Aries JPA with EclipseLink: TransactionRequiredException on startup

[Jochen Walz <jo...@googlemail.com>]

Hi,

in our application, we frequently (not always) observe 
TransactionRequiredExceptions on startup:

2020-07-03T05:02:40,261 ERROR - Could not create or update entity in 
database
javax.persistence.TransactionRequiredException:
Exception Description: No externally managed transaction is currently 
active for this thread
     at 
org.eclipse.persistence.internal.jpa.transaction.JTATransactionWrapper.throwCheckTransactionFailedException(JTATransactionWrapper.java:96) 
~[!/:?]
     at 
org.eclipse.persistence.internal.jpa.transaction.JTATransactionWrapper.checkForTransaction(JTATransactionWrapper.java:56) 
~[!/:?]
     at 
org.eclipse.persistence.internal.jpa.transaction.JTATransactionWrapper.registerIfRequired(JTATransactionWrapper.java:133) 
~[!/:?]
     at 
org.eclipse.persistence.internal.jpa.EntityManagerImpl.joinTransaction(EntityManagerImpl.java:2237) 
~[!/:?]
     at 
org.apache.aries.jpa.support.impl.XAJpaTemplate.txExpr(XAJpaTemplate.java:60) 
~[?:?]
     at 
org.apache.aries.jpa.support.impl.AbstractJpaTemplate.txExpr(AbstractJpaTemplate.java:43) 
~[?:?]

We are running our application in Karaf 4.2.8, using the features jpa 
2.7.2, eclipselink 2.7.5, transaction 2.0 as basis for the persistence 
layer. Basically, the DAO methods are rather simple: the JpaTemplate 
service is injected using the respective Declarative Services 
annotation, and objects are then persisted with

jpaTemplate.tx(entityManager -> entityManager.persist(objectToPersist));

No TransactionType is defined, i.e. the default TransactionType.Required 
will be used.

When starting the system from the "clean" state, i.e. with the Karaf 
bundle cache not yet populated, we often - not always - receive the 
exceptions mentioned above. When such exceptions occur, and Karaf is 
restarted without deletion of the bundle cache, the exceptions will 
always reappear. When restarting Karaf with deletion of the bundle 
cache, sometimes the issue reappears, sometimes it doesn't.

The issue can always be reproduced by restarting the 
pax-transx-tm-geronimo bundle from the Karaf console. The issue can 
always be solved by restarting the 
org.apache.aries.jpa.eclipselink.adapter bundle from the Karaf console.

When investigating further, it could be seen that in the "error state", 
the XAJpaTemplate in org.apache.aries.jpa.support and the 
EntityManagerImpl and JTATransactionWrapper in 
org.eclipse.persistence.jpa hold different instances of the 
GeronimoTransactionManager (the EntityManagerImpl and 
JTATransactionWrapper still hold an old instance), while in the "good 
state", all these classes hold the same instance of the 
GeronimoTransactionManager. Obviously the 
org.apache.aries.jpa.eclipselink.adapter bundle doesn't care of changes 
of the transaction manager. Only when restarting this bundle, the 
services for EclipseLink are recreated and thus also receive the updated 
transaction manager. Depending on the startup order of bundles with the 
same start level (all involved bundles have start level 80), this 
situation often happens on initial startup. When the start order is 
fixed such that it results in the "good state", it remains "good" unless 
the bundle cache is deleted, because the bundle cache fixes the start 
order. When restarting with "clean", the game starts from scratch.

Now the question: does anybody know a solution for this problem? How can 
we grant that our application doesn't run into this situation on 
startup? Or is this something which can only be corrected in the Aries 
JPA Eclipselink Adapter code?

Thanks & Regards
Jochen