[incubator-kie-issues#1753] Load SessionConfiguration at startup in project templates; remove outdated comment in ChainedProperties

[martinweiler]

Closes apache/incubator-kie-issues#1753

[yesamer]

@martinweiler Thank you for your PR, can you please share a brief description of the reason those changes resolve the issue? I'm still not familiar with this codegen area. Thanks :)

[martinweiler]

Hi @yesamer - thanks for looking into this. Let's take a look at the stacktrace posted in apache/incubator-kie-issues#1753, from the bottom up:

"kogito-event-executor-12" #68 daemon prio=5 os_prio=0 cpu=4286.47ms elapsed=215.32s tid=0x00007f2f3d989670 nid=0x6a waiting for monitor entry [0x00007f2f3c7b6000]
java.lang.Thread.State: BLOCKED (on object monitor)
at java.util.zip.ZipFile.getEntry(java.base@17.0.13/ZipFile.java:337)
- locked <0x00000007408c6270> (a sun.net.www.protocol.jar.URLJarFile)
at java.util.jar.JarFile.getEntry(java.base@17.0.13/JarFile.java:513)
at sun.net.www.protocol.jar.URLJarFile.getEntry(java.base@17.0.13/URLJarFile.java:131)
at sun.net.www.protocol.jar.JarURLConnection.connect(java.base@17.0.13/JarURLConnection.java:135)
at sun.net.www.protocol.jar.JarURLConnection.getInputStream(java.base@17.0.13/JarURLConnection.java:175)
at java.net.URL.openStream(java.base@17.0.13/URL.java:1161)
at org.kie.internal.utils.ChainedProperties.read(ChainedProperties.java:229)
        at org.kie.internal.utils.ChainedProperties.getChainedProperties(ChainedProperties.java:74)
        at org.kie.internal.utils.ChainedProperties.getChainedProperties(ChainedProperties.java:70)
        at org.drools.core.impl.RuleBaseFactory.newKnowledgeSessionConfiguration(RuleBaseFactory.java:155)
        at org.drools.project.model.ProjectRuntime.getConfForSession(ProjectRuntime.java:83)
        at org.drools.project.model.ProjectRuntime.newKieSession(ProjectRuntime.java:67)
        at com.test.SampleProcess.lambda$process$136(DataProcess.java:2337)
        at com.test.SampleProcess$$Lambda$1018/0x0000000800706cc0.get(Unknown Source)
        at org.jbpm.workflow.instance.rule.AbstractRuleTypeEngine.getKieRuntime(AbstractRuleTypeEngine.java:35)
        at org.jbpm.bpmn2.rule.RuleFlowGroupRuleTypeEngineImpl.evaluate(RuleFlowGroupRuleTypeEngineImpl.java:39)

• RuleFlowGroupRuleTypeEngineImpl is the integration code that calls Drools from the BPMN process, on each BusinessRuleTask handler node
• It obains a KieRuntime at the beginning of the evaluate method
• The next lines in the stack are from the code generated classes, including the org.drools.project.model.ProjectRuntime class, which is generated based on the template that's being modified in this PR
• The ProjectRuntime.newKieSession method invocation results in the getConfForSession method being called
• In this method, we are seeing the contention under load, due to the ChainedProperties trying to read the same file in multiple threads
• The proposed fix moves the reading of the creation of the SessionConfiguration to the application startup, instead of having it recreated on each bpmn -> drools invocation
• In addition, it removes the comment regarding a cache in ChainedProperties, as this cache no longer exists.

I hope this helps to clarify. If you see any other optimization in the whole integration code, please let us know. Thanks!

[yesamer]

Thank you @martinweiler for the detailed explanation.