Adding a Timer Intermediate Throw event causes Hibernate issue

zaheena · October 30, 2018, 12:48am

Hello,

I am trying to implement a simple model that saves a value to the database, waits for 3 seconds and retrieves the value from the database.

Here is what my model looks like:
diagram_5

The timer is set to duration PT1M

In my SimpleSaveDelegate I have:

class SimpleSaveDeletegate implements JavaDelegate {

    @Override
    void execute(DelegateExecution execution) throws Exception {
        println("Saving to DB")
        SimpleSave simpleSave = new SimpleSave(name: "test")
        simpleSave.save(flush: true, failOnError: true)
        execution.setVariable("dbId", simpleSave.id)
        execution.setVariable("timeNow", System.currentTimeSeconds())
        println("Saved to DB")
    }
}

In my retrieve:

class SimpleSaveRetrieveDelegate implements JavaDelegate {

    @Override
    void execute(DelegateExecution execution) throws Exception {
        println("Retrieving from Database:")
        SimpleSave simpleSave = SimpleSave.get((Long) execution.getVariable("dbId"))
        println((Long) System.currentTimeSeconds() - execution.getVariable("timeNow"))
    }
}

This works fine for me when I do not use the Intermediate Timer Catch Event.

When I add the timer, I get the following stacktrace:

Saving to DB
Saved to DB
Retrieving from Database:
2018-10-30T00:45:12.090Z  ERROR  [org.camunda.bpm.engine.context]  ENGINE-16006 BPMN Stack Trace:
	Task_030y079 (activity-execute, ProcessInstance[5001])
	Task_030y079, name=Simple retrieve from database
	  ^
	  |
	IntermediateThrowEvent_14eosof

2018-10-30T00:45:12.098Z  ERROR  [org.camunda.bpm.engine.context]  ENGINE-16004 Exception while closing command context: Could not obtain current Hibernate Session; nested exception is org.hibernate.HibernateException: No Session found for current thread
org.springframework.dao.DataAccessResourceFailureException: Could not obtain current Hibernate Session; nested exception is org.hibernate.HibernateException: No Session found for current thread
	at org.grails.orm.hibernate.GrailsHibernateTemplate.getSession(GrailsHibernateTemplate.java:227)
	at org.grails.orm.hibernate.GrailsHibernateTemplate.doExecute(GrailsHibernateTemplate.java:183)
	at org.grails.orm.hibernate.GrailsHibernateTemplate.get(GrailsHibernateTemplate.java:256)
	at org.grails.orm.hibernate.AbstractHibernateGormStaticApi.get(AbstractHibernateGormStaticApi.groovy:59)
	at org.grails.datastore.gorm.GormEntity$Trait$Helper.get(GormEntity.groovy:514)

Has anyone encountered this before?

I was able to get past this error by using a new session when retrieving the information from the database like:

class SimpleSaveRetrieveDelegate implements JavaDelegate {

    @Override
    void execute(DelegateExecution execution) throws Exception {
        println("Retrieving from Database:")
        SimpleSave.withNewSession {
            SimpleSave simpleSave = SimpleSave.get((Long) execution.getVariable("dbId"))
        }
        println((Long) System.currentTimeSeconds() - execution.getVariable("timeNow"))
    }
}

But that gives me another stacktrace:

