[jboss-jira] [JBoss JIRA] (JBRULES-3659) matches operator on variable cause intermittent thread fork and throws exception

[Andreas Ali (JIRA)]

     [ https://issues.jboss.org/browse/JBRULES-3659?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andreas Ali updated JBRULES-3659:
---------------------------------

    Steps to Reproduce: 
The java code that does this multiple insertion and firing is like this:

{code:title=Main.java|borderStyle=solid}
package drools;

import org.drools.KnowledgeBase;
import org.drools.KnowledgeBaseFactory;
import org.drools.builder.KnowledgeBuilder;
import org.drools.builder.KnowledgeBuilderFactory;
import org.drools.builder.ResourceType;
import org.drools.definition.KnowledgePackage;
import org.drools.event.rule.DebugWorkingMemoryEventListener;
import org.drools.io.ResourceFactory;
import org.drools.runtime.StatefulKnowledgeSession;

import java.util.Collection;

public class Main {

    static StatefulKnowledgeSession ksession;

    public static void main(String[] argv) throws Exception {
        initRules();

        // fire once to run the no condition LHS
        ksession.fireAllRules();

        for (int i=0;i < 100; i++) {
        Person person = new Person();
        person.setName("Test");
        ksession.insert(person);
        ksession.fireAllRules();
        }

    }

    private static void initRules() {
        KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();

		// this will parse and compile in one step
		kbuilder.add(ResourceFactory.newClassPathResource("main.drl", Main.class), ResourceType.DRL);

		// Check the builder for errors
		if (kbuilder.hasErrors()) {
			System.out.println(kbuilder.getErrors().toString());
			throw new RuntimeException("Unable to compile \"main.drl\".");
		}

		// get the compiled packages (which are serializable)
		Collection<KnowledgePackage> pkgs = kbuilder
				.getKnowledgePackages();

		// add the packages to a knowledgebase (deploy the knowledge packages).
	    KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
		kbase.addKnowledgePackages(pkgs);

		ksession = kbase.newStatefulKnowledgeSession();

		ksession.addEventListener(new DebugWorkingMemoryEventListener());
    }

}

{code}

The Person is a simple POJO

{code:title=Person.java|borderStyle=solid}
public class Person {

    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}
{code}

The rule file that does the matching is like this:

{code:title=main.drl|borderStyle=solid}
package drools;

dialect "mvel"

declare Stuff
	regexp : String
end

rule "Test Regex"
	salience 100
    when
    then
    	Stuff s = new Stuff("Test")
        System.out.println("Insert reg ex variable");
        insert (s);
end

rule "Test Equality"
	salience 10
    when
    	Stuff( $regexp : regexp )
        Person( name matches $regexp )
        //Person( name matches "Test" )
    then
        System.out.println("Found name");
end

rule "Dump person"
    when
        $p : Person( )
    then
        retract ( $p )
end
{code}

  was:
The java code that does this multiple insertion and firing is like this:

{code:title=Main.java|borderStyle=solid}
package drools;

import org.drools.KnowledgeBase;
import org.drools.KnowledgeBaseFactory;
import org.drools.builder.KnowledgeBuilder;
import org.drools.builder.KnowledgeBuilderFactory;
import org.drools.builder.ResourceType;
import org.drools.definition.KnowledgePackage;
import org.drools.event.rule.DebugWorkingMemoryEventListener;
import org.drools.io.ResourceFactory;
import org.drools.runtime.StatefulKnowledgeSession;

import java.util.Collection;

public class Main {

    static StatefulKnowledgeSession ksession;

    public static void main(String[] argv) throws Exception {
        initRules();

        // fire once to run the no condition LHS
        ksession.fireAllRules();

        for (int i=0;i < 100; i++) {
        Person person = new Person();
        person.setName("Test");
        ksession.insert(person);
        ksession.fireAllRules();
        }

    }

    private static void initRules() {
        KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();

		// this will parse and compile in one step
		kbuilder.add(ResourceFactory.newClassPathResource("main.drl", Main.class), ResourceType.DRL);

		// Check the builder for errors
		if (kbuilder.hasErrors()) {
			System.out.println(kbuilder.getErrors().toString());
			throw new RuntimeException("Unable to compile \"main.drl\".");
		}

		// get the compiled packages (which are serializable)
		Collection<KnowledgePackage> pkgs = kbuilder
				.getKnowledgePackages();

		// add the packages to a knowledgebase (deploy the knowledge packages).
	    KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
		kbase.addKnowledgePackages(pkgs);

		ksession = kbase.newStatefulKnowledgeSession();

		ksession.addEventListener(new DebugWorkingMemoryEventListener());
    }

}

{code}

The Person is a simple POJO

{code:title=main.drl|borderStyle=solid}
public class Person {

    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}
{code}

The rule file that does the matching is like this:

{code:title=Person.java|borderStyle=solid}
package drools;

dialect "mvel"

declare Stuff
	regexp : String
end

rule "Test Regex"
	salience 100
    when
    then
    	Stuff s = new Stuff("Test")
        System.out.println("Insert reg ex variable");
        insert (s);
end

rule "Test Equality"
	salience 10
    when
    	Stuff( $regexp : regexp )
        Person( name matches $regexp )
        //Person( name matches "Test" )
    then
        System.out.println("Found name");
end

rule "Dump person"
    when
        $p : Person( )
    then
        retract ( $p )
end
{code}


    
> matches operator on variable cause intermittent thread fork and throws exception
> --------------------------------------------------------------------------------
>
>                 Key: JBRULES-3659
>                 URL: https://issues.jboss.org/browse/JBRULES-3659
>             Project: Drools
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>    Affects Versions: 5.4.0.Final, 5.5.0.Beta1
>         Environment: Windows 7, Java
>            Reporter: Andreas Ali
>            Assignee: Mark Proctor
>              Labels: matchesconstraint, variable
>
> When an event is inserted and fired multiple times where the matches operator is used using a variable (instead of a constant string), a separate thread can be spawn and cause a null pointer exception.
> {code}
> Exception in thread "Thread-0" java.lang.NullPointerException
> 	at org.drools.rule.constraint.ConditionAnalyzer.analyzeSingleCondition(ConditionAnalyzer.java:113)
> 	at org.drools.rule.constraint.ConditionAnalyzer.analyzeCondition(ConditionAnalyzer.java:99)
> 	at org.drools.rule.constraint.ConditionAnalyzer.analyzeCondition(ConditionAnalyzer.java:70)
> 	at org.drools.rule.constraint.MvelConditionEvaluator.getAnalyzedCondition(MvelConditionEvaluator.java:83)
> 	at org.drools.rule.constraint.MvelConstraint.executeJitting(MvelConstraint.java:269)
> 	at org.drools.rule.constraint.MvelConstraint.access$200(MvelConstraint.java:50)
> 	at org.drools.rule.constraint.MvelConstraint$ConditionJitter.run(MvelConstraint.java:249)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
> 	at java.lang.Thread.run(Unknown Source)
> {code}
> This problem disappear when the regexp is a constant string instead of a variable.  No new thread is spawned when using the constant string.
> The thread spawning was observed using a separate profiler tool.
> The exception usually happens in the middle of the console output.  A search on null pointer exception will get you there.

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