
cannot be found.
For the time being, does anyone have a suggestion how to avoid these problems?
We could catch the RuntimeException and recreate the KnowledgeAgent, but perhaps
there is a better way?
Thanks, Gerret
-- SystemEventLog --
# Guvnor is up here
07:58:01,881 ResourceChangeScanner attempt to scan 1 resources
07:58:02,209 ResourceChangeScanner thread is waiting for 60
07:58:15,067 ResourceChangeScanner attempt to scan 1 resources
# Guvnor goes down here
07:58:16,738 ResourceChangeScanner removed resource=[UrlResource
path='http://localhost:7080/drools-
guvnor/org.drools.guvnor.Guvnor/package/com.foo.bar/LATEST']
07:58:16,738 ResourceChangeNotification received ChangeSet notification
07:58:16,738 ResourceChangeScanner thread is waiting for 60
07:58:16,738 ResourceChangeNotification processing ChangeSet
07:58:16,738 ResourceChangeNotification ChangeSet removed resource=[UrlResource
path='http://localhost:7080/drools-
guvnor/org.drools.guvnor.Guvnor/package/com.foo.bar/LATEST'] for
listener=org.drools.agent.impl.KnowledgeAgentImpl@1053d6d
07:58:16,738 ResourceChangeNotification ChangeSet removed resource=[UrlResource
path='http://localhost:7080/drools-
guvnor/org.drools.guvnor.Guvnor/package/com.foo.bar/LATEST'] for
listener=org.drools.agent.impl.KnowledgeAgentImpl@b71c17
07:58:16,738 KnowledgeAgent received ChangeSet changed notification
07:58:16,738 KnowledgeAgent received ChangeSet changed notification
07:58:16,738 KnowledgAgent applying ChangeSet
07:58:16,738 ResourceChangeNotification thread is waiting for queue update
07:58:16,738 KnowledgAgent applying ChangeSet
07:58:16,738 KnowledgeAgent unsubscribing from resource=[UrlResource
path='http://localhost:7080/drools-
guvnor/org.drools.guvnor.Guvnor/package/com.foo.bar/LATEST']
07:58:16,738 ResourceChangeNotification unsubscribing
listener=org.drools.agent.impl.KnowledgeAgentImpl@1053d6d to
resource=[UrlResource path='http://localhost:7080/drools-
guvnor/org.drools.guvnor.Guvnor/package/com.foo.bar/LATEST']
07:58:16,738 KnowledgeAgent rebuilding KnowledgeBase using ChangeSet
07:58:16,738 KnowledgeAgent unsubscribing from resource=[UrlResource
path='http://localhost:7080/drools-
guvnor/org.drools.guvnor.Guvnor/package/com.foo.bar/LATEST']
07:58:16,738 ResourceChangeNotification unsubscribing
listener=org.drools.agent.impl.KnowledgeAgentImpl@b71c17 to
resource=[UrlResource path='http://localhost:7080/drools-
guvnor/org.drools.guvnor.Guvnor/package/com.foo.bar/LATEST']
07:58:16,738
KnowledgeAgent rebuilding KnowledgeBase using ChangeSet
07:58:16,738 KnowledgeAgent new KnowledgeBase now built and in use
07:58:16,738 KnowledgeAgent new KnowledgeBase now built and in use
07:59:02,202 ResourceChangeScanner attempt to scan 0 resources
07:59:02,202 ResourceChangeScanner thread is waiting for 60
# Guvnor back up here
07:59:16,731 ResourceChangeScanner attempt to scan 0 resources
07:59:16,731 ResourceChangeScanner thread is waiting for 60
--
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15 years, 2 months
StatefulKnowledgeSession Vs StatefulSession
by DeepakA
I used a KnowledgeBuilder ro read the resources (DSL & DSLR files)
Then created a KnowledgeBase and created a StatefulKnowledgeSession out of
the KnowledgeBase.
The StatefulKnowledgeSession was used to start the process and fire all
rules.
Then I realized I was not able to access the RuleBase from
StatefulKnowledgeSession.
So, now I create a RuleBase, then a PackageBuilder, add the resources to the
packageBuilder, then add the
package to the RuleBase and create a StatefulSession out of the RuleBase.
This statefulsession is used to start the process and fire all rules.
Can someone explain to me whats the difference in the above 2 methods of
firing the rules.
Whats the difference between StatefulKnowledgeSession & StatefulSession.
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15 years, 2 months
[Urgent] Error in ontext assist in DSLR Editor
by hamza bakkali
Hi All,
I have been using drools 4 for couple of months now and I am starting to get
the hang of it. We recently decided to move to Dools 5 with Eclipse 3.4.2
(Ganymede).
We unfortunately hit a major 'show stopper' (for us). In the DSLR editor:
Context Assist + space + enter removes/replaces the whole line, not only the
place holder.
In other words:
DSL:
[*][]Log : {msg}=System.out.println("{msg}");
[*][]id1="some id label"
DSLR:
rule "MyRule"
when
then
end
If I Press L , control space --> the line Log:{msg} appears in the context
menu. Hit enter I get
Log :{msg}
Now, If want to replace msg by id1. I position the cursor in the {msg}, hit
ctrl space, id1 shows in the list. I hit enter the whole line disappear, and
I am left with
id1
instead of
Log : id1
Is this a setting somewhere in eclipse itself?? I doubt it.
