Multitenancy schema discriminator with OneToMany relationships - Wrong tenant reference leading to QueryException

[nexteam-silviot]

Hello!
We're facing the issue reported here in 2016, working with Multitenancy and schema discriminator.
When executing JPQL queries randomly it gets executed on the wrong tenant.

The patch attached in the Bug report above applies even on newest version (2.7.8) so I did apply the patch, recompiled the library and fixed the issue but I'm kindly request to please review the patch and apply it also on the official repo.

The issue seems due to a bug in the clone() function of OneToManyMapping class which is not cloning certain internal objects. When multiple threads modifies those objects (one of them is the tenant), it gets modified on the cloned ones too. Thus queries and persist() / merge() actions fail on a wrong tenant

I'm attaching here an example to help with debugging!

testmultitenancy.src.zip
mtfix.init.sql.zip

Prepare for the test

1) Create test schemas and tables with 2 tenants executing attached mtfix.init.sql file

2) Have 2 entities, Child and Parent using schema discriminator and having a OneToMany relationship
Find attached in src.zip Parent.java and Child.java files

@Entity
@Table(name = "children")
@Multitenant(MultitenantType.TABLE_PER_TENANT)
@TenantTableDiscriminator(type = TenantTableDiscriminatorType.SCHEMA)
public class Child implements Serializable {


@Entity
@Table
@Cacheable(false)
@Multitenant(MultitenantType.TABLE_PER_TENANT)
@TenantTableDiscriminator(type = TenantTableDiscriminatorType.SCHEMA)
public class Parent implements Serializable {

3) Import ParentDAO, TestFacade and TestResource classes from src.zip which implements the logic of the test

Steps to reproduce

TestFacade simply loads the Parent entity

System.out.println(Thread.currentThread().getName() + " => Parent loaded (id: " + id + ", tenant: " + tenant + ")");
Parent found = parentDao.load(tenant, id);
if (found == null) {
    throw new Exception("No entity loaded for id " + id);
}

Call TestFacade::execute() using multithreading with the two tenants, you will see that the function fails randomly with a QueryException.

ExecutorService es = Executors.newFixedThreadPool(5);
for (int i = 1; i <= 30; i++) {
    es.execute(testFacade.execute("tenant_1", 1));
    es.execute(testFacade.execute("tenant_2", 2));
}
es.shutdown();
es.awaitTermination(10, TimeUnit.MINUTES);

Example log

The query was supposed to execute on tenant_1 but the many to one relationship has a wrong tenant reference (tenant_2)

...
http-nio-8085-exec-119 => Parent loaded (id: 1, tenant: tenant_1)
...
26-May-2021 12:46:58.560 GRAVE [http-nio-8085-exec-119] org.apache.openejb.core.transaction.EjbTransactionUtil.handleSystemException EjbTransactionUtil.handleSystemException: 
Exception Description: The field [tenant_2.PARENT.id] in this expression has an invalid table in this context.
Query: ReadObjectQuery(name="readParent" referenceClass=Parent )
 Local Exception Stack: 
Exception [EclipseLink-6069] (Eclipse Persistence Services - 2.7.8.v20201217-ecdf3c32c4): org.eclipse.persistence.exceptions.QueryException
Exception Description: The field [tenant_2.PARENT.id] in this expression has an invalid table in this context.
Query: ReadObjectQuery(name="readParent" referenceClass=Parent )
	at org.eclipse.persistence.exceptions.QueryException.invalidTableForFieldInExpression(QueryException.java:757)
	at org.eclipse.persistence.internal.expressions.FieldExpression.validateNode(FieldExpression.java:327)
	at org.eclipse.persistence.expressions.Expression.normalize(Expression.java:3293)
	at org.eclipse.persistence.internal.expressions.DataExpression.normalize(DataExpression.java:371)
	at org.eclipse.persistence.internal.expressions.FieldExpression.normalize(FieldExpression.java:227)
	at org.eclipse.persistence.internal.expressions.CompoundExpression.normalize(CompoundExpression.java:226)
	at org.eclipse.persistence.internal.expressions.RelationExpression.normalize(RelationExpression.java:576)
	at org.eclipse.persistence.internal.expressions.SQLSelectStatement.normalize(SQLSelectStatement.java:1524)
	at org.eclipse.persistence.internal.queries.ExpressionQueryMechanism.buildNormalSelectStatement(ExpressionQueryMechanism.java:566)
	at org.eclipse.persistence.internal.queries.ExpressionQueryMechanism.prepareSelectOneRow(ExpressionQueryMechanism.java:1742)
	at org.eclipse.persistence.queries.ReadObjectQuery.prepare(ReadObjectQuery.java:793)
	at org.eclipse.persistence.queries.DatabaseQuery.checkPrepare(DatabaseQuery.java:673)
	at org.eclipse.persistence.queries.ObjectLevelReadQuery.checkPrepare(ObjectLevelReadQuery.java:968)
	at org.eclipse.persistence.queries.DatabaseQuery.checkPrepare(DatabaseQuery.java:622)
	at org.eclipse.persistence.internal.jpa.EntityManagerImpl.findInternal(EntityManagerImpl.java:937)
	at org.eclipse.persistence.internal.jpa.EntityManagerImpl.find(EntityManagerImpl.java:830)
	at org.eclipse.persistence.internal.jpa.EntityManagerImpl.find(EntityManagerImpl.java:696)
	at it.testmultitenancy.daos.ParentDAO.load(ParentDAO.java:30)
...

Thank you for your attention!