Saving to DB
Saved to DB
Retrieving from Database:
60
2018-10-30T00:51:33.394Z  ERROR  [org.springframework.transaction.support.TransactionSynchronizationUtils]  TransactionSynchronization.beforeCompletion threw exception
org.hibernate.SessionException: Session is closed!
	at org.hibernate.internal.AbstractSessionImpl.errorIfClosed(AbstractSessionImpl.java:133)
	at org.hibernate.internal.SessionImpl.disconnect(SessionImpl.java:467)
	at org.springframework.orm.hibernate4.SpringSessionSynchronization.beforeCompletion(SpringSessionSynchronization.java:122)
	at org.springframework.transaction.support.TransactionSynchronizationUtils.triggerBeforeCompletion(TransactionSynchronizationUtils.java:106)
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.triggerBeforeCompletion(AbstractPlatformTransactionManager.java:945)
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:787)
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:730)
	at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:150)
	at org.camunda.bpm.engine.spring.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:40)
	at org.camunda.bpm.engine.impl.interceptor.ProcessApplicationContextInterceptor.execute(ProcessApplicationContextInterceptor.java:66)
	at org.camunda.bpm.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:30)
	at org.camunda.bpm.engine.impl.jobexecutor.ExecuteJobHelper.executeJob(ExecuteJobHelper.java:36)
	at org.camunda.bpm.engine.impl.jobexecutor.ExecuteJobHelper.executeJob(ExecuteJobHelper.java:29)
	at org.camunda.bpm.engine.impl.jobexecutor.ExecuteJobsRunnable.executeJob(ExecuteJobsRunnable.java:88)
	at org.camunda.bpm.engine.impl.jobexecutor.ExecuteJobsRunnable.run(ExecuteJobsRunnable.java:57)
	at java.lang.Thread.run(Thread.java:748)
2018-10-30T00:51:33.397Z  ERROR  [org.springframework.transaction.support.TransactionSynchronizationUtils]  TransactionSynchronization.afterCompletion threw exception
org.hibernate.SessionException: Session is closed!
	at org.hibernate.internal.AbstractSessionImpl.errorIfClosed(AbstractSessionImpl.java:133)
	at org.hibernate.internal.SessionImpl.clear(SessionImpl.java:332)
	at org.springframework.orm.hibernate4.SpringSessionSynchronization.afterCompletion(SpringSessionSynchronization.java:143)
	at org.springframework.transaction.support.TransactionSynchronizationUtils.invokeAfterCompletion(TransactionSynchronizationUtils.java:168)
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.invokeAfterCompletion(AbstractPlatformTransactionManager.java:1001)
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.triggerAfterCompletion(AbstractPlatformTransactionManager.java:976)
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.doRollbackOnCommitException(AbstractPlatformTransactionManager.java:919)
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:789)
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:730)
	at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:150)
	at org.camunda.bpm.engine.spring.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:40)
	at org.camunda.bpm.engine.impl.interceptor.ProcessApplicationContextInterceptor.execute(ProcessApplicationContextInterceptor.java:66)
	at org.camunda.bpm.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:30)
	at org.camunda.bpm.engine.impl.jobexecutor.ExecuteJobHelper.executeJob(ExecuteJobHelper.java:36)
	at org.camunda.bpm.engine.impl.jobexecutor.ExecuteJobHelper.executeJob(ExecuteJobHelper.java:29)
	at org.camunda.bpm.engine.impl.jobexecutor.ExecuteJobsRunnable.executeJob(ExecuteJobsRunnable.java:88)
	at org.camunda.bpm.engine.impl.jobexecutor.ExecuteJobsRunnable.run(ExecuteJobsRunnable.java:57)
	at java.lang.Thread.run(Thread.java:748)

Would someone be able to tell me what I am doing wrong or point me in the right direction?

Thank you

Webcyberrob · October 30, 2018, 4:12am

Hi,

You may want to share your SimpleSave code…There is reference to Hibernate session management which is not part of Camunda code and thus must be in your SimpleSave… Something is going on within resource management in SimpleSave…

regards

Rob

zaheena · October 30, 2018, 4:20am

Hi @Webcyberrob

Thank you for looking! SimpleSave.groovy is a simple grails domain class. Looks as follows:

class SimpleSave {

    String name

    static constraints = {
        name(nullable: false, blank: false)
    }
}

Webcyberrob · October 30, 2018, 4:41am

Thanks,

The exception still looks like a Hibernate exception. Hence it appears that somewhere in your code base you are injecting Hibernate sessions. As I said, Camunda does not use Hibernate, so look through your code to identify where Hibernate transactions are being injected…

The reason a timer makes a difference is the timer introduces a wait state. Hence the first part of the process will occur in a separate thread of control to the second part. Hence this could explain why the hibernate resource is not available across the different thread contexts.

Have a read of async continuations or wait sates in the user guide…

regards

Rob

zaheena · October 30, 2018, 5:01am

Thank you @Webcyberrob!
I was using a DataSourceTransactionManager bean for my ProcessEngineConfiguration. I changed this to just use a PlatformTransactionManager and it works fine. I did not have to start a new session either to retrieve information from the database.
I am not entirely sure why this works. I will look into async continuations - but that is in case of errors right?

Thank you for your input.