The same thing use to work as expected in Drools 4.
thanks.
15 years, 3 months
Drools planner & Scala
by Adam Warski
Hello,
I'm using Planner in a Scala program and it almost works without problems; the only one is in implementing the Solution interface, as it uses raw (erased) version of Score, which is normally generic (Score<S extends Score>). Scala generally doesn't like raw types and in most cases it's impossible to extend/implement interfaces which use them. A work-around is to introduce an "adapter" in Java, which you can later extend in Scala:
public abstract class ScalaSolution implements Solution {
public Score getScore() { return getScoreScala(); }
public abstract Score<?> getScoreScala();
public void setScore(Score score) { setScoreScala(score); }
public abstract void setScoreScala(Score<?> score);
}
and then in Scala:
class Schedule(...) extends ScalaSolution {
var score: Score[_] = _
def setScoreScala(score: Score[_]) = { this.score = score }
def getScoreScala = score
...
}
So the fix is to replace the raw Score type with Score<?>. Maybe it would be possible to apply that in the code? I tried it locally and it compiles without problems.
And a side question: do you have any plans on implementing multithreading in planner? So that several moves could be explored concurrently? I saw there's an open Jira issue for some time, but it didn't have any timeframe information.
--
Adam Warski
http://www.warski.org
http://www.softwaremill.eu
15 years, 3 months
How to specify relative URL in chagenset.xml file
by Pardeep Ruhil
Hi,
I am getting File Not Found Exception when I try to give relative path of the file.
<resource source='file:../HelloWorld.drl' type='DRL' />
But when I give the complete path, It picks the changeset.xml file.
<resource source='file:C:/Tomcat/webapps/DroolsCheck/HelloWorld.drl' type='DRL' />
Please tell me the syntax for using the relative path for my workflow or rule files.
Thanks & Regards
Pradeep Ruhil
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15 years, 3 months
taskService restart problem (urgent response needed)
by KiranP
i m having 2-3 tasks in my flow the flow works fine in the normal conditions
the tasks are handled by the MinaTaskServer and MinaTaskClient but the
problem is that it uses the command and the call back mechanism using the
map of tasks request (if i m not wrong) hence when the taskservice restarts
all the callback refrence is lost and completing any task wont updated to
the MinaTaskServer (even if the task is available)
can any one hint me who i can achieve trans-restart task completion.....
till today none of my posts got a reply..............i think u r all
busy............if some one gets time plz help....
bcoz now it has become a grave matter.........it urgent...
thanks
-----
Keep Working >>:working:
KiranP
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15 years, 3 months
Trying to get Eclipse Java code to call Guvnor
by John Peterson
I'm using the example code from the Red Hat Magazine -
http://magazine.redhat.com/2008/08/12/jboss-drools-how-to-tuning-guvnor-
part-1/ - to try to get the sample code to work, but I keep getting the
following error:
Exception in thread "main" java.lang.NullPointerException
at java.util.Properties$LineReader.readLine(Unknown Source)
at java.util.Properties.load0(Unknown Source)
at java.util.Properties.load(Unknown Source)
at
org.drools.agent.RuleAgent.loadFromProperties(RuleAgent.java:299)
at org.drools.agent.RuleAgent.newRuleAgent(RuleAgent.java:256)
at test.GuvnorTest.main(GuvnorTest.java:15)
It appears to be unable to find my 'Guvnor.properties' file, but I have
it in the classpath (I actually have it in several different places on
my C: drive as I tried to figure out why it couldn't find it). Does
anyone have any thoughts on what's wrong here?
I'd appreciate any guidance. It seems like this should be a simple
answer but I haven't been able to figure it out.
15 years, 5 months
About for and inheritance
by Chris Woodrow
Hi,
I recently find out a few issues using for, and I wanted to share it with
you. I made a simple exemple to illustrate my purpose.
My classes are (I did not represent accessors & constructors):
public class Cheese {
protected String name;
}
public class FrenchCheese extends Cheese{
private String smell;
}
public class Person {
private Cheese likes;
}
Here is my rule set :
package rules
rule "likes cheese"
when
$person : Person ()
Cheese( ) from $person.getLikes()
then
System.out.println("likes cheese");
end
rule "likes french cheese"
when
$person : Person ()
FrenchCheese( ) from $person.getLikes()
then
System.out.println("likes french cheese");
end
First test :
Cheese cheese = new FrenchCheese("good", "camembert");
Person person = new Person();
person.setLikes(cheese);
Output :
likes french cheese
likes cheese
Wich is expected...
Second test :
Cheese cheese = new Cheese();
Person person = new Person();
person.setLikes(cheese);
Output :
likes french cheese
likes cheese
That's the first strange thing. As far as I am concerned, rule "likes french
cheese" should not match (since a Cheese is not a FrenchCheese).
I made a change to the second rule :
rule "likes french cheese"
when
$person : Person ()
FrenchCheese( smell == "good" ) from $person.getLikes()
then
System.out.println("likes french cheese");
end
Third test :
Cheese cheese = new Cheese();
Person person = new Person();
person.setLikes(cheese);
output :
It throwed an exception : Exception in thread "main"
java.lang.ClassCastException: rules.Cheese
I am not saying the ClassCastException is not to expect in such a case but I
think I would simply expect it not to match (as far as a Cheese is not a
FrenchCheese).
Chris
15 years, 5 months
